Campervan Electrics: Build Your Powerhouse

Ultimate Guide to Campervan Electrics: Build Your Powerhouse

There are many complicated parts to any camper build. Perhaps the most intimidating are the campervan electrics.

An electrical system is expensive and dangerous. It’s a vital part since most of your devices and appliances will rely on it. And for a lot of people, properly figuring out what you need seems like a monumental, if not impossible, task.

But here’s the truth: How to build a campervan electrical system is not rocket science! It’s comprised of a few basic elements that work together to provide power.

We’ll start off with a thorough walk-through of the system in layman’s terms, then will show you how to calculate your electrical needs, and finish off with specific recommendations for each element of your system.

With these three steps, you’ll have all you need to complete your campervan electrics!

This information is based on a TON of research. But I am not an electrical engineer nor is it my profession to install off-grid systems. I have successfully done so for myself based on extensive research. I found a lot of the existing information was not practical nor phrased in ways I could understand. Which is why I’ve written this post, aimed at novices who want to build their own system. Be careful, be thorough, and take your time. You can do this!

Electrical System Basics: It’s All About Flow

Electrical systems are all about the generation, storage, and controlled transfer of electricity. When you understand these components, you’ll understand what you need to successfully build your campervan electrics.

If you already know the basic structure of your electrical system, you can jump down to the calculation of your electrical needs or the section on the specific parts to buy.

For those interested in learning more, let’s get started!

It will help to think of electricity as something that flows, just like water. An electrical system, like a water system, is all about controlling the flow.

Water is gathered (like electricity is generated) in a variety of ways. You can catch rain falling from the sky (solar panels) or suck it out of a nearby lake/stream (alternator), or hook a hose up to a running faucet (shore power and generators).

Dams are used to pool water into reservoirs for later use, just like batteries accumulate electrical power. The bigger the dam & reservoir (battery), the more water you can collect and store for later use.

Canals (wires) direct water to a specific locations. They are sized appropriately (wire gauge and voltage) depending on how much water you want to flow downstream to the plants/animals downstream (devices or loads).

Floodgates and barricades are used to stop/start the flow (switches) and to prevent floods and overflows (fuses and breakers).

Are you starting to see it? It’s all about flow! Now that you have a solid visual to work with, let’s dive a little deeper into each part.

Understanding this next section is key to creating your own DIY campevan electrical system. Once you thoroughly understand the fundamental parts, we’ll calculate your estimated electrical needs and then decide which parts are best for your system!

I. Generating Power

The origin point of electricity is the generation of power. It’s an extremely important role. If you don’t generate a sufficient amount of power, your electrical devices won’t have what they need to run. In other words, if you don’t have enough water, your stream/canals will run dry, and nothing downstream will get water.

There are four types of electrical generation to consider for your campervan build: (1) solar panels, (2) alternator charging, (3) shore power, and (4) gasoline/diesel generators.

Solar panels are a great way to leave campgrounds behind while stil staying powered up

Solar Power: The Ultimate, Modern Solution

I highly encourage you to maximize your solar usage. It’s an excellent way to provide campervan electrical power. One that frees you from the anchor and headache of needing electrical hookups. Don’t fret over booked campgrounds or quick overnight stays in who-knows-where.

Solar power allows you to achieve a level of freedom and convenience that doesn’t exist with conventional hookups.

Plus, solar power is free energy with a low carbon footprint! How can you beat that?

Some people are apprehensive about solar power, thinking that it doesn’t provide sufficient charge or will be a nightmare in poor weather.

While those concerns are valid, they fail to see what a well-designed solar system is capable of. Solar power can provide vast amounts of energy, which can be made to get your system through long nights and poor weather.

How is that possible? By doing two things properly: (1) get an appropriate amount of solar panels and (2) pair those panels with a proper amount of battery storage.

Going back to our water comparison, solar panels are just like rain catches. In areas with lots of rain (sunshine), you can get away with a small surface area of rain catches (solar panels). The less sunshine you expect, the larger the solar panels need to be.

To get an off-grid water system through period of drought, you can have larger-than normal cisterns to accumulate for dry periods. For solar power, increasing the battery size can allow for sufficient storage to get through times with limited sun.

Even if solar should cover your needs, it’s still wise to have at least one backup power source. That’s why these next sections are important.

Alternator Power: The Backup That’s Already There

One of the easiest backup methods is to connect your campervan electrics to the alternator of your rig. When the engine is running, the electricity is already flowing. You can tap into that very easily.

To make sure we’re on the same page, the alternator is a main component in nearly every vehicle. It uses the power from a running engine to generate electrical charge. It keeps your starter battery full and provides electricity to your headlights, cigarette outlets, and other electrical devices.

The best thing about this backup electrical source is that it’s already there! It’s relatively easy and inexpensive to hook up. The downfall is that you need to have the engine on (and ideally running at more than idle speed) to get any charge from it.

Are you currently shopping for a campervan? Don’t miss our guide to everything you need to know when comparing the Sprinter vs. Transit vs. ProMaster!

Shore Power: For the Luxurious Life

Some people use more power than others. If you want to have air conditioning, a microwave, hair dryers, or large electric water heaters, then you’ll probably want to stay at RV parks most of the time and have a way to connect to their hookups.

This is known as shore power. It’s simply the ability to run a cord from the high-power outlets at RV parks to your campervan’s electrics. There are specific devices meant for this connection and they are pretty straight-forward to attach to your system.

It’s like throwing a hose on a tap. Household taps (110V) provide a small trickle of electricity, while RV parks (usually 30amp or 50amp) provide a stronger flow.

Generators: Old Faithful

Finally, the backup of backups are the old-school gasoline or diesel generators. Notice how this is at the end of the list? There was a time when RVs depended on these and nothing else. Those days are in the past as they other three methods usually provide all you need.

Some people do still like to carry around generators for peace-of-mind. They’re also helped if you have a lot of electrical needs and want to stay away from campgrounds (although please be considerate of neighbors and realize that a lot of people in remote areas do not want to hear generator noise).

They come in tiny packages now and aren’t as noisy as they used to be. But hopefully you can design your build to avoid the need for a generator.

Hint: Pay attention to the next part carefully to avoid the need for generators.

II. Battery Power Storage

Generating power is like putting a funnel up when it’s raining or attaching a hose to a tap. It gives you immediate water but it doesn’t collect it for later use. Without proper storage, when the water stops flowing, your system immediately runs dry. Not ideal.

By incorporating a storage unit, like a cistern for water, you can create a reserve to be used later. With a sufficient amount of storage, you can get through a long time without collecting more water.

Batteries act like the cistern, but for electrical power. The larger the battery’s storage, the longer you can power your devices without needing to generate more power.

Think about it like this: If you travel with one small water bottle, you’re going to have to stop often to fill it up and can’t stay away from a water source for long. But if you travel with 30 gallons of drinking water, you can get through many days without finding a water source. You can drive through a desert (or get through rainy weather with solar panels).

Just like how water storage is rated in gallons or liters, battery storage is usually rated in amp-hours. The higher the amp-hours, the more electricity is stored for later use. Watt-hours may be used as well and are a very similar metric. We’ll review more about the relationship between amps and watts very soon!

Calculating the amount of amp-hours you will use in a normal day is incredibly important step to building your DIY camper electrical system.

Battery Technology Choices: Lead-Acid or Lithium

Another important factor is the battery technology you use: lead-acid (including flooded, Gel and AGM) or lithium (LiFeOP4). Let’s compare both options to see what’s best for your needs.

Cost is often what forces people to choose lead-acid instead of lithium. Lead-acid are more affordable, but you pay for them in other ways. For one, lead-acid batteries have to be replaced more often, especially if you don’t keep to their strict usage terms.

Realistically, while lead-acid is cheaper if you compare amp-hour ratings, there is a major flaw in any lead-acid battery: You cannot fully discharge them, while lithium can be fully discharged. In fact, most lead-acid will suffer damage is discharged below 50% and even the best (AGM) can only go down to 80%. This DOES apply to those lead-acid marketed as “deep cycle” batteries.

To put it in water terms, it’s like buying a 20 gallon reserve but having to keep 10 gallons in it at all times. Or else it will never store water as well ever again. Why not just get a better 10 gallon reserve instead?

Another reason lithium is the preferred battery for campers is that they can handle a more rapid charge and discharge. Additionally, some lead-acid batteries can expel dangerous fumes. You’ll want to seek out the gel or AGM (glass mat) lead-acid batteries to avoid the noxious off-gassing.

And the final reason lithium batteries are superior is that they’re significantly smaller and lighter (often 4 times less weight). And both of those factors are pretty important for campervan builds!

So what’s right for you? If you don’t need a lot of energy storage, a gel or AGM lead-acid solution might be acceptable. But if you do need a lot, then you’ll want to pencil in a budget for lithium storage. Keep in mind that this is a vital part of your van and not one where you should look to save money on.

How can you calculate the energy you’ll need? We’ll get to that shortly.

III. Transferring Power

At this point, we’ve covered how to generate power and how to store it. The final step is how you connect those parts and send it to the things that need it.

It can be helpful to think of a camper’s electrical system as having two parts: the “supply” side and the “demand” side.

The supply side takes the energy inputs and uses them to charge the battery. But there’s a catch: you can’t simply connect anything directly to the battery. That could result in catastrophe, like putting a 5-gallon bucket into a raging river.

Specific devices are used to carefully control the flow of electricity into the battery. And these devices are very important. They can also be a little tricky because they can be combined for multiple purposes.

Solar panels are connected to a battery through a solar charger. That one is pretty straight-forward, you just have to make sure that the solar charger is properly rated (usually in amps) for the amount of solar power you have.

The alternator can be connected in many ways. The one that I prefer due to its simplicity is a dual charger, which is called that because it acts as the charger for the solar panels AND the alternator. It can even charge your vehicle’s starting battery from your solar panels. Pretty cool. The other option is to connect the camper battery to the alternator through a battery isolator and relay.

Shore power is connected to the battery through a shore power device also called a charger. It’s basically just a connection point which looks just like an outlet. But it allows a reverse flow of electricity (into the battery instead of out from it). It goes like this: the RV park outlet connects to your high-amp extension cord, which plugs into your shore power charger input, which feeds into your battery. You can often use these on “regular” household 110V outlets too; it just won’t charge very quickly. It’s like a trickle from a small tap compared to a fire hose.

Generators would connect through the shore power charger input as well. The flow goes from the generator, through a high-amp extension cord, to the shore power input, to the battery.

Since this “supply” side is for the entire system, the amount of electricity is quite high. Not only will you need to use large-diameter (low gauge) wire, you’ll also need to use large fuses or breakers between each charge system and the battery. ANL fuses or re-settable breakers are the two methods many campers use.

The “demand” side of your electrical system is pulling stored power from your battery and feeding it to the devices as they need it. The best way to connect this demand side to the battery is through a fuse box. It allows you to connect many devices to your battery in a well-organized manner.

The wiring and fuses on the demand side are going to be smaller. That’s because each device should only pull a fraction of the electrical power that is stored.

You probably figured this out, but determining the correct wires and fuses is a vital part of campervan electrics safety. But I urge you to put this on the back-burner for now.

First understand the components and how they work together (what we’re going over now). Calculate your electrical needs (which we’re going to cover). And focus on getting the major components in your hands.

You can easily add the proper wires and fuses after that. As a matter of fact, a lot of the manufacturers of the devices tell you EXACTLY what to use.

IV. Converting Power Types: AC Power Inverter

Generating, storing, and transferring power are three necessary parts to any campervan electrical system. This section is about power inverters, which is an optional part. One that most people want.

First, a little primer on what a power inverter does and how to decide if you need one.

There are two primary types of power in today’s world: alternating current (AC) and direct current (DC). AC is what you deal with most often: the three-prong outlets at any house or business. DC is what your car runs off of, what boats use, and as you might have guessed, what your campervan electrics provide.

There are many technical differences between AC and C power, but the main difference is the voltage. AC runs at 110-120 volts (in North America) while DC most commonly runs at 12 volts (approximately). Both AC and DC can be designed to run at different voltages, such as the 240 volt plug for dryers and fridges at home or the 24 volt that some DC systems use.

As far as campervan electrics go, DC is basically the “raw” power coming off of the battery. An AC power inverter takes the direct current (DC) and transforms it into alternating current (AC).

Do you need an inverter or AC power? Not necessarily. If you only have DC devices and appliances, then there is no reason to install a AC power inverter.

A lot of devices can use DC power. Think about anything you can plug into your vehicle’s cigarette lighter, anything that can run off of USB, or anything that has a “barrel” plug connector (circular opening with a pin in the center). Common examples include phones, tablets, cameras, and other small electronic devices.

Camper appliances often run off of DC power too. Which is the biggest difference between camper appliances and household ones. Ever wonder why people spend a lot of money on camper fridges that look a lot like the cheap fridges found in dorm rooms everywhere? Using DC power is the main reason.

Why do people spend so much on DC appliances if you can simply get an inverter to power AC devices? It’s because an AC inverter wastes energy. You only want to turn them on when necessary and use devices on AC when it’s not possible to use DC. Going back to our water comparison, using AC power in a campervan is like using a leaky pipe. It will move water (energy), but you’re constantly losing a little bit.

Some require AC power. If it has a connector that MUST be plugged into a household outlet, then it probably needs AC power. Common items that require AC power include large blenders, some computers, slow-cookers or instant pots, and hair dryers. Things that you can’t charge off of USB or barrel plugs.

Now is the time to think carefully about what you want in your campervan. Is there anything that needs AC power?

If you do need it, then you have to determine what size inverter you need, which is measured in wattage. The higher the wattage of the AC device, the bigger and more expensive the inverter will be.

Devices that require those massive inverters will use a lot of energy, so you’ll either need to rely on shore power or get a massive solar array with substantial battery storage.

That’s why you’ll need to carefully consider using things like induction stovetops and electric water heaters. They sound convenient, but between the inverter cost and the energy usage, using propane cooktops and heaters might make more sense.

Save your money and put that monthly rental fee in your own piggy bank

What to Purchase for Your Campervan Electrics

Now we’re getting to the fun part! I can tell you from experience, receiving the electrical components was simultaneously one of the most exciting and nerve-racking parts of a van build.

But one day, those parts will go from the factory, to your garage, and finally to their forever home in your camper! You’ll be all powered up and ready to roll in style to your next destination.

Can you envision it? Isn’t it exciting?!

But there is one more step to take before purchasing the parts. You have to calculate your electrical needs (load). This will give you an idea of how much power you should generate and store. And perhaps more important, it will help you understand what devices you can use in your campervan.

So let’s talk about how to calculate your electrical needs. Then we’ll go over some of the specific options for electrical components and review some of the usual packages of components that often fit together.

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How to Calculate Your Electrical Load

The calculations for campervqn electrics may seem daunting, but take a step back and think about it. We’re trying to build a system to power your things. Calculating how much power you need is simply figuring out how much power your things use. That’s it.

Since batteries are rated in amp-hours, this is a good unit to do this calculation in. Knowing the amount of amp-hours you expect to use in a typical day is exactly what you need to help determine the battery, solar panels, and other electrical parts you need.

Thankfully this is not that complicated and relies on only a few numbers. Wattage, voltage, and amperage all work together in a simple formula: watts divided by volts equals amps. Most devices will provide the watts and the volts, so you can calculate the amps. Or they’re simply provide the amps!

Once you have the amps, multiply it by the expected hours of use, and you’ve got amp-hours.

Our Journey: Light at the End of the Tunnel

Now, as much as I’d love to tell you that we’ll figure out what you need down to the last amp-hour, that’s basically impossible. These calculations will be full of estimates. So don’t get too caught up in the details. In general, try to overestimate your usage and pay attention to the things that use a lot of power.

I know spreadsheets are loathed by many. But this is the point where I recommend busting one out. If you prefer, paper and pen works just fine too. But you’ll need a calculator. Whatever method, make sure to save this information. It will be useful down the road (wire and fuse related calculations).

In one row, add the following labels: Device, Wattage, Voltage, Amperage, Estimated Use (Hours), Amp-Hours. These six columns will tell you all you need to know to calculate your amp-hours. You will be able to find this information on the devices themselves, on power cords/blocks, in the owner’s manual, or by performing a Google search.

Under the device column, list the things you want to power in your van. Try to be thorough. Separate these devices into three groups, as listed below.

In the first section, write down any DC devices. One row for each device. You should be able to locate the wattage of these quite easily and you already know that they run on 12 volts (because that’s your DC power system). Take the watts and divide by 12 volts and you have the amps! Multiply the amps by the estimated hours (or fractions of hours, e.g., 30 minutes equals 0.5 hours), and you’ve got amp-hours!

In the next section, list down any AC devices which do NOT have a power brick or AC/DC adapter on them (just a wire connecting to an AC outlet). These devices typically do not list their amperage and instead will give you wattage. Take that wattage, divide by 12 and you’ve got your DC amps! Multiply by the estimated hours to get amp-hours.

Finally, the challenging ones: list your AC devices which use a power brick or AC/DC adapter. You’re looking for the “output” figures here and you should find amperage and voltage. The reason these are difficult is because they change the voltage. But some do incidentally use 12 volt. If that’s the case (they use 12 volts), the amp number they provide is the one you need. Multiply by the estimated hours to get amp-hours.

If you find any of the output figures are NOT in 12 volt, then you’ll need to convert. Remember that watts divided by volts equals amps? This translates to volts times amps equals watts. Use this to find the watts: take the device’s listed output voltage times its listed amps. Write that number down in your “watts” column. Now do the same calculation you did for the DC devices (divide the watts by 12 volts to get amps). Multiply that number of amps by the estimated hours to get amp-hours.

Here is an example of what your spreadsheet could look like:

Once you have all of the amp-hours determined, add those up and you have your daily amp-hour usage! That’s a big deal!

Did you have a problem finding the right figures for some devices? If it’s a small DC device, I wouldn’t worry too much about it. Put in an estimate based on other devices and move on.

If you couldn’t locate the figures for a device that might use a lot of power, then try to perform a quick google search for it. If you can find two out of the three magical numbers (watts, volts, or amps), you should be able to find amp-hours now using one of the three above methods. Or you might be able to find the exact amp-hours that the devices battery has.

Estimating the time used can be a bit challenging. Many devices, like computers and fridges, don’t run on full power all the time. And knowing exactly how much they’ll use can be a challenge. For laptops, you should be able to find the battery size in amp-hours (or milliamp-hours, which is 1/1000 of amp-hours). Think about how often you charge your computer, and that gives you a reasonable estimate. For example, if your battery is 6 amp hours and you charge it once per day, then you typically use 6 amp-hours in a day.

Fridges depend heavily on how big they are, what you put inside, how often you open them, and the ambient temperature. I’d say going with about 50% usage is a pretty reasonable number for calculating your overall energy use. It’s unlikely it should run that much, but you’ll want to be ready for it in case it does. Hopefully you’ll be using an efficient DC fridge which shouldn’t use all that much energy anyway.

Vent fans, which use differing amounts of power on different settings, are another challenge. MaxAir vent fans (a popular choice) are extremely powerful and I would say that very few people use these on high for too long. I’d probably add in somewhere around 30-40% power for 15-20 hours per day, but feel free to draw up your own assumptions.

Hopefully you have a decent idea of how many amp-hours your system is likely to use. You probably found that the small DC devices hardly put a dent in it (running a vent fan for 24 hours might use less than 10 amp-hours), while big AC appliances can eat into the power rapidly (an electrical water heater might take 100 amp-hours for one cycle).

Use this information to re-think your electrical devices. Perhaps you noticed that a big AC device you wanted to bring uses more power than all other devices combined. It might be time to consider how realistic that device is. On the other hand, maybe you thought you must get a very small DC fridge. Maybe you can step that up a size? Or add more lights!

With your amp-hours in mind, we’re ready to look at the options for your campervan electrics! This is what it all comes down to.

You might feel like you aren’t prepared to purchase anything yet. I understand the apprehension, but I also urge you to pull the trigger. Some devices are in high demand right now; we had to wait months for a few of our major parts. And let me tell you, having 80% of the electrical parts will not cut it.

So rip that bandaid off! Figure out the amp-hours you need, take a realistic look at your budget, and buy your parts! That’s what having a campervan is all about. Taking life by the horns, not letting it slide by. You can do this!

Battery Storage

Whew, that was an intense calculation. And you’ve already learned so much. Now you’re ready to figure out your battery and power-generation choices! Give yourself (or your van partner) a big ole high-five.

Now that you know how many amp-hours you’re going to use in a day, you have an idea of how much battery storage you need. So let’s start off with the battery selection. We’ll go over how you’re going to generate the power next.

It is VERY wise to build in some large cushions to your numbers here. All electrical systems have inefficiencies, meaning they don’t provide the exact amount they’re supposed to. Each connection and wire will lose a bit of power through heat; the longer the wire, the more loss. In the water metaphor, each canal has some evaporation due to sunlight. Each turn in the canal has a bit of spillover to the side. AC devices even more so due to the inverter.

You’ll also have to consider how long you want to be able to go without charging. If you want to live on solar alone, then you’ll need storage to get through rainy days. Some sunlight will trickle in, but plan for the worst. A conservative rule of thumb is to have at least 2-3 days’ worth of power in your batteries. And at least 10% loss trough inefficiency.

Some people might say this is overkill, but they’re probably the ones who will also tell you solar panels don’t work well enough. I say go a bit overkill with battery storage and have the peace-of-mind that comes with sufficient power that only relies on the sun to be out once every few days.

If you calculated that you will use around 50-80 amp-hours per day, then I recommend battery storage in the 150-200 aH area (if using lithium; you’ll have to DOUBLE that for most lead-acid). If you have a lot of electrical needs and are in the 200 amp-hour per day range, then you probably want to shoot for 400-600 aH of storage. Keep in mind that not only is this expensive, it’s also heavy and takes up precious cargo room.

When you shop for batteries, you’ll find that they come in specific sizes, usually around 100, 150, 200, or 300 amp-hours. If possible, get one battery to fulfill all of your needs. But if you’re in the 400aH or more range, then get multiple batteries of the same amp-hour and voltage rating. To get 400aH, get two 200aH; for a 600 aH system, get two 300aH or three 200aH; etc.

Once you’re ready to wire everything, you can connect them together. Again, I urge you to avoid getting too caught up in the specific details of wiring them, but if you connect them in parallel (not series), you will keep their 12 volt property and will have no issues.

Do your needs seem too high? Go back to your device list and see what’s hogging the electricity. Electrical water heaters are giant energy drains. LED lights, fans, and small electronics are usually negligible. What are the power hogs and do you need them?

If you still simply can’t match your electrical needs with battery storage, you’re not alone. That’s what shore power and generators are for. Do your best to cover the essential needs (in case of shore power outages or a desire to be off-grid for a few days), but at the end of the day, if you need shore power to be comfortable, use it!

There are TONS of batteries on the market. What should you buy? I’ve already scoured the markets and have done the research for you. These options are the best of the best, and offer the right one for any budget.

Let’s check out the best options!

Best of the Best: Battle Born Batteries LiFePO4 Deep Cycle Battery – 100Ah 12v

This isn’t the cheapest battery on the market, but it might just be the best. Featuring a built-in battery management system, green energy batteries, and designed/assembled in Nevada, these batteries are a great choice for those who want nothing but the best.

Editor’s Choice: Ampere Time 12V 200Ah Lithium Iron LiFePO4 Deep Cycle Battery

There is no better feeling then getting a lot of bang for your buck. That’s exactly what this lithium battery does. Not too long ago, the price of this battery would have been unthinkable for lithium. But it is! And it still comes with a built-in battery management system to protect this vital piece. Ampere Time offers a range of batteries, including high amperage ones meant to power devices that require rapid discharge at high amperage rates. Check out their full line here!

Best Budget Option: Weize 12V 100AH Deep Cycle AGM Battery

If a lithium battery doesn’t fit your budget right now, then this AGM lead-acid from Weize is your next best bet. This will get you plenty of power, just remember that you should get a battery with more amp-hours than your actual usage since they can’t be fully discharged.

Solar Panels: Harness the Power of the Sun

Now that you have a decent idea of how much power you’ll use and how much storage you’ll get, it’s time to consider the generation of power. With any luck, you’ll have enough space on your roof to take care of 100% of your needs with solar alone. Just remember to plan for overcast days and other times with shade (parking under trees, in a shade structure, etc.). That’s done by getting a proper amount of panels and a sufficiently large battery.

Solar panels are rated by their wattage. Since we’ve already calculated the amp-hours, we can reverse that and find what amount of watts you need. Watts divided by volts equals amps, which means that amps times volts equals watts!

Take your amp-hours and multiply by 12. This is the total watt-hours you’ll use in a day!

That number looks pretty big, right? If you plan on using 60 amp-hours per day, then you have 720 watt-hours. Wow, that’s a lot.

But divide that by the number of hours you can safely plan on sunlight being around. Once again, this is a truly imperfect calculation. How can you possibly determine how many hours of sunlight you’ll get? And more importantly, your solar panels, like all electricals, will have inefficiencies.

The solar panel inefficiencies are multiplied by the fact that your panels probably won’t be perfectly facing the sun all day. You’d have to have a very special roof rack for that; it would have to angle the panels to the sun and track it across the sky all day.

So what should you use? I’d say most people could plan on a maximum of 8 hours total sunlight. Shooting for a conservative estimate of efficiency loss, I’d take that down to 4-5 hours of actual charging at anywhere near 100%.

So going back to your watt-hours, if you want to go with a very conservative estimate, take your watt-hours and divide by 4.5. This gives you the amount of solar panels in watts that you need to charge fully in 4.5 hours.

You might notice that some devices take a lot of power. If you won’t use those daily, then pull those out and re-examine your load. Maybe you can cover those “extreme” days, but build your whole system based on the days without it. That’s a call that’s tough to decide.

Here are some examples for how the solar panel size could be calculated (at the bottom):

For example, a 12 volt system that uses 50 amp-hours in a day has 600 watt-hours. 600 watt-hours divided by 4 hours of charging equals 150 watts. So you need 150 watts worth of solar panels to provide this 50 amp-hour figure through solar alone. You’ll get more than this if sunlight is good and less if sunlight is bad. But just 2 hours of near max sun can give you all you need for an entire day. That’s a pretty solid figure.

Should you plan on making the solar panel array larger than one day’s worth of use? Maybe, but just remember that we used 4.5 hours of charging. If you’re getting closer to 6, then you’re already building in a a big cushion for the solar panels. More than likely, you’re better off putting the extra funds into battery storage instead. Those extra hours of solar charging will get properly stored and can be tapped into when the sun is down or if the weather turns.

Once again, this is not a perfect science. The best bet is to use conservative estimates (over-estimate your electrical usage, underestimate the charging hours) and also be aware of the conditions. If poor weather is expected ahead, power things up while the sun is shining and get the batteries full while you can. Don’t use unnecessary electronics on the worst days. Dirty solar panels will reduce charging abilities.

Now that you have the amount of solar calculated, how does that work out when you buy individual panels? Just like batteries, you might have to wire up different solar panels to get the specific wattage you desire. You will also need to match up the physical area on your roof with the size of panels. Solar panels can be mismatched (use differing wattage together), but it’s best to get the same wattage panels when possible.

After many hours of research, we’ve come down to this short list of the best solar panels on the market. We’ve done the work for you. Now it’s time to get these in your shop and get them mounted so you’re ready for your next adventure!

Best of the Best: Topsolar Flexible Solar Panel 100W 24V/12V Monocrystalline

This solar panel is about as thin as they come, making it possible to hide your solar system from the outside world. Who doesn’t want to be more stealth? The only downfall is that by mounting these directly on your roof, you lose the ability to ventilate and cool your panels from below. Still an excellent choice from a trusted brand.

Editor’s Choice: Renogy 12 Volt Solar Panel 100 Watt High-Efficiency Monocrystalline

Renogy is a big name in the solar industry. This 100W panel uses the most efficient monocrytalline technology available and combines it with a sturdy frame for mounting on nearly any roof or roof-rack you have. With extremely competitive pricing and a brand that stands behind their product, this is a no-brainer.

Budget Option: HQST 100 Watt 12V Monocrystalline Solar Panel

If your budget is tight and you want to save a few bucks, then the HQST solar panels are right up your alley. Although the brand doesn’t have the same recognition that others do, it’s still highly trusted on Amazon and uses the same technology. I’m positive this will serve your needs well.

Click here to see why we think camper vans are the ultimate adventure vehicle! Don’t forget why you’re doing all of this!

Chargers: Solar, Dual DC, and Shore Power

There is an important part between your solar panels and battery: the solar charger. This is not an optional piece of equipment.

Other chargers, however, are optional. As stated earlier on, it is wise to have backup power generation even if your solar should be able to cover your needs. Be ready for the worst case scenario.

Now what if you want an additional power source? The main two options that are good for campervan electrics are (1) a charger which connects to your van’s engine battery and alternator and/or (2) a shore power connection, allowing you to use a plug to charge up your campervans electrics. We’ll go through these in a second.

Solar Chargers: Safely Connect Your Panels to the Battery

Let’s focus on solar chargers first. There are two types of solar chargers: Pulse Width Modulation (PWM) and Maximum Power Point Tracking (MPPT). Unless you’re doing a very small-scale solar array (100W or less), I highly recommend getting an MPPT solar charger. They’re more efficient and PWM require matching voltages. MPPT chargers often come with more features, like a bluetooth connection to monitor your charging.

And the MPPT charger you should get, once again, is determined by the size of your solar array. A larger solar array will put out more energy and will require a higher-rated charger.

Solar chargers, as they’re so aptly called, are rated in amps. To determine the solar charger you need, you’ll need the amperage of your solar array. Watts divided by volts equals amperage. If you decided on a 200 watt solar array, running at 12 volts, that’s just under 17 amps.

Here’s the catch: You want to leave a buffer between the total rated amperage of your charger and the amps your solar array puts out. About 25%-30% cushion is ideal. So this 17 amp solar array (200 watts at 12 volts) should have a solar charger of 17 times 130%. More precisely, it’s 16.67 * 1.3 = 21.67. Could you go with a 20 amp charger? Probably, but I would go ahead and shoot for 25 or even 30 to be safe.

Here’s a general idea of the proper charging size based on the wattage of your solar panels (in 12 volts): 20 amp charger for up to 260 watt solar panels; 30A charger for up to 400W of panels; 40A charger for up to 520W of panels; 60A for up to 800W; and 100A for 1300W of panels.

Here are the recommended solar chargers (but keep reading this post before you buy these; you might want a dual charger instead):

Best of the Best: Victron Energy SmartSolar MPPT 100V 30 amp

If you’re looking for the best in solar chargers, then Victron is where you want to go. They have a full array of chargers that can suit almost any size system. This brand is one of the most-trusted solar energy brands on the market and you’ll see these little blue boxes in builds across the country. With that sort of brand recognition comes a premium price tag.

Editor’s Choice: Renogy Rover 40 Amp 12V/24V DC Input MPPT Solar Charge Controller

Renogy is another well-trusted brand. One that myself and thousands of others have put inside of our rigs. Their customer service and support staff is excellent; their products are reliable; and best of all, they are a great value for what they offer. This 40A option will deal with most campervan solar systems without blinking twice.

Budget Option: Renogy Wanderer Li 30A 12V PWM Negative Ground Solar Charge Controller

Now I know I said MPPT chargers are ideal, but you simply can’t beat the price point on this little guy. Especially when it comes from a brand that a lot of people know. This 30A solar charger will take care of your needs and keep you topped off.

Engine/Alternator Charging

The engine/alternator chargers can be done in two ways. First is through a battery isolator and relay. Many people use this type of system to add a second battery to vehicles/boats/campers for all sorts of purposes. These second batteries (ones that are NOT used to start the vehicle) are known as “house” or “leisure” batteries. That’s because they’re used for more house-like or leisure-like demands.

The second way is to get a dual DC-DC charger. This type of charger connects two charging methods to the batteries. You connect your solar panels AND your engine alternator to this charger, which then runs power to your campervan battery (the “house” or “leisure” one).

In some cases, these dual chargers will also use the solar panels to charge the vehicle battery too! It’s a nice backup charging to have and you should never need a jump start again. Imagine solar panels acting as your emergency jump! Pretty cool huh?

The downfall is that if the charger goes out, you lose both charging methods. While if you use a separate solar charger and a separate charger from the alternator, then if one goes out, you still have the other.

The dual chargers are my preferred method because the reality is that a dead vehicle battery is more likely that a bum charger. Especially if you buy the proper charger for your system and don’t overrun it.

Editor’s Choice: Renogy 12V 30A DC On-Board Input MPPT Battery Charger

Once again, Renogy comes in clutch with this dual charger. And to be honest, they are one of the few trusted brands offering this system. But it can handle a lot of power and will keep your vehicle and house batteries topped off, using your solar panels and vehicle alternator for both batteries. It can detect when your vehicle is on to swap over to alternator power.

Isolator and Relay: KeyLine Chargers 12V 140 Amp Dual Battery Isolator Voltage Sensitive Relay

It’s nice when things come together easily. And that’s what you get with this little package from Keyline, a trusted brand (just check out those reviews!). Isolator and relay in one, plus all the wires and connectors you need! Just make sure the wire is sufficient length for your needs. If not, check out the isolator options without the kit.

Shore Power & Generators

For those who want to use those high-draw electrical devices on a regular basis, there is no substitute for shore power. It’s like being hooked up to a hose at all times, and if you’re staying at an RV park with 30 amp or even 50 amp plugs, it’s more like being connected to a firehose. Use up all the power you want.

If you only need 30 amps (most people), just know that you can always hook up to a larger source and it will safely limit the charge to your system. That’s a giant part of what this piece does!

Best of the Best: Victron Energy MultiPlus 2000VA 12-Volt Pure Sine Wave Inverter 80 amp Battery Charger

Victron is, once again, going to the top of the list. But they like to do things a bit differently. Rather than making shore power connection separately, they combine it with an AC power inverter. So not only are you paying for Victron’s supreme price level, you’re also buying another device built in.

If these meet your metrics and your budget, you absolutely cannot go wrong. Pay attention to the wattage of the inverter and the amperage of the charger to make sure you get the one that’s right for your system.

Editor’s Choice: Samlex America (SEC1250UL) 50 Amp Battery Charger

This 50 Amp charger can handle a lot of power and doesn’t break the bank. It will transfer the charge from your AC outlet at your home or campground into your campervan’s battery. Perfect! Make sure it’s paired up to at least 200Ah of lithium battery or 400aH lead-acid; if you have a smaller battery capacity, then go with a 30 amp solution instead.

Budget Option: Victron Energy Blue Smart IP65 12-Volt 15 amp Battery Charger

If Victron’s inverter/charger is pushing it and you don’t have serious amperage needs, then this Victron charger is a good option. It’s limited to 15A, but they also make a 25A version of the same device. Best of all, it connects through Bluetooth to a device so you can safely monitor your charge. It also steps down any 30 or 50 amp connection for use n your system.

Generators

A shore power connection will also allow you to connect a generator to your campervan electrics. While I urge you to reconsider using a generator in today’s world, I understand that some people get a lot of peace-of-mind from them. There are some pretty incredible designs out there.

Best of the Best: Honda Power Equipment EU1000I 1000W 120V Gas Power Generator

It’s nearly impossible to beat the Honda brand when it comes to engine design, and portable generators are no different. While you’re paying for that brand recognition and reliability, your dollar doesn’t go as far as it would with other brands. The wattage is fairly low for the price tag, but this should last you many years.

Editor’s Choice: A-iPower SUA2000iV 2000 Watt Portable Inverter Generator

Now here is some bang for your buck. This little guy supplies 2000 watts in a tiny package and will keep your system powered up in the worst of all situations. All without making you break your budget. Perfect!

Budget Option: PowerSmart 1000 Watts Portable Generator

If you feel like you really need a generator but don’t want to shell out much cash, then here is a solid option that has been trusted by many. It’s not as small as the other options on the market and likely won’t last as long as a Honda version would, but it’ll do the trick!

AC Power Inverter

The final major component of campervans electrics is the AC inverter, if you decide you need one. Make sure to find an inverter that uses pure sine technology. Besides that, the most important consideration for the AC inverter is what amount of watts you need.

To figure this out, you’ll have to scour your AC devices and find their wattages. Things like a hair dryer, large blender, or water heater will be the main offenders. An air conditioner can really draw some power too, although hopefully you have a DC-powered one.

Once again, you need to build in some buffer here. You should get a power inverter that’s at least 30% higher than your devices’ watts. So for a device that uses 1500 watts, you’ll need an inverter that is 1500 times 130%, which equals 1950. This means you should get a 2000 watt inverter (2kW). Also, when you use this 1500 watt device, you should not have anything else connected or powered by the inverter.

To be clear, this is the continuous use power rating. Inverters are typically rated for continuous use and for surges. The surges amount should handle about double of the continuous and that’s important for some devices that have surges at start-up.

If you don’t really have a lot of AC devices, you can always get a very small power inverter and keep it around for emergencies. Something like a 200 – 300 watt inverter doesn’t take up much space and can come in handy for those small AC devices. Just don’t overuse them. Electricity and inverting power shouldn’t be taken lightly.

This is an area where video game systems, high power computers, and large TVs can really take a toll on your electrical system and the budget for it. A small inverter is fairly reasonable in price, but a larger inverter, say 4000 watts or more, gets to be quite pricey. Not to mention the space and ventilation they need in your van.

So take a hard look at that device list. Think about what you’re going to need and what you want to build this electrical system for. Plan ahead for the future.

Best of the Best (Charger/Inverter): Victron Energy MultiPlus 2000VA 12-Volt Pure Sine Wave Inverter 80 amp Battery Charger

This is a repeat from the shore power section. That’s because Victron likes to use these two devices together. It’s still the best option if you’re shooting for a 2000 watt inverter, want shore power, and budget isn’t much of a concern.

Best of the Best (Inverter only): GIANDEL 4000W Pure Sine Wave Power Inverter DC12V

If you just want a sizable inverter from a solid brand, then look no further than this Giandel 4000W inverter. It has 4 plugs and plenty of protection built-in.

Editor’s Choice: Renogy 2000W Pure Sine Wave Inverter 12V DC

Once again, Renogy is going to be my top recommendation. It fits the bill perfectly for a lot of people, offering sizes from 700W up to 3000W, with solid built-in protection, and a remote switch you can install somewhere easily accessible. Two ventilation fans keep things cool while in use. Just check out the amount of reviews these things have!

Budget Option: BESTEK 500W Pure Sine Wave Power Inverter DC 12V

If you’re only looking for a small inverter, then this Bestek 500W inverter is likely a good choice. It features many ways to connect to power. You can install it permanently using ring connectors, hook up to nearly any 12V battery for a moment with clamps, or plug into a vehicle’s cigarette lighter. And 500W is still a lot of power!

And there you have it. That’s the list of the major elements to your campervan electrics!

Still not sure what to get? No worries. Here are some general recommendations:

(The prices on these products change rapidly and depend on the actual amount of batteries and solar panels plus the amperage/wattage of the chargers/inverters you choose. Also, now is a time when I would consider that you still have wire/fuse/breaker costs to add in. High-amp wires, terminals, and the tools needed for the system can get expensive as well. I’d factor in somewhere around 10-20% of the cost of these systems to properly wire them.)

Best of the Best: Your Ultimate Power Package ($3,500 to $6,000 or more)

The total cost of this package might shock you, but you’ll be getting a high-powered system that’ll be ready to run nearly any device. It starts off with a large array of excellent batteries and solar panels, charged through a Victron solar charger and a very sleek Victron shore power and inverter in one device. With all this power, it’s unlikely you’ll need an alternator charger too, but you can always add it.

Add more batteries to increase your amp-hours, and you have your choice of solar panels depending on if you want the sleek look or want to prioritize cooling/efficiency. You can always bump up the inverter/charger size if your needs are higher. One final thought if you’re considering this package: You might want to look into making it a 24V system to allow for quicker charging and discharging.

Editor’s Choice: A Solid System with Reliable Products ($1,200 to $2,500)

This is a pretty solid package that will likely serve a lot of people well. Starts off with a battery that has one of the best values around, powered by proper solar panels, charged through the awesome Renogy dual charger (running off the vehicle alternator and the solar panels). Add in a separate inverter and shore power charger, as desired.

Best Budget Package: Power Up Small Devices in Style ($500 to $1,300)

If your electrical needs simply aren’t that big, then don’t waste your budget on them! Get a nice, sealed battery, throw on some solar panels and a charger, with a connection to your vehicle’s alternator as a backup. You’re good to go! Start exploring!

Summary of DIY Campervan Electrical System

You’ve done it! Reached the end of this long article that’s been PACKED with information.

Hopefully by now you have a good understanding of how electricity can flow through your campervan’s system. It’s all about generating, storing, and transferring the right amount of power.

You should also be able to calculate your electrical needs, while keeping in mind that these are imperfect figures and you shouldn’t get too lost in the details. After all, budget is likely going to be the biggest consideration for most people. If not, go pay a professional!

The recommendations listed here are based on a serious amount of research. You can have faith and peace-of-mind knowing that I’ve scoured the manufacturers, the consumer reviews, and every detail about each device to lead you the right way.

Now it’s time to make your dream happen!

Get these products in your hands, start to read the owner’s manuals and installation instructions so that you can begin the next phase: wiring them together! Trust me, it’s much easier to bite off this step before you get started with the wiring and fusing. Most manufacturers offer excellent advice about how to do it and have consumer relations experts who are ready to guide you. But stay tuned for more about campervan electrics from us here at Off Path Travels as well!

Is there anything that’s still confusing you? Or do you have something to add? Leave a comment below to share your thoughts!

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