How Much Solar Power Do I Need? How to Size RV Solar System?

If this is the first time you have decided to upgrade your RV with solar panel power, search no more because you have come to the right place. Also, by this time, you must have already known how solar panels can be a practical investment in the long run. They take the hassle out of drydocking, replace the need for the noisy AC generator, and do away with hookup cable clutters. What makes them an even better investment decision? Solar panel prices have been in decline for the past decade!

With that being said, solar for RV comes in all shapes and sizes. And to decide which one and how many are required for your trailer, you need to do a few calculations. It’s straightforward, however.

How much solar power do I need for my RV? The principle is that you first determine the actual energy usage of your RV. You then plug this number in an RV solar panel size calculator to get the battery banks, the solar panel number you need, as well as your solar charge controller.

Considering these pieces of information alongside your RV specs, you can get an idea how your van’s setup would be like. Sounds a little overwhelming, no? Don’t worry. Read on, and this article will teach you everything, piece by piece.

Determining Solar Power Demands

This step is of prime importance because, for starters, it answers the question: how much solar do I need for my van? Secondly, it provides the basis to make calculations of our 50 amp RV solar system later on.

Basically, the choosing of a solar system boils down to supply versus demand. The electricity demand of your RV can be calculated in one of two ways.

#1. Monitor Your RV Consumption

This method provides the most accurate result of electricity load, both the battery power AC power, because you will record the changes in the battery while using your trailer as usual.

And this is done using a device called a battery monitor unit, which technically is a component of the solar system. This measuring device is installed on the negative line of the RV electrical system and has a digital readout that calculates the power flowing into and out of the battery, recorded as Amp-hours.

Once the battery monitoring system is installed, have your RV fully charged up and use your van as you normally would. When your van has 50% power left (for lead-acid batteries) or 20% (for lithium batteries), note how long you have run and how many Amp-hours have been used.

You can then derive the power demand with these two figures. Find the Watt-hours by multiplying your Amp-hours with the nominal voltage of your battery system: 12.6V for lead acid and 13V for lithium.

For example, if your RV has a lead-acid battery that uses 150 Amp-hours in 12 hours, then the Watt in 12 hours should be 150 Amp-hours x 12.6 Volt = 1890. Multiply this by two, and we get the wattage demand for 24 hours of 3780.

#2. Pen and Paper Method

Jot down or create a spreadsheet of every appliance on your trailer that is going to use solar power, from your coffee maker to the air conditioner. List all the wattage of each item together with the number of hours it will be used. The information about wattage can be found on the appliance’s label.

Note that Watt equals Volt times Amp, so if a computer charger says 24V and 4.25A, multiply these numbers to get the wattage of 102.

This method will be tedious because you will have to keep track of each appliance’s wattage and add it to get the final result. Moreover, it’s less preferred than the first method because the final figure is just an estimate. Several environmental factors, such as temperatures, make the appliances work more or less than their standard parameters.

Determining Solar Power Supply

Now that you know the energy load you must supply against, we move on to answer ‘how many solar panels do I need for my RV?’. Calculating this value requires factoring in multiple variables.

The location, season, weather, temperature, etc., all affect how much power a solar panel can generate in a day. Therefore, it’s easier for us to use an automated calculator, such as that of a late store.

This tool isn’t designed specifically for RVers. Still, it makes precise calculations for solar panels using sun exposure data all over the U.S. You just have to plug in the required variables and which state you’re currently in (or the place where you will be camping). It will tell you the ideal solar power needed in terms of total wattage.

For example, if we plug in the 3780 watt-hours per day that we got earlier and we are in Tampa, Florida, we should supply a total of 1117 Watts.

Determining the Solar Panel Setup

So, I got how much electricity my van uses in a day and how much solar power should I need for my RV, but how many watt solar panels do I need for my RV? The answer to this depends on how many panels can be fitted on your RV, but the general rule is that every trailer should require a setup of two panels at a minimum.

One common misconception is that a panel needs to be capable of at least 500 or 600 watts to be worth it. You should get even a 900-watts one to be safe.

Realistically though, you only need as many watts as your usage warrants and as many panels as your batteries can store. Going overboard will result in economic inefficiency and wastage.

My personal suggestion here is to invest in better battery capacity first. You can always add more to your solar array later if you need more power in your battery bank.

Here are a couple of setups for our example:

• Three panels of 400w each
• Eight panels of 150w each

Conclusion

How much solar power do I need for my RV? The way you use your RV, how long you will run it, and how many appliances are on board all influence the total power usage that is required by your van.

You can determine how much this figure really is with the use of a battery meter while doing a test drive or camping test. The Amp-hours it reads during that time will be the indicator of your RV demands. You can estimate a ballpark figure by adding up the usage of each item inside, but this is inferior.

Plug the resulting wattage into the late store calculator, choose where you are currently or intended to go, and you will get how many watts your panels should provide. Taking into account how many panels can be fitted to the roof of your trailer and how much power your battery bank can store, you will arrive at the number of panels and watts per panel needed.

Should there be any questions or suggestions, please reach out to me in the comment section below. I would be glad to hear your thoughts and provide further explanation as needed. And if there are any RV users you know that also happen to set up a solar panel system in the future; please share this article with them. We’re all part of this adventurous community!