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Going solar is no longer just a fad, as campers and RVers will tell you it really makes a difference. But for a beginner the question is, how do you find out how many solar panels you will need? Figuring it out actually straightforward.
An RV requires at least one 150 watt solar panel to cover basic necessities. A 300 watt solar panel with a 100ah battery bank is the minimum for two people.
How to Calculate RV Power Requirements
If you have some experience with solar power and been on RVs for a while, making the transition to solar should pose no problems. If you have never used solar for your RV before, read on to find out the best way to calculate how much power you have to install.
There are two things to keep in mind regardless of the size of your RV:
The power your solar panels store in the battery: solar panels generate energy from the sun, but since the sun is out only for a limited number of hours, you have to store that energy in a battery for use later. A battery bank refers to a series of batteries linked together to store energy.
The amount of power you use, measured in amp hours (ah). The watts and amps in your system determines how much power you have to get. The more amp hours you consume, the higher the watts and ah capacity needed.
There are 2 ways to calculate solar power requirements.
Run an RV Power Usage Experiment
- Take your RV out and use it as you would on a regular day. If you haven’t already, set up a battery monitor. In this example we are using lead acid 200 amp hour batteries. Don’t turn on the generator.
- Keep an eye on the battery indicator and see how much you use up. Do not minimize your use of appliances and electronic devices. Just use them as you would daily. This way we’ll know how much solar power you really need. Do not let lead acid batteries drop below 50%. Letting the battery go under 50% will decrease its lifespan and make it unusable in the long run. Even other types of solar batteries should not b drained completely.
- Determine how many days it takes for you to drain the battery to the 50% level. If it takes 2 days to drop to 50%, it means you use 50 amp hours daily. Remember you must not let the battery level drop to 50%, so that 200 amp is really 100 amp. 100 amp use over 2 days means 50 amps per day.
Using the steps above you will get an idea of how many solar panels and battery capacity are required. If the battery level drops to 50% in less than a day, get a bigger capacity battery bank. Remember, your solar panels are only as good as the amount of energy that can be stored in the batteries, so a bigger bank means more energy accumulated.
Calculate Daily Power Use
Here you manually calculate how much power your appliances and devices consume. This can be useful for some, but it’s just a tedious process. You have to record how long you watch TV, how many watts it uses, and repeat for every electronic device / appliance you use.
This method is not only cumbersome but impractical, since we don’t watch the same number of hours of TV per day. The same applies to your laptop, hair dryer and so on.
You don’t use them the same way daily, so calculating will be difficult and inaccurate. Stick to the first method as it’s more precise. This is only useful if you want a ballpark figure and is still in the planning stage.
How Many Solar Panels Do I Need For My RV?
After you figure out how many amp hours you use, next is how many solar panels should you install?
It depends on how much power the solar panels generate. This table should give you an idea what solar panels are ideal based on your daily amp hour use. The brand names here are examples only. You can buy any brand as long as the watt output is in the appropriate range.
|Amp Hours||Solar Panel Power Required||Batteries Required|
|17.14 aH||50W Solar Flex Kit||1|
|26.42 aH||80W Portable Solar Kit||2|
|33.71 aH||100W Solar Flex Kit||2|
|40.14 aH||120W Portable Solar Kit||2|
|53 aH||170W Overlander Kit||2|
|67.42 aH||200W Solar Flex Kit||4|
|165 aH||500W Solar Flex Kit||4|
|158.85 aH||680W Solar All-Electric Kit||4-6|
|324 aH||1020W Solar All-Electric Kit||4-8|
Under perfect conditions, a 100 watt solar panel produces 100 watts, but perfect conditions rarely happen. Weather, time of season, cloud cover, sun intensity, battery storage capacity, solar panel quality all are factors.
Assume you use 50 amp hours a day. With the table above you’ll see that a 100 watt, 5.43 amp hour solar kit is ideal. Why? If there are six hours of sunlight your solar panel can use, that gives 32.5 amps. If there is more sunlight that’s even better.
Now pair the 100 watt solar panel with another 100W solar panel and you get 65 amp hours, more than enough for the 50 amp hours you use daily. With 200 watts there is plenty of reserve in case of emergency use. If you figure there is going to be plenty of cloudy days ahead, stock up on energy reserves. This is where that battery capacity comes into play.
This is just an example of how to calculate solar power requirements. For higher or lower amp hour use, look up the table and see which solar setup is the best match.
Tips for Saving RV Solar Power
You can save and reduce power usage by following these tips.
- Park you RV in shade. This means you don’t have to turn on the fan and helps cool down your rig.
- If it’s hot, use the awning to cool down.
- If it’s cold, keep warm with clothing and not just your heater.
- Don’t waste water while showering. This also applies when cleaning dishes.
- Use energy efficient appliances. If you have to replace older models, do so. You’re going to spend money now yes, but think of it as an investment for the future.
- Use LED whenever possible. Good news is LED lights are widely available.
- Unplug electrical devices and appliances when not in use. Unplug the laptop when you’re done. Remove the charger when your phone is ready for use. You get the picture.
- Not sure what battery capacity to use? Match your solar panel’s W output with the battery ah, i.e. 200 W solar panel and a 200 ah battery capacity.
- Buy from reputable manufacturers. This applies to solar panels, batteries, inverters, everything. Fixing a faulty component can be difficult especially if you’re new to solar power use.
Before you buy a portable solar panel kit, keep the following in mind. Even the most powerful solar system is only as effective as the amount of sunlight available. If there isn’t much sun you just won’t get a lot of energy. Second, make sure the battery corresponds well with the solar panel so energy is stored properly.
Small changes in your daily habits can save a lot of energy. Read during daytime so you don’t have to turn on the lights at night. If it is hot in the RV, don’t turn on the fan. Just go out, set up the awning and enjoy the fresh air. Even the best solar panels can have an 85% efficiency drop on cloudy days, so provide some allowance for your every day use. A 20% reserve is ideal.
And by the way it doesn’t make sense to fill your RV with solar panels so you can capture all that sunlight. For one thing, you won’t be able to store that energy unless you have a really large battery bank. Lots of solar panels and plenty of big battery banks will get expensive and become impractical.
Calculating how much solar power you will need isn’t as difficult as it seems. With careful planning you’ll be able to figure out the number, especially with the method provided above. Know how much you’ll need and finding the right number of portable solar panels won’t be an issue.