The Complete Guide to
RV Solar Panels, To Go

RV solar panels have taken boondocking to a whole new level. If you've been plagued by dead batteries in the past, solar panels are the answer - unless you camp in a cave! Investing in a solar panel charging system is one of the best things you can do for your RV.

In 2010 I became a full-time RVer and since then I've relied on solar power and nothing but solar power. All the power I need comes directly from the sun. I'm convinced it is the absolute best way to charge batteries.

In this solar power series I will talk about the advantages of going solar, help you select the best solar panels and charge controller, and give you tips on how to tilt your panels for maximum power output.

Solar panel tilted for optimal power output

Top 10 Reason to Go Solar

1. It's Free! Free energy from the sun is transformed into pure DC electricity. No costly fuel required.
2. Best For Your Batteries: The best way to charge your batteries is slowly and steadily with pure DC current, and that's exactly what RV solar panels do.
3. Silent: No noise, unlike generators or wind turbines.
4. Safe: No risk of carbon monoxide poisoning or fires as with a generator. The risk of electric shock is minimal due to the low levels of current produced.
5. Clean: No messy fuel or oil to deal with.
6. Better for the Environment: Does not pollute the air or release CO2 into the atmosphere when operating.
7. More Neighbor Friendly: Your neighbors (if any) will appreciate not having to breathe exhausts fumes or tolerate noise from a generator.
8. Fully Automatic: Flip the switch on the solar charge controller and that's it. Your batteries are charged while the sun shines and the unit shuts off when the sun goes down (so that current does not flow back out of your batteries and into the panels at night).
9. No Maintenance: Except for cleaning dust from the panels every now and then, nothing more needs to be done.
10. Sets You Free! No need to plug into shore power and you can go RV boondocking for as long as you like. Dead batteries are no longer a problem.

Selecting RV Solar Panels

The components of an RV solar power system are:

• RV Solar Panels
• Solar Charge Controller
• Deep Cycle Batteries
• Inverter

I will cover RV Solar Panels here and Solar Charge Controllers in this article. You will also need deep cycle batteries to store the energy produced from the RV solar panels, and an inverter to convert 12 volt DC power to 120 volt AC power for your AC appliances.

Here are the steps for selecting the right RV solar panels for your needs:

1. Calculate Your Daily Power Consumption
2. Determine RV Solar Panel Wattage
3. Check the Specs on RV Solar Panels

1. Calculate Your Daily Power Consumption

In order to select the right sized RV solar panels and decide how many you will need for your power requirements, first calculate your daily power consumption in amp-hours.

Tally up your DC devices first

Take the amp rating for each DC device in your RV and multiply this number by the hours it is used each day, as this table shows. This will give you the total amp-hours that device uses.

You can use the DC Current Usage Chart for your calculations, however the numbers are only approximate. For a more accurate total, you will need to check the amp rating on each device in your RV.

In our sample table above, we have a daily total of 17.6 DC amp-hours.

Next, add up your AC devices

You will do the same as you did for DC devices, however this time Watts will be calculated instead of Amps. So find the watt rating for each AC device in your RV. If you only have the amp rating for a device, take amps X 120 (for 120 volts) and this will give you the current draw in watts. Do Not include devices that will be powered by a generator, like an air conditioner for instance.

Click here to view an AC Current Usage Chart for common 120 volt AC devices.

In our sample table above, we have a daily total of 270 AC watt-hours.

Now you will need to convert your AC watt-hour total to amp-hours. To do this, divide the total watt-hours by 12 (for 12 volts). For our example, 270 divided by 12 = 22.5 amp-hours.

For your AC devices, you will be using an inverter. Since an inverter is not 100% efficient, there will be some wasted energy. You will need to multiply your AC amp-hours by 1.2 to account for this loss. For our example, 22.5 amp-hours x 1.2 = 27.0 amp-hours. We have a daily total of 27.0 AC amp-hours.

Total up your DC & AC amp-hours

For our example, we'll add our DC amp-hours (17.6) with our AC amp-hours (27.0) to get a daily total of 44.6 amp-hours.

Include Phantom Loads

You will also need to include the power consumption of devices that have phantom loads. These devices draw current continuously, even when off or on standby. They will need to be calculated like above, whether DC or AC and added to your total. These can include:

• Refrigerator (even when on LP mode it can draw 0.5 to 1.0 amp)
• TVs
• Stereos
• Microwave
• Propane and Carbon Monoxide Detectors
• Clocks
• Auto-ignition Pilot Lights

Many of these devices will draw current around the clock, and the power consumption can really add up. You can eliminate some of these phantom loads by installing on/off switches on the devices, or plugging them into a power strip which can be switched off.

Calculate Battery Bank Size

For our example, we will pretend we've eliminated all phantom loads (unlikely in real life) and our daily power consumption is 44.6 amp-hours, as calculated above.

It's best to avoid discharging your batteries by more than 25%. That means we will need to multiply our total amp-hours by 4 (44.6 amp-hours x 4 =  178.4 amp-hours). We will need a battery bank capacity of at least 178.4 amp-hours in our example. Two group 27 deep cycle batteries (providing 100 amp-hours each) would work well in this case.

2. Determine RV Solar Panel Wattage

We've calculated our daily power consumption, and know what size of battery bank we need. Now it's time to decide just what it's going to take to keep those batteries charged up and ready for action.

Since the sun doesn't always shine (even in Arizona!) you'll need to take into account your latitude and how often clouds appear. The further north you are, the less intense the sunshine will be (in the northern hemisphere). And cloudy days can cut your solar production in half.

• The Southwest sees plenty of sunshine. Therefore 1 watt of solar panel output for every 1 amp-hour of battery capacity is recommended. With 200 amp-hours of battery capacity, 200 watts of solar power should do the job.
• The Pacific Northwest sees many cloudy days and since Alaska is so far north, the sun is not very intense, even in summer. At least 1.5 watts of solar panel output for every 1 amp-hour of battery capacity is recommended. A 200 amp-hour battery bank should receive 300 watts of solar panel power.
• Parking in the shade will decrease solar output and several cloudy days in a row can hamper battery charging. Having a few more watts in your RV solar array can help out in times like these. You can never have too many solar panels.

Can't afford to purchase all the RV solar panels needed for your power requirements? Not a problem. It's very easy to add additional panels later. Just remember to leave enough room on your roof to grow your solar farm. It's also important to choose a solar charge controller with a peak power amp rating that will handle your future solar panel additions. You may need to utilize additional charging methods until you've completed your RV solar array.

3. Check the Specs on RV Solar Panels

Don't rush off to the store just yet! Check the specs, before you write the check. These are important specifications you should know before purchasing RV solar panels:

• Watt Rating: This is necessary for sizing your system as mentioned above.
   
• Peak Power (Amps): The maximum power in amps that the panel can produce in full sunlight. If the solar panel has a peak power rating of 5 amps and you plan on having a good 6 hours of sunlight per day, then you can expect 30 amp-hours of charging a day (5 x 6 = 30). When choosing a solar charge controller, you'll need to know the combined peak power rating of your solar array so that you can choose a controller with the correct amp rating (more on this in the Solar Charge Controller article).
   
• Peak Power (Volts): The maximum power in volts that the panel can produce in full sunlight. This is very important because as the solar panel heats up, it becomes less efficient. The output can drop as much as 2 volts and this can greatly affect the charging rate. Low light conditions will also reduce your charging rate. The higher the number here, the better the performance. 17 volts or higher is recommended.
   
• Tolerance: A 100 watt solar panel with a tolerance of 10% means that it may only produce 90 watts of power. The lower the percentage here, the better. 5% is good as the panel will come closer to its rated wattage.

Conclusion

I hope this article has "shed a little light" on the subject of RV solar panels. The age of solar power is upon us. More and more RVers are realizing the advantages of going solar. I wouldn't be surprised if a solar power system became standard on RVs of the future. Now go out and grab some RV solar panels, and may the sun be with you!

More on Solar Power

Learn how to choose a solar charge controller, tilt your solar panels for maximum power output, and put a small portable solar panel in your backpack. It's all here...

• Choosing a Solar Charge Controller
• Solar Panel Angle, Tips for Tilting Solar Panels
• Portable Solar Panels for Hiking, Backpacking, Biking, and Boating

References

• Woodall's RV Owner's Handbook by Gary Bunzer
• The Complete Book of Boondock RVing by Bill and Jan Moeller
• AM Solar