Use this RV solar calculator to find out how many solar panels your RV needs. Enter your daily power use in watt-hours, pick your sun hours and panel size, and see the watts of solar and the panel count you need for boondocking.
How to Use the Calculator
Type your daily power use in watt-hours, then pick your sun hours and panel size. The result shows the watts of solar to buy, the number of panels, the minimum watts you need, and what that system makes in a day.
How the RV Solar Calculation Works
The calculator divides your daily watt-hours by what one watt of panel makes in a day, which is your sun hours times 0.7. Heat, wiring, and charging losses keep panels below their rated power. The answer is the watts of solar you need, rounded up to whole panels.
At the default of 1,500 Wh a day and four sun hours, one watt makes 2.8 Wh a day. You need at least 536 W, which is six 100 W panels, and that system makes about 1,680 Wh a day, a comfortable margin for cloudy spells.
Find Your Daily Power Use
A watt-hour (Wh) is one watt of power used for one hour. A 10 W light on for 4 hours uses 40 Wh, and a 60 W laptop for 4 hours uses 240 Wh. Add up everything you run in a day, using the watts printed on each device’s label.
The most accurate way is to camp a few days on your battery and watch your battery monitor. If it shows amp-hours, multiply by 12 to get watt-hours on a 12-volt system.
Pick Your Sun Hours
SolarReviews defines a peak sun hour as one hour of sun at 1,000 watts per square meter. That measures energy, so a long day can give fewer peak sun hours than its length suggests. It calls 4 or more a good threshold for useful solar production.
Four is the default here. Pick 3 for cloudy or winter days, 5 for sunny summer days, and 6 for the Southwest in summer. Phoenix gets about 7.5 peak sun hours a day on average, according to SolarReviews, and Chicago about 4.
What Different Panel Sizes Make
Here is what a system makes in one day with four sun hours and the 70 percent factor. RV electrical expert Mike Sokol told RV Travel readers to expect 300 to 400 Wh a day from each 100 W, so these figures leave you a small cushion.
- 100 W of panels: about 280 Wh a day
- 200 W of panels: about 560 Wh a day
- 400 W of panels: about 1,120 Wh a day
- 600 W of panels: about 1,680 Wh a day
How Many Solar Panels to Charge a 100Ah Battery?
A 12-volt 100Ah lithium battery holds about 1,200 Wh. Mike Sokol notes that a flooded or AGM battery should only be discharged to 50 percent, which leaves about 600 Wh. With four sun hours, one 100 W panel makes about 280 Wh a day, so a full recharge from empty takes four to five days, or longer on a cloudy trip.
To refill it in one day, divide 1,200 by 2.8 and you get about 430 W of panels. For a lead-acid battery used to half, the number is about 215 W.
Can Solar Run an RV Air Conditioner?
Yes, but it takes a big system. CamperSmarts says a 13,500 BTU rooftop unit surges at about 2,750 W and runs near 1,250 W. Its sizing example calls for seven 400 W panels and a large battery bank, and it estimates the cost at over $10,000.
CamperSmarts concludes that this setup suits full-time dry campers in sunny places. Most RVers size solar for lights, a fridge, fans, and electronics, and use shore power or a generator for the A/C. That keeps the system smaller and far cheaper.
Panels Are Only Part of the System
Panels do not power anything on their own. You also need a charge controller, a battery bank, and wiring and fuses sized for the current. Our battery runtime calculator shows how long a battery lasts, and our generator size calculator helps with backup power.
Count how many panels fit around your vents, A/C, and antennas. Panels add height too, so measure again with our height clearance calculator.
Your Next Step
Write down your daily watt-hours, run them through the calculator at 3 and 5 sun hours as well as 4, and compare the three panel counts. The gap shows how much a cloudy trip changes your plan, and it tells you whether to add a cushion.