Free RV tool
RV Solar Calculator
How many solar panels and how much battery does your recreational vehicle (RV) need? Tick what you use, set how long each runs, and we’ll size your panels, battery, charge controller and inverter, and show how we worked it out.
1. What do you run each day?
Watts are on the label or charger of each item. These are typical numbers; change them to match yours. “12V” (12-volt) items run straight off your RV battery. “110V” (110-volt) items plug into a wall socket and need an inverter when you’re off-grid.
2. Your sunshine and battery
Plan for the cloudiest season you camp in, not the sunniest.
LiFePO4 (lithium iron phosphate) is the usual RV lithium battery. AGM (absorbent glass mat) is a sealed lead-acid battery.
3. Your roof (optional)
Measure the longest clear stretch of roof, away from vents, the air conditioner, the antenna and anything that casts shade. Stay safe: measure from a ladder, or use the RV’s brochure. Don’t walk on a roof unless the maker says it is walkable.
☀️ Your RV uses about 1,134 watt-hours (Wh) a day
Here is a solar setup sized for that, with 2 days of battery backup.
How we worked it out
- 12-volt items: 720 Wh a day. 110-volt items: 414 Wh a day, including about 15% lost in the inverter.
- Panels: 1,134 Wh ÷ 4.5 sun hours ÷ 0.75 (panels rarely make their full label rating because of heat, angle and wiring), rounded up to whole 100-watt panels.
- Battery: 1,134 Wh × 2 days ÷ 80% usable (lithium handles deep use well) ÷ 12 volts.
- Charge controller: panel watts ÷ 12 volts, plus 25% headroom.
- Inverter: your biggest 110-volt item plus 25%. Running two big items at once needs a bigger one.
Before you buy
- Check your roof space. A 100-watt panel is about 3.5 to 4 feet long and under 2 feet wide. Leave room around vents, the air conditioner and anything that casts shade.
- Air conditioners are a different league. Running a rooftop air conditioner on battery takes a very large battery bank and solar array. Most RVers use a generator or shore power (a campground hookup) for air conditioning.
- Get the wiring right. Use the right wire size and fuses. If you are not sure, have a qualified RV technician or electrician install or check it.
⭐ Solar Planner Pro is coming
We’re building a Pro version for RV owners and shoppers:
- Save your RV's setup and compare upgrades side by side
- A shopping list with wire sizes and fuses for your system
- A printable one-page solar plan to take to an installer
Planned launch price: $19.99, one time (no subscription). Join the list and we’ll email you when it’s ready, with a launch discount.
Help us make this better
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Words we use
- RV (recreational vehicle)
- A camper or motorhome you live in on the road.
- W (watts)
- How much power something uses while it runs. It is usually printed on the label or charger.
- Wh (watt-hours)
- Power used over time. A 60-watt TV on for 3 hours uses 180 watt-hours.
- Ah (amp-hours)
- How much energy a battery holds. At 12 volts, 100 Ah is about 1,200 watt-hours.
- 12V (12-volt)
- Items that run straight off your RV's battery, such as lights, the water pump and vent fans.
- 110V (110-volt)
- Items that plug into a normal wall socket. Off-grid, they need an inverter.
- Inverter
- A box that turns 12-volt battery power into 110-volt wall-socket power. Pure sine wave inverters are safest for electronics.
- Charge controller
- A box between the solar panels and the battery that charges the battery safely.
- MPPT (Maximum Power Point Tracking)
- A type of charge controller that gets more power out of your panels than the cheaper PWM (Pulse Width Modulation) type.
- Peak sun hours
- How many hours a day of full-strength sun your panels get. It changes with season, place and shade.
- LiFePO4 (lithium iron phosphate)
- The usual lithium battery for RVs. Lighter, lasts longer, and you can use most of its capacity.
- AGM (absorbent glass mat)
- A sealed lead-acid battery. Cheaper up front, but it lasts longest if you use only about half its capacity.
- LED (light-emitting diode)
- Low-power lights used in most newer RVs.
- CPAP (continuous positive airway pressure)
- A machine that helps with breathing during sleep. A heated humidifier makes it use much more power.
This calculator gives estimates for planning, not an installation design. Real results depend on your location, weather, panel angle, shade and equipment. Electrical work can cause fire or injury; follow each maker’s instructions and local codes. More help: our free RV guides.