Free calculator
RV Solar and Battery Calculator: How Much Do I Need?
Tick what you run and adjust the watts and hours. The calculator adds up your daily energy use and sizes the battery bank, solar array and inverter to match.
Your system
- Daily energy use–
- Battery bank–
- Solar array–
- Inverter–
Enable JavaScript to use the calculator, or use the formula and table below.
How the calculation works
- Daily energyFor each device: watts × hours per day. Devices on the inverter are divided by about 0.85 for inverter losses.
- Battery bankDaily watt-hours × days without sun ÷ 12.8V ÷ usable share (about 0.9 for lithium, 0.5 for AGM).
- Solar arrayDaily watt-hours ÷ (sun hours × about 0.75 for heat, angle, wiring and charge-controller losses).
- InverterThe largest 120V appliance you run at once × about 1.25 for headroom, rounded up to a common size.
Quick reference: typical RV setups
Two days of battery and spring/fall sun (about 4.5 hours), lithium battery.
| Usage profile | Daily use | Battery | Solar |
|---|---|---|---|
| Weekend camper: lights, fridge, pump, phones | 700 Wh | 120 Ah lithium | 200 W |
| Comfortable off-grid: adds laptop, TV, fans | 1,500 Wh | 260 Ah lithium | 450 W |
| Full-time / remote work: adds coffee, microwave, CPAP | 3,000 Wh | 520 Ah lithium | 900 W |
Before you buy panels
- Measure roof space first. A rigid 200W panel is roughly 5.5 by 2.5 feet; vents, the AC and the antenna limit how many fit.
- Winter changes everything. With 3 hours of sun you need about 50% more solar than in summer; a DC-DC charger fills the gap while driving.
- Cut the big loads first. A microwave or coffee maker can use more energy in 15 minutes than LED lights use all day.
More in the RV solar guide, RV batteries guide and best RV solar panels.
Frequently asked questions
How much solar do I need for my RV?
Add up your daily energy use in watt-hours, then divide by your peak sun hours and about 0.75 for system losses. A typical weekend setup using about 700Wh a day needs roughly 200W of solar in spring or fall; a full-time setup using 3,000Wh needs closer to 900W.
How big a battery do I need for RV boondocking?
Daily watt-hours times the number of days you want to cover without sun, divided by 12.8V and the usable share of the battery (about 0.9 for lithium, 0.5 for AGM). Two days of a 1,500Wh load needs roughly 260Ah of lithium.
Do I need an inverter for RV solar?
Only for 120V appliances such as a laptop charger, TV, coffee maker or microwave. Size it to the largest appliance you run at once with some headroom; high-wattage appliances like microwaves and coffee makers need a 2,000W-class inverter and drain a battery quickly.
Can RV solar run the air conditioner?
Not practically on most RVs. A roof AC uses well over 1,000W while running; even a few hours a day needs a very large lithium bank and more solar than most roofs can hold. Use shore power or a generator for AC.
Estimates only. Real output depends on panel angle, shading, temperature, wiring and equipment. Have high-current wiring installed to code.