RV Solar Calculator
Two numbers decide your whole system: what you use in a day, and how much sun you actually get. Everything else is arithmetic. Put your daily watt-hours in, get back the panels and the battery bank that will carry you.
Live · Updates as you type Solar Sizing
Your system
Wh
W
Panels needed
3 × 200W
Array size
600 W
Battery bank (12V)
313 Ah
| Step | Value |
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Assumes 70% system efficiency (charge controller, wiring, heat, and panel derating) and 12V nominal batteries. A planning estimate, not a system design: your real sun hours, shade, panel angle, and temperature all move the answer. Get anything you intend to wire checked by a qualified installer.
Frequently Asked Questions
List everything you run, multiply each item's watts by the hours a day it actually runs, and add it up. A 12V compressor fridge is usually the biggest number and typically lands somewhere around 500 to 900 Wh a day depending on size and outside temperature. A laptop is roughly 50W while it charges. LED lights are almost nothing. The honest way to do it is to fit a battery monitor and read the real figure after a week; every estimate people make is low.
Not daylight hours. A peak sun hour is one hour of full-strength sun, and a day's worth of weaker sun gets converted into that equivalent. Arizona in June is around 6 to 7. The Pacific Northwest in December can be under 2. Size for the worst month you plan to camp in, not the annual average, or your system works in July and quits in November.
Because nothing in the chain is free. Between panel derating, heat, wiring losses, the charge controller, and the fact that panels almost never sit at the perfect angle, you lose roughly 30% of the number printed on the panel. This calculator assumes 70% efficiency, which is a normal real-world figure for a decent install. A rooftop array in the heat with no tilt does worse.
Because rated capacity is not usable capacity. Draining a lead acid or AGM battery below about 50% wrecks its life, so a 100Ah AGM realistically gives you 50Ah. Lithium is comfortable down to 20% or lower, so a 100Ah lithium gives you 80Ah or more. That is why lithium looks expensive per rated amp-hour and often is not per usable amp-hour. The catch is cold: lithium will not accept a charge below freezing without a heater or a low-temperature cutoff.
Only with a system far bigger than most people are picturing. An RV air conditioner pulls somewhere around 1,200 to 1,500W while running, so a few hours a day is several thousand watt-hours on its own, plus an inverter big enough for the startup surge. It is done, it needs a serious lithium bank and a lot of roof, and it is the single most expensive thing you can ask of an off-grid system. Shade and a good fan are much cheaper.