Add up the watt-hours you use per day, then divide by the peak sun hours where you camp, and add a margin for losses and cloudy days to get panel watts. Size the battery bank to cover at least a day of use, choose an MPPT charge controller rated for your panel array, and size the inverter to the largest AC load you will run at once.
Solar works when the system is sized for how you live, not the biggest panel that fits.
Step 1: daily use
| Load | Watts | Hours per day | Watt-hours |
|---|---|---|---|
| Example: 12 V fridge | Average draw | 24 | Watts x 24 |
| Example: lights | Total watts | 4 | Watts x 4 |
| Example: laptop | Charger watts | 3 | Watts x 3 |
Use the wattage on each device’s label or spec sheet, and add every load.
Step 2: panel watts
Panel watts ≈ daily watt-hours ÷ peak sun hours, plus a margin for wiring, heat and panel angle losses. Winter and northern trips have fewer sun hours.
Step 3: battery and controller
- Battery bank: at least one day of use. See lithium vs AGM.
- Charge controller: MPPT, rated above your array’s current and voltage.
- Inverter: sized to the largest AC load you run at once.
Related: all off-grid power.
Common questions
How many solar panels do I need for an RV?
It depends on daily use and sunlight. Estimate watt-hours per day, divide by sun hours, then add a margin for losses.
MPPT or PWM charge controller?
MPPT controllers harvest more energy, especially in cold weather and with higher-voltage arrays. PWM controllers are cheaper and simpler.
Can solar run an RV air conditioner?
Running a roof air conditioner on solar alone takes a very large panel array and battery bank. Most RVers use shore power or a generator for air conditioning.