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RV Solar Power RoundUP Calculator

Solar Power Calculator for RVs and Boondockers

Use this handy calculator to estimate PV Wattage needs for your off grid RV activities and don't worry about electrical hook-ups.

The Amps listed below are estimates for typical electronic gear and appliances. You may alter the amp number to suit your actual appliances and equipment. Then, enter the number of hours, or fraction thereof as a decimal, that you estimate using those items during a typical day out on the water. Scroll down to "calculate" your estimated solar panel watt requirements.

The default below is set to 5 hours of direct peak sunlight per day, and you may also edit this data field as needed. You may get more or less direct sunlight, depending on your geographic location. 

RV Panel Size Calculator

Appliance Amps (at 12VDC) Daily Use (hrs/day)
12 Volt Appliances
12 Volt Stereo
Water Pump
Automatic Fan
10 Watt Light
15 Watt Light
Propane Alarm
120 Volt Appliance Using DC-to-AC Inverter
Small TV 9"
DVD Player
Anchor Light
Coffee Maker
Vent & range hood fan
Blow Dryer
Curling Iron
Medium Fridge
Total AmpHours per Day: 0


AmpHours used per day


Hours of Direct Sunlight per day
Minimum Watts Required


Recommended Panel Size (add 20%)



To identify the number of peak sun hours you can expect, determine the solar irradiance figure (kWh/m2/day) for your geographic location by using the interactive photovoltaic map provided by National Renewable Energy Laboratory (NREL), US Department of Energy. This will give you specific peak hours for a given month in your geographic location. Or, if annual average peak sun hours is sufficient for your estimates, review the NREL national photovaltaic map.

Now, cross-check your panel size estimate from the calculator vis-a-vie your marine on-board battery equipment. Calculate how many total watts of energy per day that you can get from your panels. Multiple your solar irradiance figure (kWh/m2/day) by 75% to account for inefficiencies during the charge process, and then multiply that figure by the total wattage of your solar panel.

Let’s look at one example with 180W of solar power in Miami, FL.

5.3kWh/m2/day x .75 x 180W = 715.5W 

In this case, from your 180W panels, you can expect to realize approximately 715.5 watts per day of solar power to charge your on-board batteries, and/or run other equipment directly from solar during the day.

As an aside, LearningDirect provides a clear and simple YouTube video on the issue of calculating peak sun hours.