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RV Solar Panel Sizing Calculator

Find out how many watts of solar panels you need for your RV based on your daily energy use, location, and battery system.

Inputs

A modest RV: 1000-2000 Wh. Heavy users (residential fridge, induction): 3000-5000 Wh.
SW deserts: 5-6. Northeast: 3-4. Pacific NW winter: 2.
Charge controller, wiring, panel angle losses.
LiFePO4: 95-98%. Lead-acid: 80-85%.
Common sizes: 100, 175, 200, 300, 400.

How RV solar sizing actually works

A solar panel rated at 200 watts will not produce 200 watts × 24 hours. It produces something close to its rated wattage only when the sun is high and the sky is clear, which most locations average between 3 and 6 hours per day. Multiply rated watts by those peak sun hours and you get a daily energy figure in watt-hours.

From there, real systems lose energy in three places: the charge controller (a good MPPT loses about 5%), the wiring and panel angle (another 10-15% in typical RV mounts), and the battery itself when you charge and later discharge it (5-20% depending on chemistry).

The calculator above bakes those losses in. The result is the array size that should reliably cover your daily use on a typical day. For boondocking peace of mind, oversize by 20-30% to handle cloudy days and shorter winter sun.

What "peak sun hours" really means

Peak sun hours (PSH) is a normalized way to express how much usable solar energy a location gets. One peak sun hour equals 1000 watts of irradiance per square meter for one hour. NREL maintains free PSH maps for every U.S. ZIP code — search "NREL PVWatts" and plug in your travel destination.

Tilted vs flat panels

Roof-mounted RV panels usually sit flat. Flat panels lose about 15% versus optimally-tilted ones in the summer, and 30-40% in winter when the sun is low. If you'll be stationary in winter, tilt mounts pay for themselves quickly.

Frequently Asked Questions

How much solar do I need for a typical RV?
Most weekend RVers do well with 200-400 watts. Full-time boondockers running a 12V fridge, lights, water pump, and electronics typically need 600-800 watts. Heavy users with a residential fridge, induction cooking, or air conditioning will need 1000+ watts plus a large lithium bank to store excess.
Will solar run my RV air conditioner?
Yes, but it's a serious system. A 13.5K BTU AC pulls about 1500 running watts. To run it for 4 hours a day off solar alone, you typically need 1500-2000 watts of panels paired with a 5-8 kWh lithium bank and a 3000W+ inverter. Most people run AC off shore power or generator and use solar for everything else.
Should I buy more panels or a bigger battery?
It depends on whether you're energy-limited or power-limited. If your batteries are full by 1pm and you still have sun left, you need more battery. If your batteries don't reach 100% by sunset on a clear day, you need more solar.
Do I need a charge controller?
Yes, always. A charge controller protects your batteries from being overcharged. PWM controllers are cheap (~$30) and fine for small systems where the panel voltage matches the battery (12V). MPPT controllers cost more but harvest 15-30% more energy and let you wire panels in series for thinner cabling. For anything over 200W of solar, MPPT is worth it.

Related Calculators

Battery Bank SizerRight-size your house batteries.Generator SizerRight wattage for your appliance load.Propane EstimatorDays per tank for your usage.

Want to understand the why behind these numbers? Read Boondocking Power Basics — the basics of watts, amps, and amp-hours.

Want to understand the why behind these numbers? Read Solar vs. Generator — when solar makes more sense than a generator.

About our math & sources

Every default and formula in this calculator is grounded in published manufacturer specs, industry standards, or peer-reviewed measurement. Where we make assumptions, we tell you what they are so you can adjust.

  • Peak sun hours. Geographic averages from NREL's PVWatts dataset (free, public). Search 'NREL PVWatts' for your specific ZIP code.
  • System efficiency 75% default. Combined losses: MPPT charge controller (~5%), wiring/temperature/angle (10–15%), real-world soiling (~5%). Quality installations can hit 80–85%; entry-level systems often run 65–70%.
  • Battery round-trip efficiency. LiFePO4: 95–98% (manufacturer spec sheets). Lead-acid: 80–85%, dropping with age. Both figures align with industry standards used by Victron, Renogy, and academic literature.
  • 25% safety margin. Standard practice for off-grid system design — accounts for cloudy days, panel degradation over time (~0.5%/year), and unexpected loads.
Disclaimer. This calculator provides estimates only. Real-world results depend on equipment efficiency, environmental conditions, and installation quality. Always verify against your equipment's spec sheets and consult a licensed installer for safety-critical decisions.