RV, off-grid and 12V systems

How Many Miles a Day Can Solar Panels on a Car Add?

Published · By the SolarPanelX editors · Prices and specs as of that date, from the pages under Sources

Summary

Toyota says the 185 W solar roof on its latest Prius plug-in hybrid adds up to 8.7 km, about 5.4 miles, of electric range a day, based on annual sunlight in Nagoya, Japan. The U.S. Department of Energy says today's electric cars use 25 to 40 kWh to drive 100 miles. A car roof adds a few miles a day at most, a very different job from keeping a 12 V battery topped up.

What a solar roof adds

In its June 2023 release, Toyota Motor Europe said the optional solar roof on the new Prius Plug-in Hybrid produces 185 W, up from 179 W. Earlier versions stored solar energy in a separate battery. The new roof charges the plug-in hybrid battery directly and can fill it if the car stays parked outside for just over a week.

Aptera, a three-wheeled EV still in development, says roughly 700 W of built-in solar cells can power up to 40 miles of driving a day. Its site adds that the vehicle is in testing and validation and specifications may change.

Against a day of driving

At the DOE's 25 to 40 kWh per 100 miles, a driver covering 30 miles a day uses 7.5 to 12 kWh. The Prius's 5.4 miles covers under a fifth of that 30-mile day.

VehicleSolar roofMaker's daily figure
Toyota Prius Plug-in Hybrid (Europe)185 Wup to 8.7 km (Nagoya sunlight)
Aptera (in development)about 700 Wup to 40 miles

Small panels for a parked car's 12 V battery

Maintaining the 12 V battery in a parked car takes far fewer watts. Battery Tender's 5 W solar maintainer has a built-in charge controller that switches to float mode once the battery is full, connects with alligator clips or a ring terminal, and mounts on the dashboard or windshield with suction cups. The 17 W model comes with a separate solar charge controller and a 6 ft quick-disconnect extension cable.

Shopping for one? Browse RV and off-grid solar panels →

Sources

  1. Toyota Motor Europe — All-new Toyota Prius Plug-in Hybrid (June 30, 2023)
  2. Aptera Motors
  3. U.S. Department of Energy, Alternative Fuels Data Center (electricity benefits page)
  4. Battery Tender — 12V 5W Solar Battery Charger & Maintainer
  5. Battery Tender — 12V 17 Watt Mountable Solar Battery Charger

We have not tested these products. Specs, prices, stock and terms are as published on these pages on the date above and can change; check the manufacturer or retailer before you buy.

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