RV Solar Sizing: Tally Daily Watt Use, Then Add 20 Percent, Engadget Guidance Says

The publication notes that fully powering an RV with solar is possible, but it requires three additional components beyond the panels themselves: a battery bank to store energy after the sun goes down, an inverter to convert stored direct current into the alternating current the rig's systems use, and a charge controller to route power from the panels into the battery bank. Engadget reports that combining solar with non-solar generator power remains the more common approach among RV users, although an all-solar setup can work with that hardware in place.

Sizing those components depends on how many panels the rig carries. According to Engadget, an inverter should be rated at about 1.25 times the number of watts needed at any given moment. The article estimates that a 100W solar panel, once weather and sun exposure are accounted for, collects about 350W of power per day. Owners are advised to check how much power each device uses over the course of a day and add those figures together, starting with the label on each device. Where a label lists only volts and amps, multiplying the two yields watts.

The calculation covers more than the electronics kept inside the RV, which Engadget lists as including charging units, portable heaters, cooking equipment and GPS devices. The panels themselves also have to be factored in. No panel delivers the maximum power it advertises, the article says, particularly during periods of low sun exposure or while travelling through forested areas. Panel temperature matters as well: cooler conditions produce more efficient results, making bright, cold days the best case for output.

Engadget points to the 20 percent rule that most solar panel users follow, which holds that a setup should generate 20 percent more energy than the rig requires, providing a buffer for stretches when sunlight is scarce. A 400W panel, the article says, suits many of those purposes and satisfies the rule. The underlying assumption is that a panel will operate below its maximum output for the majority of the time, so owners need to plan for that shortfall rather than for peak conditions.

The article walks through the arithmetic an owner should complete before buying anything. Each device's hourly wattage is tallied, then multiplied by how long the device actually runs per day. A device rated at 1,500 watts per hour that is used for only ten minutes in a day consumes about 250 watts. Once that daily total is established, the recommended solar setup is one that can output that amount per day plus 20 percent more.

The guidance arrives as renewable energy takes on a larger role in daily life, a shift Engadget links to worsening climate change and to new consumer markets such as plug-in solar in the United Kingdom. For RV users, the appeal of solar lies in off-grid power without the noise of a typical generator.