Off-grid solar on an RV is sold as a number of watts on the roof. What you actually need is a system sized backwards from what you run, how long you run it, and how much battery you can carry, and in Lake Havasu the heat changes two of those three. Here’s how to size it honestly, and what to look for on a used rig that already has it.
Start from the load, not the panels
Add up what you run off-grid on a typical day: refrigerator (if it’s a 12-volt compressor fridge, it’s the biggest draw), furnace fan, water pump, lights, phones and laptops, the inverter’s own overhead, and anything you plug into the inverter. The result, in amp-hours or watt-hours per day, is the number everything else is sized from, together with the biggest loads you’ll run at the same time.
The three pieces
Battery bank. It carries you through the night and the cloudy day. Lead-acid banks are typically run to only about half their rated capacity to protect their life, and heat kills lead-acid in two to three years here; lithium gives you most of its rated capacity, weighs less and tolerates heat better, but has its own charging-temperature limits that matter in a Havasu summer. Size the bank to cover at least a day of your load without sun.
Panels. Roof panels are limited by roof space and shade; portable panels can chase the sun. Rate them against your daily load and the real number of sun hours, not the label. Dust is a Havasu factor: a dirty panel in the desert can lose a meaningful share of its output, so plan to wipe them.
The charge controller and inverter. The controller turns panel output into battery charge; MPPT controllers generally harvest more from the panels than PWM controllers, and some MPPT controllers throttle above 120 degrees, which the inside of a Havasu basement compartment can reach. The inverter turns battery power into household power for the things that need it; size it to the loads you’ll run at the same time, including motor start-up surges, and check that its output type suits the electronics you’ll plug in.
What solar won’t do
Air conditioning. A rooftop A/C unit draws more than most RV solar systems can supply for more than a short time, which is why boondockers in Havasu either run a generator in the afternoon or aren’t here in the summer. Solar keeps the refrigerator cold, the batteries charged and the lights on; it doesn’t make July comfortable.
Buying a used rig with solar already on it
- Ask for the component list: panel wattage, controller type, battery chemistry and age, inverter rating. “Has solar” means nothing without it.
- Check the battery date and condition; batteries are commonly the first component to need replacement and among the most expensive.
- Look at the wiring and the roof penetrations: every hole a solar install puts in the roof is a place a leak can start, so follow the specific manufacturer’s inspection schedule and approved sealant requirements and have damaged or separating seals addressed promptly.
- Test it at midday: watch the controller’s charge rate and the battery monitor with the fridge running.
- Factory solar prep (the wiring and port) is not a solar system; it’s a place to plug one in.
We can tell you what’s on a unit and what we found when we walked it; we don’t promise that every system works. An independent inspection, paid by the buyer, is always welcome, and a mobile RV tech in Havasu knows what the heat does to these systems.
Next step
See the RVs in stock, or read the boondocking rules every RV owner needs to know. Our service shop handles batteries and electrical. Call (928) 453-8833 or text (928) 732-2281.
