Making sure your lighting is as efficient as possible takes on even more importance in off-grid systems due to expensive battery banks that should not be overdischarged and the winter double-whammy of more hours of darkness combined with a reduced solar resource.
For off-grid homes, the lighting focus will likely be more on efficiency than light quality, but you don’t have to compromise—much. As my old FLs and CFLs burn out or get dim at my off-grid home, I am slowly phasing in LED lamps. So far, I’m satisfied. The cost of LED lighting is still high, but not as high as the cost of a new battery bank or adding PV modules.
Because most modern inverters provide a nearly pure sine-wave output, FLs, CFLs, and LEDs or dimmers usually work well. However, modified wave inverters used in smaller or older off-grid installations can cause problems with these newer lighting technologies. Expect an efficiency loss of 10% to 20%—as with any appliance that has inductive or capacitive elements (ballasts, motors, computers, etc.)—and the possibility of flickering or audibly buzzing lamps.
In very small off-grid systems such as for cabins, RVs, tractor-trailers, and boats, DC lighting can make sense, though only with LED fixtures and lamps. (DC CFLs are available, but are expensive, difficult to find, and very sensitive to voltage drop in DC wiring, which shortens their life drastically.) A bonus with DC lighting is that because an inverter is not necessary, it is more efficient. The problems with premature LED burnout have been solved with the latest DC LED products, which use efficient power electronics to provide a constant voltage to the lamp no matter what the battery bank voltage, with built-in energy-saving dimming capability.
Although many modern off-grid homes use true sine wave inverters, allowing the same light choices as on-gridders, DC LEDs can offer improved lighting efficiency at a reasonable cost.