I assume you mean general room lighting. For that I'd use a 4Sevens MiNi AA tailstanding for ceiling bounce. (@40hrs. runtime on low). Or a Maratac AA/AAA, PALlight, etc. Most LED lights with a low setting would run for days, especially if used only at night. There's also 12hr. glow sticks. And lastly I'd go with candle lanterns due to safety concerns. For long term outtage I've got a small 700ma USB solar panel for charging Li-ion and NiMH and even a Dietz Air Pilot. But thats really for outside use.