If the concern is gaurenteeing that power is always available, the answer is a backup generator. It won't consume fossil fuels unless it's actively in use (very

If the concern is gaurenteeing that power is always available, the answer is a backup generator. It won't consume fossil fuels unless it's actively in use (very rarely). The carbon taken out of the atmosphere by having an efficient house with solar and grid connection during the rest of the year will more than offset the generator. I contend that the unsexy combination of solar, a bidirectional grid connection, and an emergency diesel generator is more efficient and environmentally friendly than any existing system involving hydrogen or batteries.