For what it's worth, I am preparing to move into a rental house from an apartment building. The power is out, but the gas is still on. I cannot light the stove or turn on the furnace, but my hot water heater's pilot is still lit. We were inside the other day assembling some chairs and moving some boxes in - it was pretty cold inside, so I filled the sinks and bathtub with the hottest water we could make and it did make a noticeable difference.