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About five years ago, I swapped my gas domestic hot water to a heat pump unit and my electric bill actually went down. Just being able to patch and insulate the roof exhaust from the gas unit saved more in spaced conditioning than the added (but minimal) electric load from the new heat pump itself.

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I take it that was an indoor gas water heater? Which used your indoor cold air? So it's analogous to a decorative fireplace losing good air up the chimney.

Pretty much all gas water heaters are indoors in the US. I was worried about the electricity consumption of our heat pump water heater, but it's actually minimal.

The coefficient of power is like 5 or something, and, since it's a bit more expensive than a contractor-grade water heater, I think the manufacturer also spent an extra $10 on better internal insulation or something. It uses much less than 1/5th the energy I'd expected, even with the "turn yourself down at night" feature disabled.

Majority of gas water heaters I have seen in Southern California have been exterior in a shed, or in a garage, so not pulling good air from the living space. I can't speak to Northern California.

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