Our local gas company used to charge about 40% over the cost of the gas itself per therm. Now they charge 2 to 3 times the cost of the gas per therm.With a tank or a tankless, the operational cost of natural gas will beat electric resistance heating pretty much every time. Operational cost of heat pump water heaters compared to natural gas apparently can go either way, depending on the gas and electricity prices in your location. The cost to get the heat pump system installed is much higher, though. Seems like in most cases it would only be worthwhile if the heat pump is one of the complete systems, which replaces the WH, furnace and A/C, although the chances of needing all 3 at the same times seems fairly unlikely.