Recently bought a house in the Seattle area, built about 1980. At the time
the house was built, there was no gas in the area. The house has a heat
pump, which is nearing the end of its life. Natural gas is now available in
the area. I'm wondering if I should go with another heat pump, or natural
gas. Since about 80% of the electricity here is hydro, it's relatively
cheap, about $.08/KWH. I don't know what the price of the gas is per cu',
but I could find out. Is there a way I could get a rough estimate of how
much natural gas I would consume to heat the house, based on the electricity
used for this purpose? There are a lot of confounding factors, the relative
efficiency of the 2 units (old heat pump vs new nat'l gas furnace), the fact
that I also use electric to heat water, etc. (can probably find some rough
figure for factoring this out) the relative costs of each type of
replacement (I would add AC to the gas furnace, so I'm guessing the gas/AC
unit would cost more to buy initially than the heat pump, especially if I
have to shell out for the gas line to be run). Coming from the midwest,
electric heat was always seen as significatly more costly than natural gas,
but I don't know if this is still the case just in general, and particularly
if it would be true given this region's relatively low electric rates. Any
helpful comments appreciated.

TIA,

Dan