Thanks for the additional info. In my original analysis, I had used
$0.09246 as PGE's standard domestic rate, but if this rate has since
changed and the schedule shown on PGE's website is out-of-date, please
let me know.
Again, an air-source heat pump with a HSPF of 8.5 will provide, on
average, 2.5 kWh of heat for every kWh consumed, so your effective
cost of electric heat is 3.7 cents per kWh(e). At $1.22449 per therm
and assuming an AFUE of 90 per cent, your cost per kWh of natural gas
heat works out to be 4.64 cents. In this case, natural gas must fall
below $0.98/therm before it breaks even.
For argument sake, we'll assume a typical new home in your climate
requires 50 million BTUs/year for space heating purposes. At current
rates, if it were heated with electric baseboard units, the cost would
be just under $1,355.00, whereas that same home heated with an
air-source heat pump would come in at $542.00. Equipped with a high
efficiency natural gas furnace (90% AFUE) and at $1.22449 per therm, a
homeowner could expect to pay something in the order of $680.00/year.
Natural gas is a terrific fuel but we're quickly running out of it and
over the long term, not withstanding any temporary price fluctuations,
it's going to get increasingly more expensive. For anyone building a
new home or replacing their current heating system, I hope you
consider either an air or ground source heat pump as one more option.