On Sat, 05 Jan 2008 08:51:41 -0800, jJim McLaughlin
wrote:

[...]
Gut rule of thumb here in Portland, Oregon, where we are generally
without the benefit of heap BPA hydro is that gas in a 90% or 95%
efficient furnace is cheaper, by a long margin, than an electric ea pump with supplmental
resistance heat....

Hi Jim,

It might be helpful if we take a closer look at the numbers. The
trailing block rate for residential customers who opt for PGE's
standard domestic service pay $0.09246 per kWh ($0.07471 per kWh for
the first 250 kWh/month), so a heat pump with a HSPF of 8.5 (Zone IV)
would provide heat at an effective cost of just 3.7 cents per kWh(e).

For those not be familiar with the term, HSPF or Heating Seasonal
Performance Factor is defined as "the total space heating required
during the space heating season, expressed in Btu’s, divided by the
total electrical energy consumed by the heat pump system during the
same season, expressed in watt-hours."

Source: ARI Standard 210/240-2006

It's important to note that this seasonal average cost of 3.7 cents
per kWh includes the cost of supplemental or backup electric
resistance heat -- the HSPF rating incorporates this additional backup
heat into the final numbers.

In terms of natural gas, according to the DOE, Oregon residents paid
an average of a $1.43 per therm in 2006 (the average cost as of
October 2007 was $1.56). Assuming an AFUE of 90 per cent, that puts
the current cost of gas heat at 5.9 cents per kWh(e). That being the
case, the operating costs of a high efficiency natural gas furnace are
1.6 times higher than our reference heat pump.

Cheers,
Paul