John;

This may be a bit lengthy but I'll try to explain as breifly as possible.

The only way you can compare one unit to another [efficiency] is work in the
same language. In other words, heat [btu/h]. Capacity vs. energy consumed.

To relate, a heat pump is measured in HSPF [Heating
Seasonal Performance Factor] and COP [Coefficient of Performance.] Both
have relationship [ratio] between the energy consumed vs. heat energy
delivered.

A furnace on the other hand consumes natural gas or propane gas and delivers
heat energy vs. energy consumed and has a specifiec amount of waster AFUE
[American Fuel Utilization Efficienty]

The easiest way to make a comparison is to convert the energy the 'heat
pump' uses [kWh] to btu/h. (3413 btu/h per kWh). Then compare the amount
of btu/h energy delivered to the occupied space. This is representative of
the COP. [A heat pump with a COP of say 2.0 has a 'coefficent' of 200% as
compared to a electric strip heater of the same capacity.] Keep in mind
though, that when the conditions change [outdoor temp's] the COP decreases
as well as the capacity delivered.

On the other hand, a natural gas furnace delivers the same btu/h no matter
what the outdoor temperature is. But, is either 80% efficient or 90% - 93%
depending on the model. The remainder of the which goes up the flu stack.

When you compare $ for $ [which if you ask, I will be happy to send you a
power point presentation based on the costs associated with different energy
sources and different uses] you would find a heat pump actually is just as
effient as a gas fired heater, provided it doesn't reach a low COP [low
outdoor temp's]. This 'higher efficency' state only occurrs around 70º F
ambient. When the temp. outside drops to 50º F the COP really starts to
take a dive and the gas fired furnace becomes the winner. [More efficent.]

The time to consider a heat pump is when other fuels are either expensive,
or unavailable.

I hope this is helpful.

Zyp
wrote in message
...
http://www.energyexperts.org/fuelcalc/default.asp
wants me to calculate heat pump heating efficiencies based on the AFUE of
the heat pump, but I see them measured in HSPF (Heating System Performance
Factor) at the state website which discusses rebates
http://egov.oregon.gov/ENERGY/CONS/RES/tax/HVAC.shtml

Other USENET discussions (here and elsewhere) discuss a third measure, the
COP (Coefficiency of Perfomance).

Are there conversion factors from one to the other? Given one, how can I
calculate the others?

If there is none, is there an alternate web site I can use to estimate the
result if I replace a gas furnace with a heat pump?

Thank you kindly.




--
K7AAY John Bartley Portland OR USA views are mine, all mine.
http://kiloseven.blogspot.com
"The Temporal Office says you have to do this. No, no explanation.
Here's your stuffed tuna and an airhorn." - James Nicoll