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Posted by Jeffrey Lebowski on February 6, 2007, 1:46 am
> I currently have a natural gas furnace and a air-source heat pump.
> Since the effiecency of a heat pump varies on a number of factors, I
> would like to find out at what outside temperature does it become more
> COST EFFICIENT to switch over to my natural gas furnace vs air-source
> heat pump? I am pretty sure I'm going to have to create a spreadsheet
> to calculate this. That way when costs change, this would allow the
> user to know how it effects the outside temperature.
>
> Can anyone help me out or has this already been done before somewhere
> else?
>
> HeatPump variables
> HSPF
> Size of unit (in what measurement?)
> Outside temperature
> Inside temperature
> Cost of electricity
>
> Natural Gas furnace variables
> Cost of fuel
> efficiency of unit
>
> Are these the main variables needed? Where can I find the necessary
> formulas?
> I really appreciate any help that can be given. If I can figure this
> out I may be able to put up an online spreadsheet or something. Thank
> you!!!
>
Not all heat pumps are created equal...really need to look at the heat
ratings chart for the particular unit.
Given, capacity as well as cop of any heat pump will drop off where you have
lowered outside temps--what's not given is the effect of humidity....which
can form frost that will eventually impeded mass airflow....result is a
greatly reduced btu output until a defrost cycle is initiated and finally
terminates....
Units having a fairly coarse fin spacing and the newer "spine type" coil
construction appear ( at least they do to ) to perform better in the above
respect.
--
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