RemRate allows for a ground source heat pump and you can couple it to the domestic hot water system.  However I need to convert the Water Furnace's 5.0 COP to an equivalent EF.  Any ideas?????

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One would be tempted to put in 500%, but refrain, the stated COP is just for the unit, not the HP system, which will include pumping power and other distribution losses.  Probably system COP closer to 3.

Hi Elizabeth -- If you look at the last page of this article (, you'll see a nice description of how EF is measured.  From this, and factoring in the additional consumption that Michael mentioned, you can probably come up with a reasonable approximation of the EF for your scenario.  The toughest part may be to figure out the standby losses, if the DHW is a tank-type system.

Note that in REM the EF is entered as a decimal, not a percentage -- and for a heat pump, the decimal will be larger than 1.0.

I was looking at REM/Rate and the GSHP only needs COP entered. It looks like you only need to model the type of water heater you are using for EF and also check desuperheater in the heat pump section if they are coupled.
Also to add the pump watts. Are you using the GSHP to supply 100% of the domestic hot water?
Thanks for the help.  Didn't want to reinvent the wheel if someone had already been down this path.


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