The issue with a heat pump is sizing, at least when I did my whole house research. Down to, say, 40F a heat pump will do exceptionally well. As it gets colder, it takes more work to compress the heat from outside.
From strictly a performance point of view, that will still always beat a
resistance heater. However, now you need a larger unit. There comes a point when you need to make a size v efficiency trade off. So, if you choose a heat pump, make sure it will generate the BTUs you need at your coldest temperature or supplement it with some resistance heating.

Peri

------ Original Message ------
From: "Cor van de Water via EV" <ev@lists.evdl.org>
To: "Electric Vehicle Discussion List" <ev@lists.evdl.org>
Cc: "Cor van de Water" <cwa...@proxim.com>
Sent: 29-Nov-17 1:31:40 AM
Subject: Re: [EVDL] Heat pump vs resistive Heater (OT, but somewhat EV related)

Heat pump heating is always more efficient than resistive heating because the losses in the pump are added to the heat output, so when temp delta increases and efficiency drops, you approach the case of the resistive heating. Most heat pumps are applied to protect from excessive pump operation and wear by adding resistance heating below certain amb temps.


Sent from my T-Mobile 4G LTE Device
-------- Original message --------From: Alan Arrison via EV <ev@lists.evdl.org> Date: 11/29/17 6:11 AM (GMT+02:00) To: ev@lists.evdl.org Cc: Alan Arrison <bigg...@comcast.net> Subject: Re: [EVDL] Heat pump vs resistive Heater (OT, but somewhat EV related)
Heat can't magically be obtained from cold air.

As the temperature drops, the pump must do a lot more work for an ever
smaller amount of heat.

Al


On 11/28/2017 11:03 PM, Bill Dube via EV wrote:
Thanks for the Wikipedia reference. Here is the link:
https://en.wikipedia.org/wiki/Heat_pump

Folks are often puzzled by the "up to 4x efficiency" of heat pumps.
"How is that even possible?" is the most common question. (And the
common sense question as well...)
Well, heat pumps do indeed deliver, typically 3x to 4x the heat as a
resistive heater given the identical wattage input, occasionally even
a bit more. They indeed work, whether you believe in the theory or not.


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