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This[1] diagram from the article is really the crux of why many homeowners skip the heat pump option when fitting out a home.

Notice how the promised specs, a COP of 3 at 17F outdoor and rated power, aren't achieved by a single real user?

The real users get between 1.0 and 2.3 COP.

That means the cost of your system will be approximately double to run what the manufacturers specifications claim.

The government needs to step in and force companies to measure their heat pump systems in conditions more representative of a typical installation.

[1]: https://lh5.googleusercontent.com/05uL7FR8oHB3leKUvLABRMZTJ4...



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> That means the cost of your system will be approximately double to run what the manufacturers specifications claim.

Wait, seriously? That's (a) disappointing, because I thought heat pumps were pretty great. And (b) you're absolutely right: it's misleading advertising.


Typically these systems underperform because they are tested in ideal lab conditions, but then the actual installation has lots of non-idealities (long pipes with lots of bends, dirt, dumb thermostats, wrong flow rates, poor airflow, blocked filters, things cycling on and off, etc).

The full report that the (uncited!) diagram is from is here: https://acep.uaf.edu/media/290488/Air_Source_Heat_Pump_Poten...

The report describes a few other heat pump models which do meet the advertised specs.


Thanks, that's reassuring.

Thanks for the link! I have Fujitsu which I run when outside air is above 40F. Looks like it gets an amazing COP of 5 to 6, far exceeding the spec. I have tankless hydronic heating using natural gas for most of the winter, but it couldn’t quite heat my house when temps dropped to 5F.

realistically considering equipment available today most people thinking about heat pumps in cold climates would be better served by geothermal systems than air source

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