Reply to Dual fuel (heat pump with auxiliary gas furnace) - what settings for maximum efficiency and/or cost savings?

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[quote=Anonymous]This site: 
https://ashp.neep.org/#!/product/34047/7/25000///0

Has detailed performance specs for that unit.

There are two questions: first is whether the unit has sufficient heating capacity, and the second is which is more economical to run, gas or heat pump.

The answer to the first depends upon what the heating load for your house. On that page you can put in your zip code and the heating load for your house (which your contractor should have calculated) and it will tell you how many hours a year of supplemental heat you'll need and at what temperature you will start needing supplemental heat.

If your contractor didn't calculate a heating load, or it's not available to you, this article tells how to estimate your heating load based on past energy usage and weather: 
https://www.greenbuildingadvisor.com/article/replacing-a-furnace-or-boiler

The answer to the second depends upon your local cost of electricity and gas, and the coefficient of performance (COP) of your heat pump. The COP declines as the temperature drops. The page I linked to above shows COP by temperature.

In our climate heating loads are generally higher than cooling loads, if a heat pump was sized for the cooling load it's going to need to be supplemented on the coldest days. The unit you have is rated for 33,800 BTU/hr of cooling at 95F, but only 20,600 BTU/hr of heating at 17F. [/quote]

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