Reverse engineer a replacement heat pump size based on KW and degree days

[patman]

Our house was built 8 years ago and I’m planning on replacing my resistance boiler with an air-to-water heat pump. Like most homes, our heating system was designed with a heat loss estimate.  I started thinking that I should be able to combine the data stored by the emporia app with heat loss data for my area to extrapolate what I would need for a replacement boiler more accurately than the estimate before our house was even built.  Would that work? I’m not sure how I would even calculate it. Any ideas?

[fclauson]

Can I suggest you do a Passive House Calculation – look at saving energy before replacing a heating unit

https://passivehouse-international.org/index.php?page_id=266

[Peter]

I have a 1957 built home with gas hydronic heat in the slab and second floor ceiling. I was able to get a heat loss figure in therms/degree day by using 24 months of utility bills.

[JimiH]

I find your idea interesting.

That being said, I’m a HVAC contractor that has been doing Manual J and Manual M load calculations for over 40 years.

The big issue with contractors doing load calculations and then installing a system is they ALWAYS install more than is needed to cover their (you know what)

That being said I would start with a new Manual J load calculation and then maybe extrapolate your actual heating system usage based on degree days and compare the 2.

I have had customers use this to find out the load on their own homes. It seems pretty accurate.

https://www.coolcalc.com/

[Author]

Posts