Best Of

For your approval:

I've created a spreadsheet that models the annual electricity use for a Mitsubishi HyperHeat heat pump, in Suffolk County, for heating. Rated capacity is 54,000 BTU/hr at 47F. I used the 39,000 BTU/hr design load that @2Luckysat provided.

You can view the analysis here:

https://docs.google.com/spreadsheets/d/1d1Kox9yat2WqYWkqSIk-uqiJD0D-7eK3wQy1305sMCM/edit?usp=sharing

The tab labeled "Summary" shows the performance at each temperature between 60F and the design temperature. The calculated weighted COP is 3.1.

I used the performance data from the Neep.org site at:

https://ashp.neep.org/#!/product/156628/7/25000/95/7500/0///0

to create the performance curve that is in the tab labeled "Performance Curve," and is the basis for estimates of output and COP.

The climate data — hours per year at each temperature — also comes from Neep.org and was measured at Grabeski Airport.

I also did a similar analysis with a smaller HyperHeat unit,

https://ashp.neep.org/#!/product/156607/7/25000/95/7500/0///0

That is only rated for 40,000 BTU/hr at 47F and therefore is somewhat undersized. At temperatures below 15F it would require backup resistance heat and 1.5% of the annual heating load would have to come from backup heat. However, the smaller unit would run in a more efficient part of its range for more of the heating season, so the seasonal COP is higher — 3.4 vs 3.1 — including the electricity used for resistance heat.

What this shows me is that when it comes to looking at heat pumps, simple rules of thumb are somewhere between useless and harmful. To really get a picture of the energy usage you have to analyze a specific piece of equipment, in a specific house, in a specific location.

People tend to overestimate how cold a place is and how long it stays cold. In most places, most of your heating energy use is when the outdoor temp is well above your design temperature. Most places spend so little time at design temps that efficiency at that point simply doesn't matter.

The one number ratings are not the best but in this case the HSPF2 typically shown is for zone 4 which is the OP's area. If you look at the Carrier units I linked to earlier, their HSPF2 is 9.3 and 10. That works out to a seasonal COP of 2.73 and 2.93*. Assuming the units are sized properly, you should be able to hit that with a heat pump install.

I'm in colder climate with cheap electricity and reasonably priced natural gas. If you include the cost of meter fees, the operating cost of a heat pump VS gas is about the same.

*HSPF2 ratings assume restrictive ducting representative of typical install. If you spend some time and design those well, you get even higher efficiency for minimal cost increase.

@Roger is the winter in Long Island 30F every hour?

What are your local utility costs? Around me oil is about 3x the operating cost of a heat pump so it makes no sense for a new build.

You area already adding ducting for AC, so your additional cost is only the up charge to a heat pump which will be a fraction of the cost of oil tank, boiler, plumbing and rads.

18/BTU per sqft in zone 4 sound very high for a tight new construction. I would doublecheck the manual J assumption as something is off. It should be closer to 8-12btu/sqft.

Even assuming 39k is correct you could heat the house with a combination of:

https://ashp.neep.org/#!/product/64682/7/25000/95/7500/0///0

and

https://ashp.neep.org/#!/product/64684/7/25000/95/7500/0///0

These are modulating units, if you look at the turndown on cooling it is pretty decent so even though it is oversized for cooling load, it should still turn down enough.

My guess once you get your manual J dialed in, a single 2 or 2.5 ton cold climate heat pump can heat and cool your place without issues.

Bonus of a heat pump is the SEER rating on it is much higher than your typical AC, so your cooling costs will also be significantly less.