Gene: I provided that information and my cost analysis in the aforementioned discussion:

https://www.energyvanguard.com/blog/my-undersized-heat-pump-in-an-arctic-blast/#comment-32655

Gene,
I live in Long Island NY. My friends that have oil here are probably paying about the same as you. My electric cost here is $.22 . In the past I was getting at least 300 gallons a month during the winter months, and that was only for heat and DHW.
I switched to heat pumps two years ago and I calculated that my electric cost, which also includes the electric use in the rest of my house, is around $350. a month.

Jim, When posting cost comparisons between systems and fuels it’s really important that readers know what region you are talking about. I live in southern New England where oil costs a bit over $4.00 a gallon lately. I am buying electricity for $0.26 / kWh. An air source heat pump with an HSPF2= 8.8 (formerly it was the old HSPF=10.3, but that was over-optimistic), an oil heating system would cost about 13% more than the air source heat pump, so it is a long way from double the cost of the heat pump. Moreover the oil baseboard would give me a warm curtain of heat at the perimeter of every room (even small rooms like bath rooms where the heat pump does not reach). As it is I have a gas condensing boiler and we pay $1.94 /ccf for fuel, so the heat pump would cost 42% more than the gas (~$500/year). So as you see local prices matter, a lot.
BTW, those numbers for the heat pump are for just replacing the BTUs that I use now to heat with gas. But I set back 8 degrees at night on the first floor and for about 18 hours/ day on the second floor. But as you say, I would have to give up those setbacks with a heat pump, because it would not recover from the setback temperature in a reasonable time (I know… I have tried). So the 13% theoretical savings versus an oil system may disappear if I have to supply MORE BTUs with the heat pump because it has to maintain comfort conditions 24 hours a day. My conclusion is that air source heat pumps will not save money in the New England region at current fuel prices, perhaps not even for oil heated homes. Propane heated homes would have significant savings at $3.80 / gallon, but I don’t think many homes are heating that way in our region. Please, let’s all mention what region we are talking about when comparing fuel prices.

After switching my primary system from oil-fired hydronic baseboard to ducted ASHP, I abandoned nightly setbacks due to poor recovery, but the slight increase in energy consumption (over ASHP with setbacks, which still beat oil by a factor of at least two) was considerably less than the tremendous increase in comfort (air temperature vs. “mean radiant temperature of the surfaces”).

https://www.energyvanguard.com/blog/my-undersized-heat-pump-in-an-arctic-blast/#comment-32616

I haven’t run the numbers, but a residential HPWH (typically up to 80 gallons and 140°F) might store enough energy to augment low-COP setback recovery meaningfully.

https://cleantechnica.com/2023/02/28/central-heat-pump-water-heaters-can-act-as-massive-water-batteries-seattle-pilot-project-shows/

Mike, you make a good point about the EEV being an important part of the low temperature performance enhancement too. In writing my explanation, I got caught up thinking about the motors. It occurred to me that with bigger power output components the inverters can supply more power as they go above 60 Hz and speed up the motors, but what about the MOTOR size? Then it occurred to me that motors are kind of dumb in that if you give them bigger loads to move and supply them with the power, they will DO more work… until they melt. So the motors need to be upsized a bit, or at least have better cooling, which is really the same thing. But if this is happening as the outdoor conditions are getting really cold, that will help a lot to keep those motors cool as they work harder. One other thought I just had: In the case of air-to-water heat pumps making water in the 150 to 170 F range, that water could be used to cool motor heat sinks and put that waste motor heat to work.

Alison points out that “A BTU IS A BTU” no matter how you supply it. After thinking about this for a week or so, I have concluded MAYBE NOT. As I outlined in my previous comment, if we cannot do the large night setback we have been using with our boiler when we convert to a heat pump (because recovery is too slow), we now have to supply more BTUs for all those cold winter nights (when our when our heat pump has lower COP than it does in the warmer daytime hours). So we are asking for more BTUs under harder operating conditions where COPs are lower . If that isn’t bad enough, beginning this year DOE changed the heat pump rating system to give more accurate operating cost estimates. The new HSPF2 (heating system performance factor- version 2, in kBTUs-out/kWh-in) are 15% lower than the old numbers we have been using. If you get operating cost estimates based on the old HSPF, add 15%. We could avoid some of these problems If we had air-to-water heat pumps that could make 170 F hot water. We could maintain the night setback for fewer total annual BTUs and reduce cold night operating hours when COPs are lower. We still have to live with higher electric fuel costs in some areas and the more realistic, lower 2023 efficiency factors. To me, the question seems to be not whether heat pumps can supply the BTUs we need, even in the coldest weather, but can it supply them affordably on a seasonal basis? The answer I am getting in the cold northeast seems to be “not yet”. But ask me again at the end of this winter when I will have some final natural gas prices.

For the application you are describing, it is best to put volume dampers in the trunk duct as close to where they take off of the main trunk or plenum. Once air enters a duct, it is very difficult to actually prevent that air from exiting registers or diffusers. All you wind up doing is raising the system static pressure while still letting air escape through the dampers or diffusers at a higher velocity.

Gene,
I enjoyed your explanation concerning the inverter compressor to evaporate more pounds of refrigerant and multi speed fan to increase the heat exchange rate across the heat-ex coils. Just the expansion valve got short shrift. The EEV, along with maximizing the heat transfer capability of the coils it provides sufficient cool gas to maintain effective compression ratio across the compressor and to keep that speedy compressor from winding up in the scrap heap.