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Thanks for the tip, Bob.

When we renovated our old house in 2018, I calculated with natural gas vs. electric costs in Mpls/St. Paul area, I was better off considering heating and cooling systems as being non-related. Part of that was beacuse we stuck with hydronic heat (I love it) and needed a better way to AC. I wasn't gonna do forced air. Rebates were irrlevant, because I designed and installed the systems as a homeowner. Rebates only went to professionally installed systems, and my equipment isn't under waranty since it was a DIY install (which is why I avoid certain brands like the plague…)

EDIT: I started investigating current Federal tax credits for energy efficient home improvements, and it looks like you can get credit for the equipoment without it having to be part of a professionally installed package. That is encouraging! (Wanna bet on how long until that gets axed? 😉)

I have another question: Do hybrid systems usually have the ability to control them so you can run the HP in shoulder season, switch to gas during 'normal' winter, and then add the HP back in (even at low COP) to get you through the coldest days? That's what I was hoping for, because It might let me use a smaller NG furnace with an effectively greater turn-down 90% of the time.

If I had to run a 'cold weather' rated HP at low COP for a few days here and there to keep indoor temps up, fine. If they can't be controlled at both ends, then I'm back to size the furnace for coldest design temp, size the AC for hottest design tmep, and don't worry about the condenser running in reverse.

look at the rebates and incentives for the hp option www.dsireusa.org. I got a utility rebate, federal tax, and also a state energy upgrade rebate. close to 2 grand in all.

I have a few week on this new Amana HP system with gas furnace. The gas takes over at 40 degrees, it is adjustable, 40 is what the installer runs on her own system.

So far I have been very pleased with the variable speed blower. It seems to run most of the time with weather in the 90, it does ramp down in the evening. I also have it set to run the fan every hour for 10 minutes to filter the air

The outdoor it is much quieter compared to the old Tempstar

Ed - Thanks for the advice. Yes, I need to 'run the numbers' both for final system sizing and $$ saved during use vs. $$ spent upfront and on maintenance. I have no real qualms about installing, monitoring, or maintaining any system, but nothing pisses me off more than hardware that fails 'early and often.' Especially when I spend a lot of time to set up a system.

I installed a 4-zone Mitsu split system in when we renovated our 1915 house a few years ago. ~18 SEER and rated down to maybe +% for 100% heat output. It works really well for cooling. All the multi-splits I found were reversible heat pumps, so I looking for an AC only unit wasn't a factor.

We never use the split system for heat - not even during shoulder season. The NG mod-con with 10:1 turndown and constant pressure/variable flow circ pump covers heating for less $$ at any outdoor temp.

You have me thinking 'Option 1' is the way to go for the forced air stem at the shop: Cover heat with the NG furnace, and cool with AC-only unit. My brother-in-law has a modulating gas furnace in his house. He's not sure it saves much $$ over a two-stage gas valve, but with the modulating burner and variable speed blower, he says heat is very consistent. Analogously, I'll probably go with an inverter AC. Bang-on/bang-off can go away for most any control system these days. PID and decent programming can be very reliable, and is definitely easier on equipment and more energy efficient.

Setup: My studio/workshop is an ~2400 sq. ft 1904 church. (1200 sq ft up, 1200 sq ft down). The current NG furnace is a 92% single-stage unit from the late 90's. It runs OK, but is showing it's age. The envelope is tight: I've made extensive improvements to insulation, glazing, spiral supply and return ductwork with additional filters at wall returns besides the one at the furnace return box. The building doesn't have AC, and needs it to get through the dog days of Summer. Near St. Paul Mn, with -12F Winter/90F Summer design temps.

Let's say I can get by with 80kBTU at coldest design day, and 36k(3-ton) btuh for cooling. I haven't done a Schedule J, and I will. I'm sure the 'guesstimate' is in the ballpark.

I am looking at options for a new, high-efficiency NG furnace, evaporator atop, and outdoor condenser. Options I'm looking at:

1. 100k 2-stage or modulating furnace with variable speed blower + 3-ton inverter AC only condenser.
2. 100k 2-stage or modulating furnace with variable speed blower + 3-ton inverter heat pump (HP good to +5F)
3. 80k 2-stage or modulating furnace with variable speed blower + 3-ton inverter heat pump (HP good to -20F)

Any opinions on which option to select, or whether I should looking at something else?

I'm not so sure the 10:4 I'd get in a modulating furnace vs 10:6 for a two-stage furnace is worth the added expense and risk of failure.

For Option 3, I'd think a -15/-20F HP to make up 20k btuh from going with a smaller furnace would be a given. I've had standard splits just shut down when outdoor temps go below +5. Pretty sure that was controller driven: 'hard stop at +5, don't even try…'

Thank you!