Furnace vs mini splits

[John Galt]

I’m trying to decide between a forced air propane furnace and multiple mini split units in a new construction home. Help me out please.

We have 13kw of solar panels. 24 batteries are 1110 AH at 48V. 240V available from the inverters, 8800W max. We need to run a generator a couple of times a week to charge the batteries Nov-Feb due to mountains blocking the sun for most of the day, but have excess power rest of the year. This is a stand alone system, no grid power. I plan to get a propane fired backup generator to charge the batteries when needed.

The primary heat is from a BK King on the main level. We have a Princess in the basement that is used when it gets deep in the negatives. I load the King twice a day in deep winter and once in the shoulder seasons.

The furnace/splits would be used for emergency backup, if I was injured, old enough to not want to burn, or we went out of town. The generator would kick on when needed to power either system.

I always planned on a propane furnace thinking we didn’t have the electricity to run the splits during the winter. Every room would have heat, and the entire house would be warm but I don't think I would start the furnace for any reason except those listed above, it wouldn’t be worth the cost of the propane.

On the other hand, the splits could take over in the shoulder seasons when I have plenty of power, cool on these hot days, and could be used as zoned heating in the basement without heating the entire house.

The costs would be almost the same:
The furnace would be a high efficiency model with new ducting. I would be running the ducts, the contractor would drop in the unit.
The splits would be three multi zone units with two ceiling cassettes each. I would install these, the contractor might vacuum the lines.

What am I missing?

 

[Whitenuckler]

I’m trying to decide between a forced air propane furnace and multiple mini split units in a new construction home. Help me out please.

We have 13kw of solar panels. 24 batteries are 1110 AH at 48V. 240V available from the inverters, 8800W max. We need to run a generator a couple of times a week to charge the batteries Nov-Feb due to mountains blocking the sun for most of the day, but have excess power rest of the year. This is a stand alone system, no grid power. I plan to get a propane fired backup generator to charge the batteries when needed.

The primary heat is from a BK King on the main level. We have a Princess in the basement that is used when it gets deep in the negatives. I load the King twice a day in deep winter and once in the shoulder seasons.

The furnace/splits would be used for emergency backup, if I was injured, old enough to not want to burn, or we went out of town. The generator would kick on when needed to power either system.

I always planned on a propane furnace thinking we didn’t have the electricity to run the splits during the winter. Every room would have heat, and the entire house would be warm but I don't think I would start the furnace for any reason except those listed above, it wouldn’t be worth the cost of the propane.

On the other hand, the splits could take over in the shoulder seasons when I have plenty of power, cool on these hot days, and could be used as zoned heating in the basement without heating the entire house.

The costs would be almost the same:
The furnace would be a high efficiency model with new ducting. I would be running the ducts, the contractor would drop in the unit.
The splits would be three multi zone units with two ceiling cassettes each. I would install these, the contractor might vacuum the lines.

What am I missing?

If you can I'd say get both, as if you are away and it's really cold, the heat pumps won't work so good. The heat pumps are good for AC though, so I'd get a couple for your bedroom area and hot area's. Then use them for heat when you can too. If you use your basement and don't need AC down there, then maybe just use the furnace there for heat (and wood). Probably expensive to have propane too though.
Edit: Also, if you can get ducts with the furnace that would be great for circulating the air. The furnace will draw very low power too.

 

[bogieb]

I'd think that in the deep of winter your area gets too cold for the minisplit to keep your house warm. I had a mini split put in in 2021 that is good for sown to +5*F. I don't use the mini split in anything below somewhere in the teens though. Part of that is because the defrost cycle goes on so much that it is blowing cold air fairly often so it is basically fighting itself. And part of that is the inside air doesn't "feel" warm even when the thermostat says it is 68 or 70*

And, the minisplit uses a huge amount of electricity for heat. For my 950 sq/ft house, main floor only , I use about 12kwh/day for cooling to a set temp of 74* when the temps are in the high 90's,

and with some heat coming up from the pellet stove in the basement, electric usage is 26+ kwh/day when heating in mid teens (the panels were snow covered for several days, so no production).

However, there are systems that can go to lower temps than the one I got, and they are innovating all the time so YMMV.