Heat pump vs propane

[GSPHUNTER]

You have to figure out cost of kilowatt hours, vs propane. I know when I took a class on heat pumps ( hvac tech) the instructor said at that time once it got down below 50 degrees outside, gas was more efficient. Now that was with natural gas. But the colder it gets out side, the lower the temp. of the air coming out of your ducts also. Which equates to longer run cycles in electricity. Propane would be your emergency heat or back up heat. You can get electric heat strips also in an air handler or an elec. furnace to heat the air, as primary ( use reg a/c unit) or back up heat with heat pump. We don’t install to many heat pumps here, as natural gas is readily available 99% of the time.
Mini splits are becoming more and more popular here, ( hydronic heated homes, no duct work) for a/c. Not used much if at all for heat, but they do have the ability.

I would agree with this. I worked in the A/C industry for 38 years, not including time in Navy. I am not a big heat pump fan. As Stalker69 stated you will likely need backup strip heat when the outside unit, condensing unit goes into defrost. If you know a mech. engineer have him do the calculations for you to see if it is cost effective.

 

[StuckoYota99]

To clarify ductless heat pumps do not have a back up heat source.

 

[MT_Wyatt]

Using an electric heat pump in Montana requires auxiliary heat. Propane is a great choice for that. I think adding to what you have makes sense - two different sources of heat, and use the super efficient one (heat pump) when you can.

As others noted, as temperature decline so does a heat pump’s ability to pull energy from outside and move it indoors. Variable speed inverter compressors and advanced controls have helped reduce how much capacity falls off below zero (some brands advertise something like 90% capacity around 0to -10) but a lot of those are a ductless product.

With regards to calculations - the r cycle, in reverse, is going to be quite efficient. It will surpass combustion efficiency, even in a condensing operation. I wouldn’t worry about the money or time trying to pencil that out. BUT I would pay particular attention to what those who work on these things have to say about them.
This is a decent article on them: https://www.consumerreports.org/hea...s-actually-work-in-cold-climates-a4929629430/

These products operate at some high refrigerant pressures, and aren’t super simple. But….there’s a lot of larger scale efforts to create very, very large heat pumps in Europe due to electrification and trying to get around combustion. Our Government is starting to push this very hard, to the point I think federal agencies are going to start being restricted using gas fired equipment. Our grid isn’t ready for that, so the mandates are somewhat aspirational. But it’s a “thing.”

 

[Stalker69]

To clarify ductless heat pumps do not have a back up heat source.

You better check into that deeper, because we put in mini splits a lot, and they are able to heat also.https://www.lg.com/ca_en/wall-mounted-mini-split

 

[StuckoYota99]

You better check into that deeper, because we put in mini splits a lot, and they are able to heat also.https://www.lg.com/ca_en/wall-mounted-mini-split

Yes, they heat but I meant that there isn't a auxiliary heating element like you would see on a standard forced air system. We also put in primarily Mitsubishi.

 

[whoami-72]

What's your design conditions? You can look it up at the link below. I highlighted Missoula's for example.

If you wanna dive in further let me know. I'll need the manual J the HVAC contractor did on your house and local utility billing rates

In short, heat pumps probably won't work well in your area unless you have a backup source like propane or electric resistance or get a fancy low ambient heating system. Most of the modern systems can heat pretty low at full capacity now but they dont usually go deep into the negatives. Lennox gave me a pretty cool presentation about their Canadian heat pumps which might be what youd be looking at. They went down to -25 at full capacity if memory serves correct. Also, I'm assuming Montana is like most other western states where the price of gas is cheap per BTU in comparison to other energy sources especially if you already have a 90%er. Therefore, it's probably more cost effective to stick with what you got even though youre technically using more energy. With design conditions and cost not being in your favor, you probably would only want to do it if you're trying to be green. Technically, the heat pump uses less energy and can be greener than propane if created by a renewable resource.

ASHRAE climatic design conditions 2009/2013/2017/2021

ASHRAE climatic design conditions station finder

ashrae-meteo.info

 

[CoffeeGoat]

Just another quick data point, others have discussed the efficiency and function of a heat pump but no one has mentioned the condensate issue yet. We use mini splits for heating and cooling on shipping containers (back up electric heat) here in idaho falls and we ran into some major issues with condensation. Not inside the container, but outside. Ended up with huge ice slicks, to the point where we just deactivate them once it gets below freezing, not worth the hassle.

 

[NRA4LIFE]

We needed to upgrade our entire heating/cooling system a few years ago. Our house runs on propane (furnace, hot water heater, stove, dryer, grill). A buddy of mine in Michigan who works in the business told me a Heat pump/ new propane furnace was a no brainer where we live (Western WA). The HP cools the house WAY better than the AC unit we had and much cheaper. We heat quite a bit with wood and our propane and electrical bills are much lower now.

 

[whoami-72]

Just another quick data point, others have discussed the efficiency and function of a heat pump but no one has mentioned the condensate issue yet. We use mini splits for heating and cooling on shipping containers (back up electric heat) here in idaho falls and we ran into some major issues with condensation. Not inside the container, but outside. Ended up with huge ice slicks, to the point where we just deactivate them once it gets below freezing, not worth the hassle.

Did yall get heat pumps with defrost? I always spec em with defrost and specify condensate drainage (heat trace tape if needed) for exactly this condition lol

 

[GSPHUNTER]

Just another quick data point, others have discussed the efficiency and function of a heat pump but no one has mentioned the condensate issue yet. We use mini splits for heating and cooling on shipping containers (back up electric heat) here in idaho falls and we ran into some major issues with condensation. Not inside the container, but outside. Ended up with huge ice slicks, to the point where we just deactivate them once it gets below freezing, not worth the hassle

Fact, when a heat pump is set for indoor heating, the outdoor unit, the condenser, then become the evaporator. It will need go into defrost mode when the coil start to build up ice, thus cutting off airflow across the coil. When the defrost cycle is on the water coming off the coil then runs onto the ground and freezes, which results in you falling on your ass. This is when the auxilary heat comes on, heating the house. I know for different climates there are some other factors to consider, but this is generally how the cycle works. I live in So.Cal. so generally the units don't have a defrost cycle, they just go into an off cycle allowing the coil to defrost. Once again, this is when auxiliary heat comes on.

 

[CoffeeGoat]

Did yall get heat pumps with defrost? I always spec em with defrost and specify condensate drainage (heat trace tape if needed) for exactly this condition lol

Yep, this is exactly the problem, it can be a surprisingly big puddle. The problem ends up being if you live somewhere that doesn't thaw for a long period of time it just builds up. Unless you can run the condensate to an actual drain you've got a problem. We didn't have sewer access at these systems, and often you may not have it near where you install your unit...

 

[jorswift]

I live in northeastern Indiana, have a heat pump and all electric. Our winters are not the worst, but can get cold. I will say, I put in a wood stove to offset the heat pump. Our first year, electric bill was $700 in February, on budget plan for 2000sqft home. Heat pump works great in "cool" temps, but when it gets cold, it blows "warm" air, not hot. Also, the "auxiliary" heat is killer to the budget.

I would keep your propane and offset with wood stove. Look into a mini split for AC. They are cheap enough and cool a good amount.

 

[stanginthe11s]

I say go for it. at the very least you'll have A/C. units have come a long way, and they work fine down to single digits. the biggest issue that most people have with mini splits is sizing. if the head is too small the unit will run constantly and get nowhere. if the head is too big, the unit will cycle more than it should and you will lose efficiency and get a higher bill. as long as you pay attention to sizing and leave a buffer, you will be fine.
contrary to what many believe, it is cheaper to have something running than it is to have it stop and start. the largest amperage draws occur during startup, once it is running and at operating temperature, the amperage drops considerably. the same principal applies to gas and even wood, it always takes more to start a process than it does to maintain it.

 

[sao18]

A hybrid system is really nice. Heat pump when it's cool, propane when it's cold. Max efficiency either way. I'm really pleased with mine.

This. I have a heat pump, works great till it's cold. If it's snowing we have to use alternative heating. They do okay at cooling so long as it doesn't get to hot, 90+.

 

[bobr1]

Have a Mitsubishi hyper heat Minisplit. Northern Montana. It has worked really well, rated to -13, but it does start to struggle when it starts to get sub zero. Had base board originally before heat pump and acts as a backup for when it’s really cold to augment the minisplit. Our electric coop did a free audit and we were eligible for a pretty good rebate off the minisplit. After installing the minisplit our electric bills in winter dropped about 40%. However, we plan on fixing the wood fire insert incase of loosing electricity in the winter.