Heat Pump vs Air Conditioner?

[Telly]

When the system is on the fan is on all the time. If we go away for a week, the fan is on 24/7 even if it is not heating or cooling. We can't program the thermostat to turn on at a certain time. We're mostly home so it's not a big deal.

That sounds crazy! Thermostat not wired up correctly? Or a thermostat that is not programmed correctly, such that the FAN is programmed ON for 24/7?

Do you have the manual for the thermostat? If not, could look it up online using the manufacturer and model number.

 

[CTRetiree]

It would help if posters would post some facts about where they live. For example, I live in CT and expect 6000-6500 heating degree days per year. My cold weather K factor is around 6, so divide that into 6000 and that means I need about 1000 gallons of fuel oil per year. A gallon of heating oil provides about 138000 BTUs. A kwh provides 3412. The math is pretty easy. My Mitsubishi mini-split heat pump has a coefficient of performance (COP) of about 300% for heating. That means for each kwh in, I get 3 kwh of heat out. I am paying about 30 cents per kwh for electricity (more that most states other than Hawaii). So a gallon of heat pump BTUs is $0.30 * 138000 / (3412 * 3) = $4.04/gallon. Now the calculation is easy. If oil is less than $4.04 then electricity is cheaper to heat with.

Because CT has such high electricity prices, I stopped using the heat pump at all for heating because the equipment is more expensive that the oil burner, and unless I save a lot, it's false economy. My last fuel delivery was $5.449/gallon. So I would save about $1.40/gallon equivalent to use the heat pump. But it's April. I don't use much heat, most of the oil will go towards heating hot water. And anyway, we've had some 80+ degree weather and the A/C is already on. So I will reevaluate in the fall to see where prices are. In any case, the best time to use a heat pump for heat is in the spring & fall when the COP is the highest.

 

[Buckeye]

Heat pumps generate warm not hot air, in case that is important to you. They typically come equipped with electric resistance heating as a backup. Resistance heating is less efficient so only comes on if the heat pump is not raising interior temperature quickly enough to please the thermostat.

Another I describe electric resistance heating is "lighting dollar bills on fire!" We have two heat pumps in our home in Central Florida. Most years, there's only a couple days of the year where we have to worry about the stage 2 heat kicking on. There were a few more of those days, really nights, this year.

 

[Turbo29]

Another I describe electric resistance heating is "lighting dollar bills on fire!" We have two heat pumps in our home in Central Florida. Most years, there's only a couple days of the year where we have to worry about the stage 2 heat kicking on. There were a few more of those days, really nights, this year.

Here in the desert areas of Arizona, heat pumps aren't even equipped with backup resistance heating. On the usually less than five days it even gets down near freezing (or a little below), I have never had the heat pump not be able to keep the house warm.

 

[Redbugdave]

In central South Carolina, the temperatures do get down into the teens and the backup resistance heating comes on. We do not have many days like that, though. I did have a gas pack (propane) which was a real pain to get filled (a story on that another time), and the unit was old and starting to have problems...it was replaced...burner area getting holes. I think in the long run a heat pump is cheaper if you live in the southeast. Propane has really gone up in price.

 

[skyking1]

It would help if posters would post some facts about where they live. For example, I live in CT and expect 6000-6500 heating degree days per year. My cold weather K factor is around 6, so divide that into 6000 and that means I need about 1000 gallons of fuel oil per year. A gallon of heating oil provides about 138000 BTUs. A kwh provides 3412. The math is pretty easy. My Mitsubishi mini-split heat pump has a coefficient of performance (COP) of about 300% for heating. That means for each kwh in, I get 3 kwh of heat out. I am paying about 30 cents per kwh for electricity (more that most states other than Hawaii). So a gallon of heat pump BTUs is $0.30 * 138000 / (3412 * 3) = $4.04/gallon. Now the calculation is easy. If oil is less than $4.04 then electricity is cheaper to heat with.

Because CT has such high electricity prices, I stopped using the heat pump at all for heating because the equipment is more expensive that the oil burner, and unless I save a lot, it's false economy. My last fuel delivery was $5.449/gallon. So I would save about $1.40/gallon equivalent to use the heat pump. But it's April. I don't use much heat, most of the oil will go towards heating hot water. And anyway, we've had some 80+ degree weather and the A/C is already on. So I will reevaluate in the fall to see where prices are. In any case, the best time to use a heat pump for heat is in the spring & fall when the COP is the highest.

Thank you for doing that math. I do the same when people insist on using propane fired anything here in Washington state, with one of the lowest rates in the country. It does not take long to sort out.

 

[Mansderm]

In every house we've owned we've had central air conditioning (single stage) and a gas furnace. The (original builders grade) AC in our current house is now 10 years old and I am thinking about replacing it proactively, running it to failure in NC is probably not a good plan - so DW tells me...

I am leaning toward a two stage air conditioner, more efficient and doesn't work quite as hard as a single stage - yes, I know two stage is more expensive than single stage up front.

My local utility is pushing heat pumps, so much so they're offering incentives to homeowners for heat pumps, not traditional AC.

I thought heat pumps didn't make sense up north, but evidently I'm wrong, out of date on heat pump tech or they don't make sense without a furnace too. I've read a heat pump in cooling mode works the same as an AC. The only difference is it reverses heat exchange when the thermostat calls for heat. We'd still have a gas furnace as a heat pump alone will not provide enough heat when ambient gets too cold. OTOH what heat the heat pump does provide is more cost effective than the furnace, which would run less (and maybe last longer?). In that the heat pump would run year round, it will wear out faster than an AC. I also know that a two stage heat pump would cost more than a two stage air conditioner.

So anyone here go from AC/gas furnace to heat pump/furnace? Thoughts would be very much appreciated.

In every house we've owned we've had central air conditioning (single stage) and a gas furnace. The (original builders grade) AC in our current house is now 10 years old and I am thinking about replacing it proactively, running it to failure in NC is probably not a good plan - so DW tells me...

I am leaning toward a two stage air conditioner, more efficient and doesn't work quite as hard as a single stage - yes, I know two stage is more expensive than single stage up front.

My local utility is pushing heat pumps, so much so they're offering incentives to homeowners for heat pumps, not traditional AC.

I thought heat pumps didn't make sense up north, but evidently I'm wrong, out of date on heat pump tech or they don't make sense without a furnace too. I've read a heat pump in cooling mode works the same as an AC. The only difference is it reverses heat exchange when the thermostat calls for heat. We'd still have a gas furnace as a heat pump alone will not provide enough heat when ambient gets too cold. OTOH what heat the heat pump does provide is more cost effective than the furnace, which would run less (and maybe last longer?). In that the heat pump would run year round, it will wear out faster than an AC. I also know that a two stage heat pump would cost more than a two stage air conditioner.

So anyone here go from AC/gas furnace to heat pump/furnace? Thoughts would be very much appreciated.

It depends on where you live. And keep in mind....higher efficiency does not necessarily translate to lower bills, they are many times higher depending on your electric rates. I was living in South Carolina in an all electric house with a NON-COLD CLIMATE heat pump. When the auxiliary heat strips went on due to freezing temps, my electric bill sky rocketed. Prior to that, living in Ohio we had gas and air. Our winter rates were extremely low even in sub freezing weather because we keep it around 68. Moving back to Ohio, now with propane and air, our winter rates are very high $250-300 due to price of propane. I've had 3 big name brand companies come out to discuss heat pumps. Here's the thing....we are currently not getting the cold climate units they get in Canada. Even if you got one, finding someone who knew how to install it properly is a challenge. This is relatively new technology in the Midwest and my understanding is that installation is very key to getting the most out of your heat pump. Also, no one wants to sell it with the thermostat that the manufacturer makes. They want to sell you one the installer can control, ie. An Ecobee, on line from their offices. That's just a plain no go for us. We were already forced to do that with the electric company where they can now control our electric usage in times of peak demand. We did build a 650 square foot ADU that is well insulated and installed a Mitsubishi mini-split heat pump. It's been thru 2 winters, most recent pretty severe, and my electric went up only by about $50 per month during winter. It's very quiet and it is left at 68 degrees all the time. It is very quiet. There are ducted large Mitsubishi cold climate heat pumps available up north, but no one was installing them here yet. The other issue is the mandate to switch to a new refrigerant and so the companies are trying to get rid of their old inventory. So the question is are you getting quotes for a unit with the new or old refrigerant.? All of my estimates included continuing with my propane for back up heat, and that is likely because no one was quoting a true cold climate pump. Also, prices can be inflated due to government and electric company incentives. I think most of those expired, so prices might actually come down.

 

[FedRetired50]

About 6 years ago I replaced my upstairs whole-house 12 SEER heat pump with a low-temp 16 SEER heat pump. Installer said not to go with a higher SEER because that's when repairs get expensive and payback drops. It blows hot air, and unlike the old one that would run constantly below 20 F this one will do a 50/50 duty cycle at 20 F, and not much more at colder temps. New one will produce heat down to -7 F and I may get to that temp once a year. It has resistance backup but that only is used while the system does its defrost mode for about 10 minutes every hour or two. It has never used the backup for regular heat (I can hear the difference because the system blows harder when the resistance heat is on) even this past winter when it was single-digits for about 2 weeks. A/C mode works great, and this unit actually provides maybe 1/3 of my cooling need downstairs because the air flows down the stairs and around.

At the same time I changed my downstairs A/C to a 31 SEER mini-split heat pump. It also blows hot air and will do so to -13 F. It doesn't have resistance backup so I kept my prior gas furnace for backup. I've almost never used it, but I did multiple times this winter just to get the temp up faster in the morning when it was single-digits outside. I didn't have to, it was for my comfort. Normally I leave the furnace set for 65 as backup and my wood stove keeps it above that temp most of the time, as long as I'm home. A/C mode works great, running constantly at a low speed to maintain temp. Very quiet. I would have preferred putting mini splits in every room upstairs, too, but I couldn't justify the cost. Maybe next house.

This tech is nothing like the 1st gen systems from the 70s and 80s. I had a neighbor with a heat pump back then and their house was ... temperate. Even my old heat pump was nothing like the systems I have now. And when it comes to mini splits and cooling, it blows my mind that you can get 33 SEER now. I seriously looked into geothermal years ago and I'd never do that now. There's no need with modern air-sourced ratings, and air-sourced is so much easier to install. Geo requires coolant maintenance on top of the installation expense.

Oh, and I'm in Maryland near the PA border in a cold "bowl". It is always colder at my house than in the surrounding areas. I usually see teens to 20s, then single digits for a week and negative digits once a year. This year was much colder for longer. As for my electric bills, I've tracked my actual usage for 22 years, and there was a clear drop in my use after these units were installed. The other time I saw a clear drop was when I installed a "smart" electric water heater, it was better than the dumb water heater timer I used to use (which itself saved a noticeable amount compared to no timer at all).

 

[boont]

I have a City house and a Country house. I added heat pumps to every room at the country house. I like being able to just heat or cool each room individually, not the whole house, unless I want to do that. In winter we like to have a fireplace fire but not have to depend on lighting that in the early morning or turning on the electric heat. I just switch on the heat pump with the remote control and go back to sleep. Heat pump brand is important so ask some installer folks which they like. You do have to get used to the fact that these pumps do not turn on immediately. They take 2 or 3 minutes to start working. Not really a problem, just different. I have a friend in his 90's up there and he said, "I just leave mine on all the time." But he is smarter than I am.

 

[Gearhead Jim]

We live in the far NW 'burbs of Chicago.
We had our previous house custom built 43 years ago and very well insulated. The electric company also gave us a big discount for going with electric heat. So we had a heat pump and were reasonably happy with the performance and cost.
After about 10 years, the electric company eliminated our discount, too bad, no recourse.
Our electric bill went up by a bunch, but gas has been going up a lot lately.
An accurate decision requires the ability to predict both future gas and electric rates. Do you feel lucky?
In our smaller but less insulated "final house", we're better off with the gas furnace and separate A/C.
What I really miss is the big wood stove that could keep our previous house comfy down below 0'F, we never worried about the frequent power outages. Now, we need both gas and electric to keep the house warm in winter.