Anyone added mini split heat pumps for supplemental heat? Did they save $$$?

jlonj

I’m considering installing mini splits, mostly for air conditioning, but I like the idea of using them for heat during the shoulder seasons. I’ll actually probably get the hyper-heat models just as a backup if my boiler ever breaks down, but I have a pretty new Weil McClain EG65 82% steam boiler, so I’m not super worried about that.

But I want to understand energy savings before I pull the trigger. I’ve read these heat pumps are much more efficient in above freezing conditions, but I’m having trouble actually figuring out what savings I can expect. Is it like $500/year? Or like $50/year? Because obviously the former would make me pull the trigger faster.

Thanks!

Condoman

I just did that. Had 2 window units and replaced with 3 wall mount 7K, 1 for each bedroom. Outside 24K, all Fujitsu.

Did it for the A/C but will be looking at how it helps the oil fired baseboard. It already helps for on demand heating in the room farthest from the stat.

GroundUp

Check the COP on the units at X outdoor temp. I recently picked up a 3 ton Panasonic for my shop mostly for AC, but as you said it'd be neat to have some supplemental heat in the shoulder seasons as well. I heat the shop with a radiant floor, fed from an outdoor wood boiler, with an electric boiler inside (for shoulder/backup, when it's too warm during the day to bother with wood). The way I understand, the COP on any electric resistance unit should be 1.0, meaning 100% efficient. My Panasonic has a COP of 3.2 at 30 degrees, meaning 320% efficient, thus costing 69% less to operate than electric resistance. I'm not 100% certain, but that's how I understand it all. I'm hoping to use it down to about 20 degrees when I light the OWB, unless the floor is uncomfortable and I need to use the electric boiler anyway

mikeg2015

I have a conventional split downstairs and wish I had installed a multi head minisplit system upstairs instead of my high velocity system. WOuld be a lot more efficient and I could zone it. 60% of the time it’s unoccupied and even we don’t use 2of the bedrooms unless we have guests. The other is a laundry room that’s all shaded after 10AM.

Below about 20-30F, when you add in defrost energy requirements, the boiler will be cheaper to operate. Above 30F, boiler standby losses are significant, so real delivery economy is lower than 82%, unless the boiler was installed in your living room... which for us steam nerds would be pretty cool.


The challenge with mini’s is very small rooms like bathrooms.

Ideal would be a air exchanger with a diverter When unoccupied it recirculates to a hallway dump zone, then a motion sensor turns on the outside air intake fan. Could have an entropy sensor and also act as an economizer. Wouldn’t be cheap but better than adding more indoor units.

HVACNUT

Look into Daikin and Mitsubishi. They both have ductless systems now that offer what equates to their version of a fossil fuel kit. All wired to their 2 stage thermostat, you can set up for auto change over to steam at X outdoor temperature or differential.

BobC

I installed a COP 3 Mitsubishi 3 years ago to cool the downstairs (to old to wrestle the old 14k window rattler in and out of the window) I got the heat cool optionand it probably saves a couple of hundred a year because I use it when temperatures are the mid 30's or above. I've used it exclusively about half the time in the last 10 days

I give half that back for yearly service and if anything major goes wrong they are very expensive to fix. If you get one make sure it's a good brand and it's installed right - Daikin, Fujitsu and Mitsubishi.

Bob

GW

Your question has lots of variables.
You have natural gas? Nat gas is the cheapest means of heating in the North (you didn’t mention where you’re from)

You have a one zone steam system? Most people that wish to save in energy costs will stoke up a room or two (or more, you choose) with ductless and let the rest of the house be a bit cooler, thus saving money.

If you have oil or even worse propane, it’s less hard to save lots of money in heating costs. Some people pay $4 gallon for propane. That’s crazy; those people really need ductless

A large amount of people get really confused between cold weather performance (how many BTU it can make) vs how efficient it is at super cold temps. COP drops as it gets colder and colder. Ductless manufactures do not do backflips to advertise that fact. Super cold maybe 1.5 or 2 COP. It’s 3 or 3.5 in the 30s and 40s.

You need a spreadsheet to plot out the running costs (electricity and gas have different costs and different BTU values)
Maybe someday someone will make a simple app to do this quickly

Most installers do a good job. Hire a goon and you’ll have many regrets.

DJDrew

We went with a 4 head Mitsubishi system, primarily for AC, but also for shoulder-season and supplemental heat.

We have an 82.1% efficient boiler for hot water heat and it does a great job at keeping the house warm, but we usually leave it set at 67 or 68. Having toddlers and infants, the wife likes keeping the kids rooms 70 all winter long and we were originally using portable space heaters to supplement so the whole house wasn't 70 degrees; the Mitsubishi mini splits solved that safety issue and likely more efficient too.

Overall, I have noticed they have decreased the gas bill some with the shoulder season use, but it's like running an air conditioner year round on the electric bill since the kids rooms need more heat. So instead of Paul getting the money, Peter gets the money.

We struggled deciding between the Hyper Heat model and the standard Mitsubishi heat pump. Since the overall 4-head system wouldn't provide enough BTUs for the whole house even at full capacity with Hyper Heat, we opted for the standard heat pump and saved 10%. Our thinking was the standard heat pump put out half of the overall system BTUs at 5 degrees and since we only needed supplemental heat in the two bedrooms with their smallest mini split heads, it was still more than adequate to provide the necessary heat - even at 5 degrees. While we felt confident in that decision during the summer, we are second guessing that now. The system put out the needed heat, but I wonder if the hyper heat system would have put out heat more efficiently as it got colder and have lowered our electric bill?

Someone on this site posted an excel spreadsheet recently for Heating Fuel Comparison Calculator. When I plugged in our numbers, running the mini splits, during shoulder season use, is roughly two dollars cheaper when comparing the Fuel Cost Per Million Btu (dollars).

starise

I have put several of these in, although not in my own home. I am planning to put one in my new addition because my existing system would have been over taxed. You really need to look closer at the numbers for your home to get an exact savings.

Do they save money? Yes. The more recent heat pumps are capable to provide heat from the ref circuit down to much lower than that.

The service factor is another issue. These are about as close to a throw away air conditioner as you can get. They are designed with a life expectancy in mind. They are good for what they do. I would buy from a local vendor who stocks the parts. Working on these is often like working on a toy. Lots of plastics and flimsy fittings.

They do what they do. After 8 or 10 years figure on replacing it. Hope it doesn't break down. If they didn't hold up fairly well, they would not be so popular. There are some bad stories out there too. Get someone skilled to install it or install it yourself if qualified. All it takes is one bungle from an inexperienced installer to cost more $$.

rsilvers

Impossible to answer without you saying how much you pay for electric and your unknown existing fuel.

In my state of MA, at January 2022 prices, Natural Gas is cheapest. Oil is double natural gas. Propane and Heat Pump are equal at about 30% more than Oil. Resistance electric is double anything else as it has been ever since I was a little kid and that was all we had.

So Heat Pump is up there with Propane as one of the expensive ways to heat.

Hot_water_fan

I ripped out a natural gas furnace for a hyper heat unit, saving about 20% despite a colder winter. 

wmgeorge

As a old HVAC guy who learned to hate air to air HPs back in the 70s and 80s. The mini splits are much improved, I installed a Mitsubishi Hi 2 on my back porch, regardless of what you hear it struggles below say 10 Deg F and mine does not have back up. Does a wonderful job 10 degrees plus and on AC.

But my indoor fan blower wheel in spite of regular cleaning of the thin, nearly useless OEM filter was packed, Packed full of dirt and other on the wheel fins. I cleaned with high pressure compressed air and then needed to clean the porch ! Yes they sell Bib kits with a sprayer to clean and for next time I have a canister filled with soapy water, power with compressed air, sprayer.

So complex and expensive to repair IF you have issues, and the multi head units can be a nightmare to service. Regardless they are a 200% improvement over the ones I had to service and hear the complaints about in the 1970s and 80s. I rarely worked on residential most were commercial units.

I am trying a filter coat spray on my filters to see if that will help reduce the cleaning of the unit.
Just one link to a Bib Kit >https://www.speedclean.com/product/mini-split-bib-kit-xl/

Here is the Fuel Cost calculator stolen from the State of Maine website:

BobC

I installed my heat pump mini in 2015 to cool the first floor of the house and maybe handle the shoulder seasons. It cools very well but is to small to heat the fist floor space when its below about 25 degrees (100 year old house, keeps weather out not so much the cold). I do not consider heat pumps suitable for full time use in this climate. Use any money a really good heatpump system would cost and get the building up to snuff.

It saves money when it comes to cooling and does the shoulder seasons well because I'm only handling the first floor. If I had the capacity for the whole house I think I would save some money but that money would quickly be eaten up if it required a service call. It's much easier to find a qualifies steam man in Boston than a qualified minisplit man.

Since 1981 I've had one service call on my steam system (because I was sick at the time), with gas whatever yearly service you need can pretty much be handled by a reasonably bright guy on his own. When I was on oil I had the system serviced every year in the summer.

Energy prices in the Boston area are very high - oil is $3.49 a gallon, nat gas is $1.90 per therm, electricity costs me $0.253 per KWH and I locked prices in a year ago so a lot are paying considerable more. Even with a cop of 3 a heat pump is still more expensive than a gas boiler for heat, you can save money if you use a heat pump to heat an area and let the rest of the house drift lower on mild winter days. It all depends on what the energy costs are where you live.

ethicalpaul

Heat pump is 30% more expensive than oil? Something’s wrong with that heat pump.

wmgeorge

I pay 9 cents per kWh, some here pay 22 cents, it all depends on the cost per Btu. The calculator I posted above does that for you.

pecmsg

ethicalpaul said:

Heat pump is 30% more expensive than oil? Something’s wrong with that heat pump.

Oil twice the cost of NG is also questionable!

Someone needs to check the BTU per therm, gal and KW

wmgeorge

pecmsg said:

ethicalpaul said:

Heat pump is 30% more expensive than oil? Something’s wrong with that heat pump.

Oil twice the cost of NG is also questionable!

Someone needs to check the BTU per therm, gal and KW

You do have Excel don't you? Use the file below.

pecmsg

wmgeorge said:

I pay 9 cents per kWh, some here pay 22 cents, it all depends on the cost per Btu. The calculator I posted above does that for you.

What about all the other fees that are added on per KW?

ethicalpaul

pecmsg said:

ethicalpaul said:

Heat pump is 30% more expensive than oil? Something’s wrong with that heat pump.

Oil twice the cost of NG is also questionable!

Someone needs to check the BTU per therm, gal and KW

It's funny, I don't have any trouble believing that one!

Robert_25

My electric cost averages $0.10 to $0.12 per kwh depending on time of year and how much we use. That is total bill divided by total kwh, so inclusive of all fees. We have a 2 ton minisplit that we purchased mainly for AC, but I have found it to be very economical for heating the house in the fall and spring. With current oil prices the minisplit costs about half as much to run.

wmgeorge

pecmsg said:

wmgeorge said:

I pay 9 cents per kWh, some here pay 22 cents, it all depends on the cost per Btu. The calculator I posted above does that for you.

What about all the other fees that are added on per KW?

All the fees are included, Mid American gets most of its power from wind generation.
Nat gas cost is way out of line considering its basically a burn off or surplus from oil drilling. Oil has always been expensive it seems.

pecmsg

wmgeorge said:

pecmsg said:

wmgeorge said:

I pay 9 cents per kWh, some here pay 22 cents, it all depends on the cost per Btu. The calculator I posted above does that for you.

What about all the other fees that are added on per KW?

All the fees are included, Mid American gets most of its power from wind generation.
Nat gas cost is way out of line considering its basically a burn off or surplus from oil drilling. Oil has always been expensive it seems.

then you must have the cheapest electric rates in the country!

DJD775

pecmsg said:

ethicalpaul said:

Heat pump is 30% more expensive than oil? Something’s wrong with that heat pump.

Oil twice the cost of NG is also questionable!

Someone needs to check the BTU per therm, gal and KW

Funny you say that. Here in RI my father in law just told what he paid for NG in December and for a similar size house + a heated finished basement and he's paying ~ half what i'm paying for oil. Not exactly apples to apples as I have a normal efficiency oil boiler with an indirect and he has high efficiency forced hot air with a separate NG water heater. He also cooks with NG. This has been the case with other friends I know but his was the first that I've actually seen the bill.

ayetchvacker

jlonj said:

I’m considering installing mini splits, mostly for air conditioning, but I like the idea of using them for heat during the shoulder seasons. I’ll actually probably get the hyper-heat models just as a backup if my boiler ever breaks down, but I have a pretty new Weil McClain EG65 82% steam boiler, so I’m not super worried about that.

But I want to understand energy savings before I pull the trigger. I’ve read these heat pumps are much more efficient in above freezing conditions, but I’m having trouble actually figuring out what savings I can expect. Is it like $500/year? Or like $50/year? Because obviously the former would make me pull the trigger faster.

Thanks!

I have many customers here in central PA who have similar systems. What you’re describing makes the heat pump the primary and the steam would be the secondary or back up for use as needed in the case the heat pump does not meet demand. The answer to your question involves quite a few variables but essentially it’s going to be a great idea if you live in a cold climate. Your situation will be unique but ALL of my customers have reported they were shocked how much money they saved by using Hyper Heat Mitsubishi units for the majority of the heating season. Most of them have heating oil hydronic systems and a few NG and most are older homes (1950’s or older). Hope that helps. Just my observations. Good luck. 

wmgeorge

Here in Iowa the cost of NG has sky rocketed, its cheaper to heat with a Mini Split except when its down to 10 degrees or colder here. But when it gets really cold the HP does not extract enough heat. I have a 96% Trane 2 stage gas with a ECM motor for the main house. IF I had the money I would go GeoThermal but also lacking space for the wells or loops required.

Zman

The heat pump will save you money on the shoulder season days. You won't have the big boiler and associated pipes heating up just to bump the indoor temps up 10-20 degrees. The breakpoint where you are better off with steam will vary based on local energy prices.

fentonc

As other people have said, it's really going to come down to your electricity and natural gas costs. I'm outside of NYC and pay $0.225/kwh all-in, and $2.32/therm for gas on my last bill. I would only need to hit a COP of 2.375 for a heat pump to be cheaper than my NG hydronic system if it were actually hitting 83% efficiency, and I suspect that it's typically hitting closer to ~65% or so due to standing losses because it's so oversized, so I would probably only need a COP north of 1.85 to do better. I was looking into them primarily for A/C, but was surprised to find that the hyperheat units would probably be cheaper to operate even close to the design temperature of ~12F here.

Jamie Hall

Making any kind of generalization about energy costs and energy savings is just plain wrong, and can be very misleading to less well informed people who happen to read the article or the post on the Wall. Just plain don't do it -- it's bad enough when some talking head "expert" expounds on it.

Each individual situation -- building by building -- must be considered individually.

wmgeorge

We did pretty accurate projections using Wrightsoft Manual J and N software. You must have correct / accurate building measurements, window size and type and insulation. Not just "I think" guesses. Manual J for residential and N for commercial. You then need current energy costs and use a spreadsheet calculator like I posted above.

For my own house which I had up dated with new windows and insulation (and per Manual J) I replaced a Nat Gas 80,000 Btu 92% with a 68,000 Btu 96% my energy costs for heating are so very low people are surprised.

You also need to consider future trends in fuel costs.

Yes after working in the field for over 25 years, I taught the stuff... you'd be surprised at what You Learn by teaching! Its fun to meet former students and see them doing so well in the real world of HVAC. Makes it all worthwhile.

Correction: My new power bill I received today, I was totally wrong on our cost per kWh, I said 9 cents, wrong it comes out to 7.8 cents per kWh, gas cost per Therm $1.175 and a Therm is 100,000 BTUs

Jamie Hall

I wish I had your electricity rates, @wmgeorge . Where we are it's more like 25 cents per KWh (about $7 per 100,000 BTU) -- and scheduled to go up in the near future. Natural gas isn't obtainable at all. Oil is about $2 per 100,000 BTU (bulk buy -- spot market is around $3, but wildly variable).

Hot_water_fan

@Jamie Hall it’s so often a chicken and egg situation with electricity rates: my rates are low because our summers are hot and everyone has and uses AC. So tacking on more utilization with a heat pump should bring down rates if the utility is intelligent about matters (major caveat). 

wmgeorge

Jamie Hall said:

I wish I had your electricity rates, @wmgeorge . Where we are it's more like 25 cents per KWh (about $7 per 100,000 BTU) -- and scheduled to go up in the near future. Natural gas isn't obtainable at all. Oil is about $2 per 100,000 BTU (bulk buy -- spot market is around $3, but wildly variable).

I think that is the winter rate, never paid any attention before. I did the breakdown for my son who runs a 96% gas (I do not know the exact %) HW boiler and it also does his DHW. I said according to my calculations its cheaper this year to run Mini's, he said not. According to this he would save $4 per using the Mini's. He had the money when he built, should have gone geothermal.

Hot_water_fan

He had the money when he built, should have gone geothermal.

With the performance of air-source today, geothermal is at a major disadvantage. 

wmgeorge

But... Mini splits are suppose to last 8-10 years If you go that route. Geothermal since its All inside tend to have less service problems, once the start up is completed. Geo tends to have stable COP because ground temps don't change that much. So its going be interesting. 

Hot_water_fan

Who said minisplits? Any air source heat pump would work.

rsilvers

It you pay 8 cents for power then heat pump is cheapest. 

In MA they worked hard to push everyone to heat pump with $10,000 rebates and then raised the electric rate to 27 cents per kWh, making it equal to the cost of Propane per million BTUs and as mentioned, 30 percent more than oil. 

https://www.liberationnews.org/national-grid-to-hike-utility-prices-in-mass-and-other-deregulated-states/?amp=1

wmgeorge

Hot_water_fan said:

Who said minisplits? Any air source heat pump would work.

Hmm, you need the highest SEER you can get in a non Split HP. I see Goodman makes a 20 but you need to buy all both inside and outside units and it is expensive. . My Mini is 23% SEER, Plus when you put a HP compressor outside here in North country you need to understand its life is much shorter than a Geothermal which is inside running in nice warm, with no oil return problems. Do some research, I worked on these.

Oh and the COP, as I said up above a geo is stable running 3 or 4 because the earth temp does not change that much, any air to air HP the COP varies as to outside air temp. https://www.nordicghp.com/2015/08/how-to-calculate-coefficient-of-performance/

Hot_water_fan

@wmgeorge can you elaborate some? SEER is irrelevant to heating and having installed a ducted minisplit, it wasn’t expensive. Not important anyway if the decision comes down to ground source or air-source, since an air handler is being installed either way. I agree geothermal can be more efficient (sometimes), I challenge that it’s worth the cost of the drilling. 

wmgeorge

SEER is a rating of Seasonal Efficiency rating applies to AC and Heat Pumps, if you have a high SEER it is telling you how good it is in both modes. Same compressor and same outdoor coil and indoor coil.

According to the American Council for an Energy-Efficient Economy, you should consider buying a heat pump that is at least 15 SEER and 8.5 HSPF. The most-efficient Energy Star-rated heat pumps are 18 to 27.5 SEER and 8.5 to 12.5 HSPF.

You also need to factor in the service cost as a compressor inside or one outside. Thats why the Mini Splits only have a rated life of 8 to 10 years. Have you ever changed an air source HP compressor while standing in a snow drift? I have.

https://www.ecohome.net/guides/2241/heat-pumps-ground-source-geothermal-or-air-source-which-one-makes-more-sense/

Hot_water_fan

SEER is just cooling and is confusingly named, probably because AC came first. I agree geothermal could be potentially easier to repair. I don’t think homeowners care.

wmgeorge

Hot_water_fan said:

SEER is just cooling and is confusingly named, probably because AC came first. I agree geothermal could be potentially easier to repair. I don’t think homeowners care.

Well when I retired in 2007 homeowners cared, cared a lot about the cost and cost of ownership. In todays internet age people who spend that kind of money do a lot of online research and are very well informed. Some dealers complained the homeowner knew more about the equipment than the salesman did... not a lie and you can see that here on HH all the time with the service people!

The Loopers or Well people charged about $2000 per well which was generally good for 12,000 Btu's and that included the pipe and fusion welding. Loops were somewhat less. Both were better done during the building stage, but I have seen wells done under driveways and in back yards!

You may be out East, not even around HPs or geothermal I have no idea. But here in Iowa a lot of Geothermal and air source dual fuel gas heating is put in.