Air source Heat Pumps any good?

[deema]

I’ve been asked by the head of our household to look into air source heat pumps. We are hopefully moving shortly, and she would like to have an eco friendly heating system in the new residence. I’ve done a little bit of research, and it would appear that financially they don’t financially make any sense even including the £5K government grant available.
My initial work looked at the Kw/H generated from 1 litre of oil and 1 cu ft of gas, I’ve used 60% and 90% boiler efficiency to work out how much it will cost for 10.35Kw of heating energy (equivalent to 1 litre of kerosene which my existing property uses). I’ve looked at heat air source heat pumps and used the optimistic 300% efficiency, however, my reading suggests that this drops down to say 200% (and lower) which I haven’t used) when the air is cool in Winter. The saving with todays high energy costs means that it won’t break even for say 15 years. In fact if the house is highly insulated I will be dead before it breaks even. If I look at energy prices before Ukraine, and oil is going back down in price, the payback is again ridiculous / if ever.

It seems that an efficient air source system needs to run as c40C which is too low for hot water so you need an immersion heater to top up the hot water tanks to stop legionnaires growing (which isn’t I believe included in the 300% efficiency figures quoted). The radiators need to be much larger than for a gas / oil boiler and preferably it should be underfloor if you are to attain the same room temperature. Now my wifey likes it warm (a career running hospitals has made her acclimatised to the heat before anyone suggests running the house at a lower temperature)…..around 22C which isn‘t a big temperature differential for a 40C system, I’m actually wondering in a house that may not be very thermal efficient if it will be possible to attain this room temperature.

Has anyone else looked at how cost effective moving to air source is? Am I missing something?

Whats people experiences, the good the bad and the down right ugly in installing and running such systems?

 

[Fitzroy]

This thread was about the samilar (same/similar) subject just recently. You have however reached the same conclusion that I got to, from a basic economic analysis ie cost vs return, it's a tough sell.

The things that are more difficult to estimate:
- It is likely to add value to your house as it becomes a more desirable requirement, or if the government begins to mandate a transition then houses without are likely to be discounted by the cost of install by new buyers.
- The future differential between gas and electricity prices could grow significantly. I'd not be surprised to see taxes grow on gas/hydrocarbons, so as the electricity supply moves away from gas/hydrocarbon as it's energy source this differential will increase.

Fitz.

 

[mikej460]

The biggest hurdle is that are very expensive, you will need larger, much more expensive, low temperature, high efficiency radiators and/or underfloor heating. Also it still need electricity to power the compressor so unless your new house is super-insulated this will result in very high electricity costs to maintain the house at 22 degrees and also preheat your HW. All this put us off ASHP and we bought a Wood Pellet Biomass boiler instead which, after 7 years use, is now costing 30% more for pellets than the same time last year. In cashflow terms the cost of the pellets is covered by our RHI grant but this ends in December. That said we use 8 pallets of pellets per year at £395 (current price) so £3160 pa to heat a largish 3 bedroom cottage; they are bound go up more in 2023.

 

[AJB Temple]

This was also on radio 4 yesterday. An added aspect is that as it currently costs more to run an ASHP than gas, the energy efficiency rating required for selling a house is actually worse for an ASHP set up.

Personally, unless I had a wind turbine and solar already to provide electricity, I would not dream of installing an ASHP. I would look at a GSHP if I were building a new passive house and could spec the heat ducting system from scratch.

ASHPs are, I might suggest, promoted by politicians who don't have a clue how they work. Comparisons with fridges, which are often heard, including on the programme yesterday, are absolutely stupid. A fridge is a small, very efficiently sealed, highly insulated double skinned box. Unless your house is similar, and 99% are not, then the comparison is just misleading nonsense.

 

[Nic Rhodes]

I use an ASHP to heat an outdoor swimming pool but would be very reluctant to recommend them to a domestic user atm.

 

[Lorenzl]

It is funny the electric boiler I am going to install is stated as 100% efficient BUT it is only gets a "ErP Rating D(Heating) A(Hot Water)" as :

So, while an electric boiler can heat water with little to no heat loss, giving the unit a 99-100% efficiency, the fuel factor sees the ErP rating appear low as the generation back at the power station produces high volumes of carbon.

from the Boiler guide website

This can be a bit deceiving when searching for an electric boiler.

 

[D_W]

I have an ashp mini split on a supplemental room (not tied in to the main gas/house ac unit). This is a small house, too, so it's just circumstance, not gluttony.

Mine is a 14 EER/ 21 SEER 15kbtu mitsubishi that's been in place for about 7 years. I have given up on the idea of routine maintenance - it's a wallet emptier. with the exception of cleaning the screen and if the unit ever gets weak and needs a charge, I will do that.

The reason? The installation is dead simple and I will just replace the thing if it craps out in 15 years.

Which brings me to my next point - FIL and two BILs, all same side of the family, have full house GSHP replacing oil in two cases and propane in another - the three can all be expensive here and leave you finding A/C elsewhere.

They have had good experience except all three have had the same warranty repair to a defective board - each has a gaggle of boards and is complex. when the boards fail, the service techs have trouble getting the right board ordered and installed and configured back to the systems because they're efficient, but also want to be everything to everyone (enormous number of zones, wanting connectivity with devices, etc). Cost of their systems was incurred in an area that's not heavily union and probably on the low side. 3 well vertical, I believe, maybe 4 for one of them, and the total cost was about $16k on average.

The installing company insists on servicing them once a year, and they charge $300 for it. I have no idea what they do, and neither does my FIL - and he is cheap (eventually convinced his prior plumber to show him how to clean an oil furnace himself annually - he is cheap, but diligent).

If you're somewhere cold and you want year-around efficiency, GSHP will do it. But I understand there is an effective life on the wells before something fails in them and they need to be redone. Maybe 20 years?

 

[D_W]

It is funny the electric boiler I am going to install is stated as 100% efficient BUT it is only gets a "ErP Rating D(Heating) A(Hot Water)" as :

from the Boiler guide website

This can be a bit deceiving when searching for an electric boiler.

if this is resistive heat, that figure is damning as even an ASHP will beat it by about 3 times in most conditions, two in very cold.

I'm in the states, and my ASHP mini will run down to -13F and I've never noticed a big change in the electric bill. I heats about 225 SF that's off the house for around $25-$30 a month in electricity. It shines in the summer as the cooling rating is done at 97F, which it rarely gets to here, and it will generate closer to 20k btu on 1 kw on most days.

ASHPs are run in up cost to a ridiculous level, though. The local mitsu dealer wanted $6k to install the unit that I have. The contractor I used to finish out my back room gave me his plumbing supply place's contact info to order through him and the unit cost $2100. $200 for electrical run to it and a whip disconnect and the contractor's HVAC guy installed the thing for $750 (4 hours of work for an older plumber and his helper, and they could've done what they did in 1 - they were slow and then spent 2 hours playing with the unit I think more out of curiosity). I could have and should have installed it.

 

[rogxwhit]

No experience or answers but a couple of links that may (or may not!) assist your research -

1. http://www.greenbuildingforum.co.uk...source+heat+pump&Type=Topics&btnSubmit=Search
2.

 

[Trainee neophyte]

As someone who heats their home at no cost from excess wood which is is a harvest byproduct, I feel for you all. Given the insane prices being quoted for fuel/electricity this winter, and the legislated requirement to change to a "greener" system, I wondered what the overall cost of buying a piece of land (or several small pieces) to coppice willow might come out at, written off over say 15 years.

https://www.thewillowbank.com/grow-your-own-firewood/
"Growing a Willow Copse is an ideal way of producing logs for your home or workshop.
100 “Super Willows” planted 1m apart in a 10m x 10m square Copse will produce 1 Tonne of seasoned firewood every five years.

Plant 5 willow Copses, harvest one each year and produce a Tonne of seasoned firewood to heat your home or workshop every winter.

Plant 10 willow Copses (1/4 Acre) and harvest 2 Tonnes of seasoned firewood each winter and so on…."

 

[Lorenzl]

I like the "a Smug Willow Copse Owner" photo. I thought burning wood was "bad" but I suppose as you are growing what you burn it must be virtually carbon neutral as they say?

What do you burn for the first 5 years?

 

[D_W]

That seems like a lot of work. I calculate a minimum for the consumption (heated with wood in the US as a kid) we had, 2 acres of clear land with good sun exposure would be required.

It would give someone some exercise, though.

Particulate pollution is drawing some notice here in the states because of the subsidy for biomass heating in public buildings. They pollute far more than burning natural gas, and at this point, even vs. oil. Solving that will just add to their disadvantage.

 

[Sideways]

Heat pumps as a retrofit to an existing house don't make sense to me, but I do wonder about simple aircon fed from our solar, as a supplement to the gas boiler.
A quality 6kW mitsubishi split with two indoor units cost about £2k plus installation.
These can be run as a cooler or a glorified fan heater with (by the look of things) a 300% COP most of the year in the UK. A lot of asia uses split aircon units for heating through winters colder than ours....
For just a modest outlay I suspect I'd get quite a lot of free heating from one of these and a useful reduction in the gas bill over the year. Once you have solar PV it's all about using up what it generates.

 

[D_W]

Heat pumps as a retrofit to an existing house don't make sense to me, but I do wonder about simple aircon fed from our solar, as a supplement to the gas boiler.
A quality 6kW mitsubishi split with two indoor units cost about £2k plus installation.
These can be run as a cooler or a glorified fan heater with (by the look of things) a 300% COP most of the year in the UK. A lot of asia uses split aircon units for heating through winters colder than ours....
For just a modest outlay I suspect I'd get quite a lot of free heating from one of these and a useful reduction in the gas bill over the year. Once you have solar PV it's all about using up what it generates.

I'm guessing that your 6kw rating would be in line with what my unit is (with coil running, mine will go to 2kw, but it is uncommon for it to draw like that. without coil, it seems to be more around 1kw - its consumption without coil going all out..

Effective heat output is the same as 3 -4 times that of the portable plug in heaters that run around 1500 watts, same output but 2kw (for the split) when it's cold enough for the coil preheater.

The draw for the machines in asia is probably that they're not that demanding in current draw, and they can be installed pretty much through any small hole and set up without having exhaust or much relief from a building.

Not sure on gas costs, but could be used effectively to heat a point and area around it to normal comfort and wind the gas back everywhere else.

 

[Jacob]

Woodworkers need woodburners. I don't do a lot nowadays but even that can produce sawdust, chippings, offcuts to keep the fire burning for some time. I also collect anything going including pallets and old bits of furniture and people bring it in knowing we'll have it.
The burner is a Dowling Sumo which is supposed to do 12kw and gets hot in a few minutes. The squat shape suits sawdust as well as everything else. Also coal, though never tried it.
The only prob could be storage but I've got lots of room luckily.
Also does old cardboard, paper etc which get the room hot very quickly.
Very efficient, hot, zero carbon, free fuel
PS and a smaller Dowling Firebug in the workshop

 

[Inspector]

Can't say about your jurisdictions but many of the Canadian cities have banned wood burning fireplaces, wood stoves etc because of the smoke particle pollution and even fire pits in the backyard are only allowed if permits are taken and nobody complains. Then there are the insurance companies that will either outright refuse to insure or have extortionist rates for any kind of wood heat in the workshop. They don't make it easy to heat inexpensively.

Pete

 

[Dee J]

As a (now ex) electrician I have been involved in projects involving Air source (Air to water) heat pumps to provide space and water heating. There capital cost, even taking into account financial inducements have been brutal and the installations over complicated. Even when working at their best they're pretty expensive to run and I shudder to think what future maintenance /repair costs might be when the controls stats valves pumps etc start to play up. For myself, with a small house and two occupants with a low hot water requirement - shower and washbasin only (the dishwasher and washing machine are cold fill) I've come to the conclusion that a much cheaper and simpler air - air unit would provide sufficient space heating and just use a small electrically heated tank for hot water. Any 'spare money' would be better spent on pv panels.

 

[clogs]

over the years of looking at these systems, the only way they make sense is if ur house was built as a super insulated property ...this includes triple galazing with solar gain glass and the list is endless....retro fitting is not an efficient option esp with the avg Brit housing stock.....
with a sup/ins house u dont need any of those expensive heat pumps etc anyway.....u could just use a couple of oil radiators.....cheap as chips...
I worry about the maintainence and break downs......
esp if u need a so called heating engineer....
but who's got the money for all this...?.

u have to make do with what u have....
if I was back in the UK...(that will never happen) I'd just heat the rooms I need to use....
AND wear a jumper.....
my Dutch friend in warm SW France has such a heating system but when he put in the new floors (barn conversion) he piped it up underfloor.....all the years I've known him he's had to pay extra for wood to burn (top up heating) plus elec for the emersion heater.....so what's the point....?
Elec solar roof panels were not available at the time of his conversion....
His conclusion when it eventually breaks he'll bin it and fit a wood burning boiler....
simples.....
If u wanna save money I think the best option is elec roof panels or move somewhere warmer...lol.

we just had the worst winter in 35 years, so had to burn 2.5 - 3 ton of olive wood.....
norm winter is 1-1,5.....BUT we live in the sticks and thats what every body does for heating n hot water....
Next year we'll have solar panels (off grid) and that will help us a lot.....

 

[baldkev]

I believe a u.s based company is working at ways to make heat pumps viable.... bill gates is apparently backing them, but i dont know the specifics

 

[Sideways]

A really high quality solar install is costing me £24k ish for 9kW peak, 16kWh of batteries + smart controls and charging. It's a lot of money but in the last 4 months alone it's produced 3.6MWh which was our entire annual elec consumption last year. It will do even more when the batteries arrive from China.
This project is a leap of faith as to whether it ever really pays back, but do this when you retire, maybe earlier, and it should last your lifetime.
I wonder how much heat pump systems cost in comparison and how much energy they provide. And 7 yr warranty at best (?) vs 25 year for solar panels.

The great thing about PV is that the energy is very high grade so if you want your water boiling, you can have it that way.
The downside is that 8kWh daily average in December-January will meet a lot of our needs but won't heat the house. In winter we'll still depend on gas. For 6-8 months of the year, we should be near self sufficient.

And as another benchmark, 5kW of 15 yr warranted panels, 5kWh of battery and a car charger cost a friend about £11,500 last week.