UPDATED: Air Source Heat Pumps/Air Con - Full Info & Guide, is it cheaper to run than mains gas?

BikingBud

A review by the Energy and Utilities Alliance concludes:

- Replacing a functioning gas boiler for a heat pump delivers a worse financial outcome than replacing a boiler, like-for-like, at the end of its life. This poses delivery challenges for system change, given that a street-by-street conversion to heat pumps requires premature replacement of appliances.

- Replacing a gas boiler at the end of its life is currently not a financially rational decision, under all methods of appraisal, albeit with slightly more positive outcomes than premature switching of appliance.

• If the life of a heat pump is assumed to be 25 years, with a gas boiler replaced at 15 years (and all other things being equal) for a non-subsidised installation, it requires a SCOP of over 6.0 to become financially rational. 

https://www.hvpmag.co.uk/FileManager/Newsletter_Images/eua-domesticheatingappliancesacriticalinvestmentappraisal.pdf

Reed_Richards

That's an interesting report, @BikingBud.  Basically it says you need a heat pump with a CoP of around 3.2 (my estimate from their figures for 3 & 4) to break-even with gas on running costs at April 22 SVR prices.  But because the initial cost of a heat pump is so much more than that of a gas boiler you don't recoup that initial cost unless your heat pump could achieve an unrealistically high CoP.

(Below was a copy and paste but I have had to re-edit it as superscript numerals were transmogrified into normal characters in the process). 

Assumptions:-
• Boiler replacement cost £1400, lifetime 15 years (straight swap of appliance)
• Gas boiler efficiency 92% as per ErP regulations (Boiler Plus).
• Heat pump installation cost £10,855, lifetime 15 years.   

matelodave

It's the conclusion that most of us have hadv - replacing a mains gas boiler with a heat pump is not a good idea.

It might save Co2 but it wont save money and is not a financially sound investment in the long term and its even worse if you pull out a functioning gas boiler.

It either needs a balancing of the gas/electricity price or a significant drop in the price of heatpumps and their installation costs, something akin to the price drop with solar installations over the past ten years.

John_Pierpoint

When I looked into going for broke and switching from anthracite to under floor low temperature, ground source, heat pumping, some 10 years ago:

German figures for the mean time to failure of their heat pumps was 21.5 years. Any one know the mean time to failure of a 85% efficient combi gas boiler plus the accumulated annual service charge?

HOWEVER, now that refrigeration has to be run on a swan's eggcup of "Campingaz" and our waste transfer sites are full of failed fridge-freezers; [and they can burn down a tower block of flats] does anyone know what the present life of a low temperature heat pump is likely to be?? 

This is a bit like discussing electric cars!

Reed_Richards

John_Pierpoint said:

....This is a bit like discussing electric cars!

Then you'll love this thread: https://forums.moneysavingexpert.com/discussion/6349851/which-is-greener-ashp-or-ev/p1

mnbvcxz

Oh incidentally if you have air conditioning installed it is now VAT free! Which is nice. 

(Though if you manage to buy one without installation you still pay VAT.)

jcontest

John_Pierpoint said:

When I looked into going for broke and switching from anthracite to under floor low temperature, ground source, heat pumping, some 10 years ago:

German figures for the mean time to failure of their heat pumps was 21.5 years. Any one know the mean time to failure of a 85% efficient combi gas boiler plus the accumulated annual service charge?

HOWEVER, now that refrigeration has to be run on a swan's eggcup of "Campingaz" and our waste transfer sites are full of failed fridge-freezers; [and they can burn down a tower block of flats] does anyone know what the present life of a low temperature heat pump is likely to be?? 

This is a bit like discussing electric cars!

Many homes in the UK have more than on refridgeration unit.

We have/had a car with a heat pump, our fridge, and our clothes dryer (early, horrible heatpump model).

I come from a hot and humid climate where airconditioners are normal.  In fact between our buildings we had like 4 chest freezers, two top style freezer refridgerators, one central AC/Heating system, and two window AC systems.  It's not that uncommon and I know of more fires that were started from gas (butane or propane) than heat pump style systems.

Now, there are differences between fridges and AC units or "Heat Pump" units.  Fridges and small single unit AC units are virtually the same in what they do and how they do it,  Split AC systems are little to no risk as the compressor is typically outside the dwelling.  Heat pumps are I guess a little backwards as you end up with more hardware inside the house that can increase the risk.

Our old boiler (shouldn't use that word, old instant hot water heater) actually caught fire when the flow check valve got stuck in a high position causing the thing to try and make the water as hot as it could, but it built up pressure in the lines and pushed the water out past the seals on the sinks and just kept burning away, I cut the mains off outside and stopped it but honestly it was horrible.  We were forced to replace it with a modern Combi boiler due to the fact that no one would install a heat pump for us (This was a few years ago, but not that long).

Are heat exchangers a risk, sure.  Gas fires are a risk too.  In Regards to GreenFell, that fridge (much like my old instant hot water heater!) was missing some obvious design safety features.  I have seen modern AC compressors that would burn themselves out, but the good quality ones detect a problem and shut down long before a fire risk is possible.  It's not the gas inside these systems that's the fire risk either, for the fridge unit it's usually the foams they use as insulation.  This is why many say a "Solid" metal fridge is usually much safer, because that compressor doesn't touch the plastic and foam bit's that so flammable.

As electricity prices go down heat pumps become more rewarding, as natural gas price goes down (or electricity goes up) then the combi boiler wins out.  We have solar panels and that makes a difference.

Basically if someone wants to know what the best option is, the answer would be that it is different for everyone and there is no best option.

nande2000

I replaced my oil ch 8 years ago now with a Mitsubishi heat pump. It’s been flawless and was a retrofit to old rads in a 1960s detached 4 bed house. It uses about 5500 kWh per year

hebridean

An update. My soft starter munching Grant Aerona is goosed with the diagnosis being that the compressor is gone making the unit beyond economical repair.

So I'm in the process of getting a replacement and I'm going for another Grant! I know I would have preferred an Ecodan but the waiting time for one is over six months and the Grant can be had of the shelf. I've also been assured that the latest Grant's are far superior to their first offerings which were Heath Robionson esque affairs. So for those of you questioning the durability of ASHP's, I can state that it didn't quite make the ten years of full time occupancy falling short by four months. My hope is that the replacement will last at least fifteen!

matelodave

Here you go, a website with some data on actual installations - https://heatpumpmonitor.org/

It's obviously compiled by those who have put quite a bit of effort into monitoring their system performance and TBH I'm not sure how rigorously it's been collected but it does give some idea of what is possible, probably by those who've put a some effort into tweaking and optimising their systems.

If you go to the links (on the right of the table you can see the monitor outputs and there is a forum, albeit a bit skewed towards the Open Energy Monitor but there may be some hints and tips - https://community.openenergymonitor.org/c/hardware/heatpump/47