ASHP vs Oil in 2022

[MortarThePoint]

24 minutes ago, Marvin said:

hi @SteamyTea

 

Yes for your home but not for this house!  

 

Just like an ASHP installation, the results are affected by the ASHP model, installation, insulation, presumably an MVHR, shadowing of solar, wind, rotation, airtightness, quantity and habits of occupants and finally if the occupants have actually been informed and understand the best way to run an ASHP.  

 

Hence the problem when trying to answer the questions people ask like:  "Is a ASHP cheaper to run?" or "Will an ASHP work on my house".

 

and to get back on subject, in my humble opinion, both ASHP and Oil have their challenges and the answer depends on many individual specific items. 

 

 

I don't understand the 'is an ASHP cheaper to run' problem if using it with UFH on the correct centres. If there was a large non-linearity in it's output (i.e non-flat efficiency curve) then it would make sense. Unless you need power past the tipping point, the problem can be overcome by duty cycling can't it.

 

ASHP plus radiators, that's a different matter. 

 

Without savings associated with E7, ASHP has been and will be* more expensive to run than grid gas for all houses won't it. [* for a while at least]

 

Is it worth installing, that's harder to understand as you need to offset the capital cost.

[ReedRichards]

 

Quote

 

What’s the maximum charge for a single unit of electricity or gas from 1 October 2022?

So, from 1 October 2022, if you’re on a standard variable tariff paying by direct debit, the average unit price will be frozen at 34.0p/kWh for electricity and 10.3p/kWh for gas (including VAT).

 

7 minutes ago, MortarThePoint said:

 

Without savings associated with E7, ASHP has been and will be* more expensive to run than grid gas for all houses won't it. [* for a while at least]

 

34/10.3 = 3.30 so your heat pump would need to achieve a SCOP of better than 3.3 to make it cheaper to run than a gas boiler that is 100% efficient.

[JohnMo]

Not really, as gas is not 100% efficient, most gas boilers achieve around 85% efficiency, especially if not run on weather compensation as a single zone.

 

So you need a scop of 2.8 to match gas.

[MortarThePoint]

35 minutes ago, ReedRichards said:

34/10.3 = 3.30 so your heat pump would need to achieve a SCOP of better than 3.3 to make it cheaper to run than a gas boiler that is 100% efficient.

 

23 minutes ago, JohnMo said:

Not really, as gas is not 100% efficient, most gas boilers achieve around 85% efficiency, especially if not run on weather compensation as a single zone.

 

So you need a scop of 2.8 to match gas.

 

Fair enough, but we are in odd times and am I going to be able to get a new tariff like that (i.e new customers)?

 

Personally, I can't have grid gas anyway so the toss up is vs oil for me which is around 90p/l -> 90p / (10.35kWh/litre * 85%) = 10p/kWh of heat

Assuming an oil boiler efficiency of 85%, I need an SCOP of 2.9 or higher presuming I can get the 34p/kWh electricity tariff. 

[HughF]

12 minutes ago, MortarThePoint said:

 

 

Fair enough, but we are in odd times and am I going to be able to get a new tariff like that (i.e new customers)?

 

Personally, I can't have grid gas anyway so the toss up is vs oil for me which is around 90p/l -> 90p / (10.35kWh/litre * 85%) = 10p/kWh of heat

Assuming an oil boiler efficiency of 85%, I need an SCOP of 2.9 or higher presuming I can get the 34p/kWh electricity tariff. 

Anyone can get that rate, it’s the backstop rate….

 

scop of 2.9 is easily achievable… I wouldn’t rip out a working oil install to make a swap, but if you’re at a stage where you need a new boiler and tank then certainly consider making the move.

 

 

Edited October 7, 2022 by HughF

[George]

What's the payback time of a gas boiler?

[JohnMo]

You would have to compare that with direct electric heating. To get a pay back time.

 

So direct electric heating has 100% efficiency.

 

Say gas is 85% efficient. Gas effective gas about 12p, electric 34p

 

Then it depends on central heating cost to install compared to panel heaters at the cheapest, or cost for UFH with immersion heater. Plus DHW heater. And how much energy you use.

 

So for a like for like comparison system boiler, and UFH and hot water cylinder

£600 -1000 for a boiler, immersion for UFH £60.

 

So say 10000kWh per year.

 

0.12 X 10000=£1200

0.34 X 10000=£3400

 

So in that case not long even with an expensive boiler. A combi gas boiler would delete the cylinder, so pay back shorter again.  As it costs an extra £2200 per year to pay for electricity.  In this case even comparing panel heater to full blown central heating, pay back is a year or so.

 

20000kWh

£2400 and £7400.

 

Very low user

1000kWh

 

£120 compared to £340, so a couple of years.

 

Economy 7 changes the maths, but you have to also pay for storage heaters.

[Marvin]

3 hours ago, MortarThePoint said:

I don't understand the 'is an ASHP cheaper to run' problem if using it with UFH on the correct centres.

Hi @MortarThePoint

 

Well, it would depend on the 'AIM'  Airtightness, Insulation, Mechanical Ventilation with Heat Recovery

 

But the main thing people don't understand is that the bigger the number between the temperature outside and the set water temperature coming out of the ASHP the lower the COP (efficiency). This does not happen with a oil or gas boiler. ( it may to some degree but never twice or four time the efficiency, always below 100% efficiency)

 

My last boiler was rated at high 90s% efficiency as long as used correctly. My ASHP is capable of efficiency from 180% to 634% efficiency depending on the  difference between the temperature outside and the set water temperature coming out of the ASHP.

 

If the outside temperature was -3C and the water temperature coming out of the ASHP was 35C and sufficient to heat the building, my ASHP would achieve a better COP (rate of efficiency) than if I ran the ASHP at 45C for a shorter amount of time to achieve the same heat output.  

 

M

 

 

Edited October 7, 2022 by Marvin
clarification

[Roger440]

19 hours ago, George said:

I live in a solid wall house built in the 1880s. The ashp costs less than I used to spend on oil (although its a thermally much improved house and the old oil system was incredibly inefficient so it's a moot point). Can't hear the ashp at all from inside and when outside when immediately adjacent to it as I said, it's a noise, but it isn't noisy. 

 

 

 

It is indeed a moot point. Its like comparing apples with elephants. 

 

Your heat demand on an oil boiler would be much lower too now you have insulated.

 

You keep seeing this bandied about. You need a better insulated house so you can fit ASHP. 

 

Ive got a great idea. Do the insulation needed to make an ASHP work well, keep the boiler/heating you have and save even more money by not replacing a perfectly good heating system.

 

Maybe its me, but you keep hearing on the radio. Drives me mad.

 

Sure, on a new build with a clean sheet of paper, its a different situation.

 

As for the noise, rather going to depend on the level of background noise. Either way, not anywhere near my house. I still regret installing a sewage treatment plant for that reason. Despite the many modifications to improve it.

[George]

Edit - somehow deleted the numbers bit. 

 

I've always calculated oil and ashp to be cost neutral on running costs. Fuel oil was up to 150p last year. It came down to a pound and is around 88p on the local buying group. It really depends on boiler efficiency but both come in at around 10p/kWh delivered. I've also got solar so actual cost is lower, but that can be ignored. 

 

 

I think ultimately, all the technologies work OK with similar-ish running costs. There's an expectation placed onto 'green' technologies that they have to be more cost effective than oil and gas. But really, we should be starting from a position of should we be digging up fossilised carbon and setting fire to it if we don't have to? 

 

Part of the payback for me is I'll be able to look my children in the eye and said that when I had an investment decision, I went for the most sustainable option available at the time. 

Edited October 7, 2022 by George

[HughF]

It’s an even easier decision for us - we need to replace a 72% efficient boiler and all the rads anyway, so we might as well ditch the gas and go green as the installed costs are basically the same (parts are more expensive but my labour is free vs cheap gas boiler and paying a gas safe guy because I don’t have the certs) and the running costs will be about £600/year less.

[Spreadsheetman]

Interesting topic. I’m buying a late 70s house that has a new oil boiler+tank and as Roger440 suggests I’m going to insulate the fabric and upgrade the plumbing to make it as ASHP-ready as I can. It would be very wasteful to rip the heating system out on day 1.

 

One thing I can do soon is have the boiler jetted down to its minimum rating (it’s a 12-16kw model set to the 14kw default) as my rough estimates show about 8kW heating demand before I start adding insulation.

 

The noise question is an interesting one. There is a good test case near me where 15 sheltered housing bungalows have been built, each with a 5kw heat pump. The bungalows are really close together (in a quiet area) so it will be interesting to see what the noise level is like when they are all occupied.

[Onoff]

12 hours ago, HughF said:

It’s an even easier decision for us - we need to replace a 72% efficient boiler and all the rads anyway, so we might as well ditch the gas and go green as the installed costs are basically the same (parts are more expensive but my labour is free vs cheap gas boiler and paying a gas safe guy because I don’t have the certs) and the running costs will be about £600/year less.

 

No gas here but a 90% efficient oil boiler. It's staying for now. 

[SteamyTea]

When we see boilers have an efficient of xx%, has anyone actually measured their usage.

I often read on here that the oil burning brigade say it is hard to measure and the don't always trust the delivery quantities.

Same with gas boilers. 

And wood burners are even worse, no one bothers to weigh the amount of timber they put on, but all claim the moisture is 20% or below.

 

Edited October 8, 2022 by SteamyTea

[PhilT]

20 hours ago, MortarThePoint said:

ASHP has been and will be* more expensive to run than grid gas for all houses

The latest gen ashp models, if competently installed and set up, are much cheaper to run than the average gas boiler. At current rates mine is saving me c. £700 pa

[JohnMo]

If you save that much your heating bills must be huge or there was an issue with the old boiler or system and/or you have decreased the heat loss.

[George]

7 hours ago, Spreadsheetman said:

The noise question is an interesting one. There is a good test case near me where 15 sheltered housing bungalows have been built, each with a 5kw heat pump. The bungalows are really close together (in a quiet area) so it will be interesting to see what the noise level is like when they are all occupied.

 

My experience with a large twin fan unit is that they're not very loud and in general terms noise dissipates quickly. The time they are on most, in the winter, is the time you are outside least. In summer it is only for hot water and has highest COP. 

[HughF]

On 07/10/2022 at 17:32, George said:

What's the payback time of a gas boiler?

Compared to what alternative? 
 

If you’re talking gas boiler upgrades, It has long been known that you will never payback the installation cost in gas savings from a boiler upgrade, despite what anyone will tell you. You could call it ‘The great condensing boiler myth’…

 

 

 

 

[HughF]

18 hours ago, JohnMo said:

If you save that much your heating bills must be huge or there was an issue with the old boiler or system and/or you have decreased the heat loss.

Not necessarily true John… upgrading the rads for dt20 could easily push the cop up towards 3.5 on most ASHPs. At that cop, you’d be looking a sizeable saving over an 80% efficient gas boiler. Couple in the removal of the standing charge of you don’t cook on gas and there are some good savings to be had.
 

And yes, some people do have large heating bills. We use around 16500kWh of natural gas per 12 months, April-April. I’m sure you’re able to work out how much that will cost at the new rate. ‘Some’ pounds 🤦‍♂️

 

 

 

Edited October 9, 2022 by HughF

[JohnMo]

Gas at 10p is £1650, energy in to house 13200kWh

 

HP at 3.5 CoP 1320/3.5 =3771kWh

 

3771kWh at 34p is £1282.

 

Best part of £400 a year saving

 

 

[SteamyTea]

25 minutes ago, JohnMo said:

Best part of £400 a year saving

Plus the standing charge cost that may be £200 a year now (just guessing as don't have gas and can't be bothered to look it up).

[Ferdinand]

Hmmm.

 

Don't for get that vestigial autumn / winter solar can also effectively boost the CoP for a heat pump.

 

My gas bill reduction solution for the winter is to try a free standing air con / heat pump, and use it the morning for a gentle heat boost. If I need to in due course I could go for a small house battery to help reduce the elec bill to nearly zero.

 

It is on now - spec is delivery of 3.2kW of heat from 1.4kw of power input for a CoP of 2->2.5. My somewhat shaded not yet powerwashed for winter mainly E-facing solar array is delivering something approx. 1 kW at present (total house load including baseload at the heat pump is 450W on the Smart Meter), which means that the effectively CoP is somewhere well above 5.

 

Being rigorous I would need to take lost solar export into account, but these SOTP figures make the point.

 

F

[HughF]

3 hours ago, JohnMo said:

Gas at 10p is £1650, energy in to house 13200kWh

 

HP at 3.5 CoP 1320/3.5 =3771kWh

 

3771kWh at 34p is £1282.

 

Best part of £400 a year saving

 

 

My numbers came out very similar….

[Marvin]

Ours didn't, we used bottled gas for our boiler because we have no mains gas.

[HughF]

18 hours ago, Marvin said:

Ours didn't, we used bottled gas for our boiler because we have no mains gas.

Ouch….