I bought a Heat Pump

Reed_Richards

Mickey666 said:

A litre of heating oil gives about 10kWh of heat and costs about 40p, ie about 4p/kWh

Electricity costs around 14p/kWh or about 3.5 x heating oil.

Therefore, your ASHP has to be around 350% efficient (on average!) just to break even on its running costs.

...

Over the 2 years to the end of November 2020 I paid an average cost of 45.19p per litre of oil.and a litre of oil supposedly gives 10.35 kW.h of heat.  So on average I paid 4.37p per kWh.

My electricity costs 12.374p per kWh (plus standing charge).

So on average I need a COP of 2.83 to break even on running costs.  My heat pump is supposed to achieve better but it won't be hugely better, so yes broadly the same running cost as an oil-fired system.  

I am about to receive my first quarterly RHI payment which will be £352.21.  These will continue for 7 years and should increase a little year-on-year.

If I had stuck with oil I would have had to replace my oil tank immediately and my oil boiler a few years down the road.  I also needed to re-plumb my radiators because the pipes were buried in concrete with no protection and therefore liable to corrode to the point of leaking.  So a fair chunk of the £17,000 is money I would have been obliged to spend anyway, even if I had stuck with oil.  And I'll get a fair bit back over 7 yeas through the RHI payments.        

Reed_Richards

coffeehound said:
I wondered if the efficiency went off a cliff above a certain flow temperature.

My settings do not allow the output temperature to exceed 55 C.  I have the option to boost the cylinder temperature to 60 C once a week as a protection against legionella.  That is the only time the immersion heater is invoked by the heat pump controller, just for the final few degrees.  

shinytop

Mickey666 said:

shinytop said:

Mickey666 said:

Reed_Richards said:

Yesterday was very mild for February, my heat pump consumed 21.4 kWh of electricity in 24 hours.  My total consumption since about 10th December 2020 has been 3456 kWh which works out at 47.4 kWh per day.  My unit rate for electricity is 12.993 p per kWh so my heat pump has cost me £449 in fuel cost so far, an average of £6.16 per day. 

With an oil boiler you get no feel for day-by-day consumption but my average cost per year (over two years) was £920.  This equates to an average energy usage of 59 kWh per day assuming I got 10.35 kWh per litre of heating oil.  The worst case oil usage over December 2018 and January 2019 cost me £4.52 per day.

So so far I an paying more per day to run my heat pump, although as January this year was particularly cold it's not entirely a fair comparison.  I hope I can claw-back the difference over the milder parts of the year, which is what you would expect with a heat pump.   

Those are pretty scary figures! 
Scary for you because you've spent £17,000 installing a system that's more expensive to run than the oil alternative, implying that you'll never get any return on your investment.
Scary for everyone else because fossil fuel prices are only going to increase or be taxed into oblivion so we'll all eventually be paying similar costs to you for heating our homes.
It's not easy, or cheap, being green - though I can't help but feel the early adopters are rather paying through the nose for the privilege.

Nobody said going green was cheap.  Just look at the price of EVs.  Luckily, you and other taxpayers are funding most of my £16k ASHP central heating system installation bill.  And, for me at least, I'll be saving quite a lot vs my old NSH/immersion heater system.   If I could get 65% of the cost of an EV back from the taxpayer I'd have one like a shot.    

Like with ICE cars, we're all going to have to stop burning fossil fuels for heating eventually.  

. . . which is proof of the fundamentally uneconomic technology of ASHP systems.  Anything can be made economically attractive to the consumer if they are given grants to pay for it, and good luck to you, but it doesn't make it a sensible solution in the long term . . . at least not until the general population is lulled into paying 3x, 4x, or more than their current domestic heating costs.

I agree that burning fossil fuels will have to stop eventually, but the costs of the alternatives are going to be a huge shock.  This is why governments the world over are having to give out massive grants and subsidies to smooth the way and, hopefully, prevent rioting in the streets when people cannot afford to heat their homes despite living on an island sitting on top of centuries worth of coal.

RHI is pitched at people like me and @Reed_Richards, who had electric or oil heating.  An ASHP system is not 3-4 times more expensive to run than oil, it's broadly comparable if you use it properly.  The problem is going to be gas, simply because it's currently so cheap. But the millions of GCH systems out there are like the millions of ICE cars.  They are going to have to go and their replacements will more expensive and users will have to make changes to the way they use them.  I agree it's going to be a difficult sell, but the days of having our own personal fossil fuel burning devices are numbered.  I'm not sure if a battery powered barbecue would work though.

Reed_Richards

Cardew said

Most heat pumps operate at a lower temperature than 50C for radiators; I suggest 35C is typical for maximum efficiency.

Is this true?  I doubt it.  I imagine most heat pumps go into new builds.  New builds can incorporate underfloor heating with around 35 C water temperature and this will certainly achieve very good efficiency.  But you'll want radiators in properties that already have radiators or in properties that previously had no central heating (or storage heaters).  You are going to want to fit the new radiators where the old ones were because that is where the pipes go and where you have free wall space without any furniture in the way (this latter consideration would also apply to replacing storage heaters).  Using 50/45 C kept the radiators small enough that I was able to do this in most rooms, anything lower in water temperature and the radiators would have needed such a large surface area that it would have caused problems.  Therefore I would respectfully suggest that a water temperature of around 50 C probably is the norm for heat pumps with radiators.

Edit.  Oh, and the thing I completely forgot to mention is that 50 C is what you need for the middle of winter.  Once the weather warmed up after mid February I reduced the maximum water temperature setting to 40 C using the controller in the living room.  I could do that because if it's not so cold outside the house does not lose heat so fast so I don't need to run my radiators at their full rated output.       

shinytop

A heat pump technical question rather than an existential one.
@Reed_Richards, do you run your HW heating constantly?  Ours was left set up like this after the installation but I'm not sure keeping 250l of water hot 24/7 is the best solution.  Pre-ASHP we had the immersion set for a couple of hours at night and that was enough.  Any thoughts?

Reed_Richards

I have hot water heating on from 6 am to 10 pm.  At the moment I am working out how to best co-ordinate with my solar panels.  I am trying 50 C cylinder temperature from 6 am to 10 am to make sure we have enough hot water for morning showers.  My controller allows the water temperature to get down to about 42 C if the nominal temperature is 50 C before it bothers to re-heat the cylinder.  Then 40 C nominal (so potentially as low as 32 C) from 10 am to 4 pm during which time I try to make the water as hot as I can using the immersion heater and spare solar electricity.  Then back to 50 C after 4 pm in case it was cloudy and I didn't manage to make use of the immersion heater.  I am using the immersion heater because its 3 kW demand is better matched to the output of my solar panels; the heat pump uses a short burst of high power to heat the water.  On a good day it will take the cylinder up to about 80 C which then lasts to the following day.     

Martyn1981

shinytop said:

Mickey666 said:

shinytop said:

Mickey666 said:

Reed_Richards said:

Yesterday was very mild for February, my heat pump consumed 21.4 kWh of electricity in 24 hours.  My total consumption since about 10th December 2020 has been 3456 kWh which works out at 47.4 kWh per day.  My unit rate for electricity is 12.993 p per kWh so my heat pump has cost me £449 in fuel cost so far, an average of £6.16 per day. 

With an oil boiler you get no feel for day-by-day consumption but my average cost per year (over two years) was £920.  This equates to an average energy usage of 59 kWh per day assuming I got 10.35 kWh per litre of heating oil.  The worst case oil usage over December 2018 and January 2019 cost me £4.52 per day.

So so far I an paying more per day to run my heat pump, although as January this year was particularly cold it's not entirely a fair comparison.  I hope I can claw-back the difference over the milder parts of the year, which is what you would expect with a heat pump.   

Those are pretty scary figures! 
Scary for you because you've spent £17,000 installing a system that's more expensive to run than the oil alternative, implying that you'll never get any return on your investment.
Scary for everyone else because fossil fuel prices are only going to increase or be taxed into oblivion so we'll all eventually be paying similar costs to you for heating our homes.
It's not easy, or cheap, being green - though I can't help but feel the early adopters are rather paying through the nose for the privilege.

Nobody said going green was cheap.  Just look at the price of EVs.  Luckily, you and other taxpayers are funding most of my £16k ASHP central heating system installation bill.  And, for me at least, I'll be saving quite a lot vs my old NSH/immersion heater system.   If I could get 65% of the cost of an EV back from the taxpayer I'd have one like a shot.    

Like with ICE cars, we're all going to have to stop burning fossil fuels for heating eventually.  

. . . which is proof of the fundamentally uneconomic technology of ASHP systems.  Anything can be made economically attractive to the consumer if they are given grants to pay for it, and good luck to you, but it doesn't make it a sensible solution in the long term . . . at least not until the general population is lulled into paying 3x, 4x, or more than their current domestic heating costs.

I agree that burning fossil fuels will have to stop eventually, but the costs of the alternatives are going to be a huge shock.  This is why governments the world over are having to give out massive grants and subsidies to smooth the way and, hopefully, prevent rioting in the streets when people cannot afford to heat their homes despite living on an island sitting on top of centuries worth of coal.

RHI is pitched at people like me and @Reed_Richards, who had electric or oil heating.  An ASHP system is not 3-4 times more expensive to run than oil, it's broadly comparable if you use it properly.  The problem is going to be gas, simply because it's currently so cheap. But the millions of GCH systems out there are like the millions of ICE cars.  They are going to have to go and their replacements will more expensive and users will have to make changes to the way they use them.  I agree it's going to be a difficult sell, but the days of having our own personal fossil fuel burning devices are numbered.  I'm not sure if a battery powered barbecue would work though.

Spot on. And the cost benefits of heat pumps are (or can) be even higher if we consider:
1. The externality costs of FF burning, which are often ignored in simple cost comparisons, but will become more significant as carbon prices rise to reflect the real costs.
2. The use of cheap rate leccy can reduce the costs significantly, and through the winter provide an excellent demand for wind generation. I'd have thought 10p/kWh was a sensible upper figure for E7 rates, with many paying much less.
3. PV - goes without saying really. We can't produce our own oil or gas cheaply, but we can generate our own leccy, and whilst its contribution in the worst 3 heating months will be small, it can provide a significant amount (perhaps even all) heating for the 'better' 4 heating months (Mch, Apr, Sep & Oct), plus of course all DHW for the warmer 9(ish) months.
4. On a personal level, you can even consider investing in some RE generation schemes to meet your leccy demand on a net basis, thereby taking some personal responsibility ....... and having fun.

shinytop

Reed_Richards said:

I have hot water heating on from 6 am to 10 pm.  At the moment I am working out how to best co-ordinate with my solar panels.  I am trying 50 C cylinder temperature from 6 am to 10 am to make sure we have enough hot water for morning showers.  My controller allows the water temperature to get down to about 42 C if the nominal temperature is 50 C before it bothers to re-heat the cylinder.  Then 40 C nominal (so potentially as low as 32 C) from 10 am to 4 pm during which time I try to make the water as hot as I can using the immersion heater and spare solar electricity.  Then back to 50 C after 4 pm in case it was cloudy and I didn't manage to make use of the immersion heater.  I am using the immersion heater because its 3 kW demand is better matched to the output of my solar panels; the heat pump uses a short burst of high power to heat the water.  On a good day it will take the cylinder up to about 80 C which then lasts to the following day.     

Different for me at the moment as I don't have solar.  I'm currently on a decent E7 rate so HW at night will be better for me.  Whether that's a few hours of the ASHP or a shorter blast of immersion is something I'll have to work out; it may depend on the outside temperature.  Must look into solar next.

Mickey666

Reed_Richards said:

Mickey666 said:

A litre of heating oil gives about 10kWh of heat and costs about 40p, ie about 4p/kWh

Electricity costs around 14p/kWh or about 3.5 x heating oil.

Therefore, your ASHP has to be around 350% efficient (on average!) just to break even on its running costs.

...

Over the 2 years to the end of November 2020 I paid an average cost of 45.19p per litre of oil.and a litre of oil supposedly gives 10.35 kW.h of heat.  So on average I paid 4.37p per kWh.

My electricity costs 12.374p per kWh (plus standing charge).

So on average I need a COP of 2.83 to break even on running costs.  My heat pump is supposed to achieve better but it won't be hugely better, so yes broadly the same running cost as an oil-fired system.  

I am about to receive my first quarterly RHI payment which will be £352.21.  These will continue for 7 years and should increase a little year-on-year.

If I had stuck with oil I would have had to replace my oil tank immediately and my oil boiler a few years down the road.  I also needed to re-plumb my radiators because the pipes were buried in concrete with no protection and therefore liable to corrode to the point of leaking.  So a fair chunk of the £17,000 is money I would have been obliged to spend anyway, even if I had stuck with oil.  And I'll get a fair bit back over 7 yeas through the RHI payments.        

Thanks for the updated figures and confirmation that the running costs of oil and ASHP are broadly the same.

The RHI subsidy will help of course, but even at £1500 per year over seven years that's only £10.5k of the £17k capital outlay, and that's without even considering the potential investment return on teh £17k if it hadn't been spent on the ASHP.

So, all in all, your home heating bill cost is going to be greater than an equivalent oil-fired system

Don't get me wrong though, I'm not some anti-green climate change denialist.  Indeed, my view tends toward the apocalyptic in the sense that humanity is over-running the planet's capability to sustain us and that much of these 'green initiatives' are akin to rearranging the chairs on the Titanic.  I appreciate that other views are available

When I moved to my current house about 13 years ago it required a great deal of renovation work including completely new heating and DHW systems.  I was very keen to 'go green' and investigated various options from wood pellets, biomass, GSHP, as well as solar thermal and PV.  I even investigated fast-rotation coppicing to grow my own wood chips as I'm fortunate to have sufficient acreage to support such a scheme.  But all of them failed the basic economic viability tests.  Then I discovered our village has mains gas and I could get a new connection for £300 and the game was over! 

I don't discount the possibility of eventually swapping out my gas boiler in the decades to come but at least my extensive use of 'wet' UFH should help convert to a future system based on ASHP or similar where the output temperatures are lower.  But, for the time being, I can see no economic rationale to make costly capital investments in greener technology, even with government handouts to lessen the higher costs.

Mickey666

Martyn1981 said:

shinytop said:

Mickey666 said:

shinytop said:

Mickey666 said:

Reed_Richards said:

Yesterday was very mild for February, my heat pump consumed 21.4 kWh of electricity in 24 hours.  My total consumption since about 10th December 2020 has been 3456 kWh which works out at 47.4 kWh per day.  My unit rate for electricity is 12.993 p per kWh so my heat pump has cost me £449 in fuel cost so far, an average of £6.16 per day. 

With an oil boiler you get no feel for day-by-day consumption but my average cost per year (over two years) was £920.  This equates to an average energy usage of 59 kWh per day assuming I got 10.35 kWh per litre of heating oil.  The worst case oil usage over December 2018 and January 2019 cost me £4.52 per day.

So so far I an paying more per day to run my heat pump, although as January this year was particularly cold it's not entirely a fair comparison.  I hope I can claw-back the difference over the milder parts of the year, which is what you would expect with a heat pump.   

Those are pretty scary figures! 
Scary for you because you've spent £17,000 installing a system that's more expensive to run than the oil alternative, implying that you'll never get any return on your investment.
Scary for everyone else because fossil fuel prices are only going to increase or be taxed into oblivion so we'll all eventually be paying similar costs to you for heating our homes.
It's not easy, or cheap, being green - though I can't help but feel the early adopters are rather paying through the nose for the privilege.

Nobody said going green was cheap.  Just look at the price of EVs.  Luckily, you and other taxpayers are funding most of my £16k ASHP central heating system installation bill.  And, for me at least, I'll be saving quite a lot vs my old NSH/immersion heater system.   If I could get 65% of the cost of an EV back from the taxpayer I'd have one like a shot.    

Like with ICE cars, we're all going to have to stop burning fossil fuels for heating eventually.  

. . . which is proof of the fundamentally uneconomic technology of ASHP systems.  Anything can be made economically attractive to the consumer if they are given grants to pay for it, and good luck to you, but it doesn't make it a sensible solution in the long term . . . at least not until the general population is lulled into paying 3x, 4x, or more than their current domestic heating costs.

I agree that burning fossil fuels will have to stop eventually, but the costs of the alternatives are going to be a huge shock.  This is why governments the world over are having to give out massive grants and subsidies to smooth the way and, hopefully, prevent rioting in the streets when people cannot afford to heat their homes despite living on an island sitting on top of centuries worth of coal.

RHI is pitched at people like me and @Reed_Richards, who had electric or oil heating.  An ASHP system is not 3-4 times more expensive to run than oil, it's broadly comparable if you use it properly.  The problem is going to be gas, simply because it's currently so cheap. But the millions of GCH systems out there are like the millions of ICE cars.  They are going to have to go and their replacements will more expensive and users will have to make changes to the way they use them.  I agree it's going to be a difficult sell, but the days of having our own personal fossil fuel burning devices are numbered.  I'm not sure if a battery powered barbecue would work though.

Spot on. And the cost benefits of heat pumps are (or can) be even higher if we consider:
1. The externality costs of FF burning, which are often ignored in simple cost comparisons, but will become more significant as carbon prices rise to reflect the real costs.

Not forgetting the reduction/removal of government subsidies that currently hide the real costs of heat pumps

2. The use of cheap rate leccy can reduce the costs significantly, and through the winter provide an excellent demand for wind generation. I'd have thought 10p/kWh was a sensible upper figure for E7 rates, with many paying much less.

Though of course the daytime rates will consequently be higher so unless you only want to heat your home through the night the overall costs may not be reduced very much, indeed it's possible they would be increased.

3. PV - goes without saying really. We can't produce our own oil or gas cheaply, but we can generate our own leccy, and whilst its contribution in the worst 3 heating months will be small, it can provide a significant amount (perhaps even all) heating for the 'better' 4 heating months (Mch, Apr, Sep & Oct), plus of course all DHW for the warmer 9(ish) months.

4. On a personal level, you can even consider investing in some RE generation schemes to meet your leccy demand on a net basis, thereby taking some personal responsibility ....... and having fun.

4 - 'having fun' seems to be a significant driver for these 'green' technologies, or 'alternative technology' as they used to be called.  And I agree.  It's certainly what switched me on to investigating such things and playing around with old radiators, pumps, pipework to experiment solar thermal panels and programming microcontrollers to measure, control and calculate energy flows.  It IS fun, trying to capture useful energy for free . . . except that it isn't 'free' at all and when I took off my 'fun' hat and looked into the hard economic realities of installing and running such systems in a practical domestic environment, they didn't pass the test.  The very fact that government subsidies are needed to persuade most people to make such choices is proof of that.

Of course, the economics will likely change (or be more widely manipulated by taxes and subsidies) in the coming decades, but in the meantime, apart from 'having fun' there seems little financial incentive for these 'alternative' technologies and the early adopters, as ever, will be the ones paying the high price.