The move to heat pumps

shinytop

Cardew said:

QrizB said:

As Reed_Richards said upthread, his experience with a heat pump is that a more realistic COP is ~3, not the 2.2 that the OP assumed. With a COP of 3, the calculation becomes:

Replaced with 300% efficient air source electric heat pump. Average cost of electricity 14.37p/kWh. Annual bill = (25,000 x 14.47)/3 = £1206/yr

So the increase in cost is more like 15%, not 50%.

"How is the government planning to make this work?" Well that's really a question for BEIS, not me, but as a random person typing on the internet I would imagine a combination of:

1. Increased taxes on gas (and on FF generally).
2. Subsidies for installation of green domestic heating systems and for related energy efficiency measures in existing properties.
3. Increased benefit payments to reduce fuel poverty in low income households.
4. Changes to building regs to make new-builds and refurbs more energy efficient.

I'm not claiming any of these steps are new or imaginative, just things that government has done in the past, is doing now and could continue to do in the future.

In the OP's specific case, adding a penny to a kWh of gas (so 3.8p/kWh becomes 4.8p/kWh) would increase the annual cost of the gas heated house to £1333/yr and so the HP system would now be cheaper to run.

A couple of points on the price assumptions above.

I have just looked for the cheapest price NOW available for 25,000kWh in my area(West Midlands). The cheapest electricity only tariff is now 17.281p/kWh + 22p DSC (I currently pay 13.48p/kWh)

The cheapest gas for a dual fuel is now 3.25p/kWh + 22.26p DSC (gas only is more expensive) (I currently pay 2.37p/kWh)

So the cost for 25,000kWh electricity is £4,320 assuming a system COP of 3.0* that is £1,440.

The cost of 25,000kWh gas is £812 + £81 DSC = £893.

Note. The DSC for electricity will need to be paid for both systems so are not included.

So by my calculations using the prices above a heat pump will cost £547 more than gas, an increase of 61.2%.

* Whilst a COP of 3.0 is achievable, for many homes it is not. See:

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/606818/DECC_RHPP_161214_Final_Report_v1-13.pdf

 

‘Overall conclusions

The  analysis  presented  here  demonstrates  that  median  SPFH2  values  for  ASHP  and  GSHP  in  the cropped B2 sample are around 2.65 and  2.81 respectively. Approximately two thirds of ASHP and four fifths  of GSHP  in the  cropped  B2  sample  met  the EU  criterion  for  being  considered  “renewable”.Filtering the data in alternative but equally plausible ways results in similar conclusions.’

There is the added factor that with gas CH people who are out all day can have the heating off all day, and at night,  and have it timed to come on, say, 30 mins before they return/get up.

This is not possible with an ASHP with lower water temperatures, albeit it can be set back a degree or two.

Does a larger, cooler but correctly sized radiator heat up a room slower than a smaller, hotter one with the same power output?  Also, I have my ASHP thermostats on timers and the radiators seem to heat up as quickly as the gas CH ones in my old house (although I haven't measured them).  

Baxter100

The efficiency of the heat pump is the crux of the matter. Can efficiencies of 300% be achieved with an ASHP/rads system? Yes, with a perfect set of circumstances. If we could rip out all 22 million gas/oil/LPG boilers and do a straight swap for ASHPs that operate at an efficiency of 300% over their lifetime then with a bit of tinkering on gas and electric prices the government could get this to work.

In reality however the operating efficiency of an ASHP can vary anywhere between 120-320% depending on a whole raft of factors:

- Temperature differential

- Location of the heat pump

- Size of the heat pump

- Type and size of the emitter

- Quality of the installation

- Design flow temperature

- Overall heating requirements

- Domestic hot water requirements

- Energy consumption from pumps and auxiliary sources

And so on and so on. Every property and installation will be different. It's like selling someone a gas boiler and telling them that the efficiency could be anywhere between 30 and 90%.

In order for this to work all 22 million dwellings would need a thorough pre and post assessment to look at all of the above factors and determine how to install a heat pump to work at maximum potential efficiency. In reality Bob the plumber who has taken a two week training course on heat pumps will turn up, rip out the existing boiler and stick in a heat pump in its place.

Reed_Richards

shinytop said:
Does a larger, cooler but correctly sized radiator heat up a room slower than a smaller, hotter one with the same power output?  Also, I have my ASHP thermostats on timers and the radiators seem to heat up as quickly as the gas CH ones in my old house (although I haven't measured them).  

Once you're at the designed operating temperature obviously all "correctly-sized" radiators are equal.  But:

• I did a calculation on my old radiators assuming they were intended to operate at delta T = 50. They would have given about 30% more output compared to my new ones, which were specified using some very detailed calculations to be the "correct" size.
• Way back in 1998 I replaced an ancient oil boiler with a condensing gas boiler.  My radiators were probably sized for a higher delta T than I ran the gas boiler at and that house never warmed up very quickly.
• Heat pumps try to maintain a differential between the flow and return temperature, I believe.  And they are not over-sized as a gas boiler almost inevitably is so probably gas will heat your water faster.
• On the other hand gas has to get the water hotter to reach the specified operating temperature so there is a trade-off.

The moral, to my way of thinking, is that you should not believe heat pumps are slow to heat up a house until you have talked to some people who have heat pumps with radiators and are therefore in a position to know.

       

Reed_Richards

Baxter100 said:In reality Bob the plumber who has taken a two week training course on heat pumps will turn up, rip out the existing boiler and stick in a heat pump in its place.

At the moment if you want the RHI payments you need an MCS accredited installer.  They use a software package that does a very detailed heat loss calculation, works out the required size (i.e. output) of the radiators room-by-room with the operating temperature as an input to the calculation and thus the size of the heat pump required.  This is far more rigorous than anything a typical plumber installing a fossil fuel boiler would do.

Actually installing the heat pump is mostly straightforward plumbing and ancillary electricals.  There aren't many people doing heat pump installations so they get plenty of on-the-job training after the course.  Better get your heat pump in quick before it comes down to a large number of less well-trained workmen doing the job (and the RHI payments are abolished).           

Baxter100

Well yes, exactly. At the moment it is a comparatively niche and expensive market. As and when they are installing millions of heat pumps each year it will be very far from that.

Especially if the government will be subsidising the installation costs to a large degree. Anyone who has any experience of ECO or similar will know that these schemes typically end up as a race to the bottom.

shinytop

Baxter100 said:

The efficiency of the heat pump is the crux of the matter. Can efficiencies of 300% be achieved with an ASHP/rads system? Yes, with a perfect set of circumstances. If we could rip out all 22 million gas/oil/LPG boilers and do a straight swap for ASHPs that operate at an efficiency of 300% over their lifetime then with a bit of tinkering on gas and electric prices the government could get this to work.

In reality however the operating efficiency of an ASHP can vary anywhere between 120-320% depending on a whole raft of factors:

- Temperature differential

- Location of the heat pump

- Size of the heat pump

- Type and size of the emitter

- Quality of the installation

- Design flow temperature

- Overall heating requirements

- Domestic hot water requirements

- Energy consumption from pumps and auxiliary sources

And so on and so on. Every property and installation will be different. It's like selling someone a gas boiler and telling them that the efficiency could be anywhere between 30 and 90%.

In order for this to work all 22 million dwellings would need a thorough pre and post assessment to look at all of the above factors and determine how to install a heat pump to work at maximum potential efficiency. In reality Bob the plumber who has taken a two week training course on heat pumps will turn up, rip out the existing boiler and stick in a heat pump in its place.

And the two items I have highlighted make a massive difference.  In fact they make a difference to a gas heating/HW systems but gas is so cheap nobody bothers.  People have become used to a constant 21/22 degrees indoors in all seasons and having deep baths and/or 20 minute showers.  That's a relatively recent thing and If they want this in the future it's going to cost them a lot. The alternative is 18-19 deg and a jumper and 5 minute showers.  Lower temps are perfectly fine for all (including babies/children), except the sick and very elderly, who can be helped financially.  

Most modern ASHPs can deliver a COP of 2.5-3 in real (not test) conditions.    

shinytop

Cardew said:

QrizB said:

As Reed_Richards said upthread, his experience with a heat pump is that a more realistic COP is ~3, not the 2.2 that the OP assumed. With a COP of 3, the calculation becomes:

Replaced with 300% efficient air source electric heat pump. Average cost of electricity 14.37p/kWh. Annual bill = (25,000 x 14.47)/3 = £1206/yr

So the increase in cost is more like 15%, not 50%.

"How is the government planning to make this work?" Well that's really a question for BEIS, not me, but as a random person typing on the internet I would imagine a combination of:

1. Increased taxes on gas (and on FF generally).
2. Subsidies for installation of green domestic heating systems and for related energy efficiency measures in existing properties.
3. Increased benefit payments to reduce fuel poverty in low income households.
4. Changes to building regs to make new-builds and refurbs more energy efficient.

I'm not claiming any of these steps are new or imaginative, just things that government has done in the past, is doing now and could continue to do in the future.

In the OP's specific case, adding a penny to a kWh of gas (so 3.8p/kWh becomes 4.8p/kWh) would increase the annual cost of the gas heated house to £1333/yr and so the HP system would now be cheaper to run.

A couple of points on the price assumptions above.

I have just looked for the cheapest price NOW available for 25,000kWh in my area(West Midlands). The cheapest electricity only tariff is now 17.281p/kWh + 22p DSC (I currently pay 13.48p/kWh)

The cheapest gas for a dual fuel is now 3.25p/kWh + 22.26p DSC (gas only is more expensive) (I currently pay 2.37p/kWh)

So the cost for 25,000kWh electricity is £4,320 assuming a system COP of 3.0* that is £1,440.

The cost of 25,000kWh gas is £812 + £81 DSC = £893.

Note. The DSC for electricity will need to be paid for both systems so are not included.

So by my calculations using the prices above a heat pump will cost £547 more than gas, an increase of 61.2%.

* Whilst a COP of 3.0 is achievable, for many homes it is not. See:

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/606818/DECC_RHPP_161214_Final_Report_v1-13.pdf

 

‘Overall conclusions

The  analysis  presented  here  demonstrates  that  median  SPFH2  values  for  ASHP  and  GSHP  in  the cropped B2 sample are around 2.65 and  2.81 respectively. Approximately two thirds of ASHP and four fifths  of GSHP  in the  cropped  B2  sample  met  the EU  criterion  for  being  considered  “renewable”.Filtering the data in alternative but equally plausible ways results in similar conclusions.’

There is the added factor that with gas CH people who are out all day can have the heating off all day, and at night,  and have it timed to come on, say, 30 mins before they return/get up.

This is not possible with an ASHP with lower water temperatures, albeit it can be set back a degree or two.

I wonder why your area is so expensive?  I tried a random Solihull postcode and I got Symbio offering 11.799 and 24p/day.  Your 17.28 isn't far off the BG standard variable rate.  

Baxter100

shinytop said:

Baxter100 said:

The efficiency of the heat pump is the crux of the matter. Can efficiencies of 300% be achieved with an ASHP/rads system? Yes, with a perfect set of circumstances. If we could rip out all 22 million gas/oil/LPG boilers and do a straight swap for ASHPs that operate at an efficiency of 300% over their lifetime then with a bit of tinkering on gas and electric prices the government could get this to work.

In reality however the operating efficiency of an ASHP can vary anywhere between 120-320% depending on a whole raft of factors:

- Temperature differential

- Location of the heat pump

- Size of the heat pump

- Type and size of the emitter

- Quality of the installation

- Design flow temperature

- Overall heating requirements

- Domestic hot water requirements

- Energy consumption from pumps and auxiliary sources

And so on and so on. Every property and installation will be different. It's like selling someone a gas boiler and telling them that the efficiency could be anywhere between 30 and 90%.

In order for this to work all 22 million dwellings would need a thorough pre and post assessment to look at all of the above factors and determine how to install a heat pump to work at maximum potential efficiency. In reality Bob the plumber who has taken a two week training course on heat pumps will turn up, rip out the existing boiler and stick in a heat pump in its place.

And the two items I have highlighted make a massive difference.  In fact they make a difference to a gas heating/HW systems but gas is so cheap nobody bothers.  People have become used to a constant 21/22 degrees indoors in all seasons and having deep baths and/or 20 minute showers.  That's a relatively recent thing and If they want this in the future it's going to cost them a lot. The alternative is 18-19 deg and a jumper and 5 minute showers.  Lower temps are perfectly fine for all (including babies/children), except the sick and very elderly, who can be helped financially.  

Most modern ASHPs can delivering a COP of 2.5-3 in real (not test) conditions.    

I agree. But good luck to the government in trying to convince people that they should accept a lower standard of living.

Cardew

shinytop said:

I wonder why your area is so expensive?  I tried a random Solihull postcode and I got Symbio offering 11.799 and 24p/day.  Your 17.28 isn't far off the BG standard variable rate.  

Sorry my mistake! You are correct.

I used Energyhelpline.com as I normally do, but the default setting had been changed to 'only list those who we can switch you to' instead of 'list all companies'; and those were the prices they listed. After changing the settings, Symbio were not listed but there were a couple of variable tariffs about 12.3p/kWh. The cheapest fixed tariff was 14.774p/kWh and all of the 'Big 6' were 17p+.

most companies including the Big 6 Gas had about 3.2p-3.3p/kWh; still considerably lower than the OP's 3.8p/kWh

Hanging my head in shame!

EVandPV

Half price heat pumps and '£4,000 grants' to help households before gas boiler ban in 2025

https://www.dailyrecord.co.uk/lifestyle/money/household-help-gas-boiler-ban-24220477.amp