People Saying Heat Pumps are Rubbish - Are They?

QrizB

benson1980 said:

hairydog said:

2. Electricity costs four times as much as mains gas, so unless the COP averages well over 4, running costs will be higher. COP's always worst in cold weather when you use most heating.

No boiler is 100% efficient. Thus an ASHP does not need to be more than 400% efficient to just break even. The SCOP is the important figure when projecting costs/savings over the course of a year and anything around 3.8 will likely be similar cost to gas or potentially provide a small saving.

Also a lot of gas boilers don't actually achieve their 90+% effiency, and getting to that effiency will often need the same sort of radiator replacements that come with a heat pump. Any HP COP better than 3 is likely to be cost competitive.

Spoonie_Turtle

Plus any non-SVT tariffs that can get your average unit rate lower than the SVT can mean a lower COP will still save money.  (But obviously such tariffs are not as bankable in the long term, as suppliers can change and withdraw them at their discretion.)

benson1980

QrizB said:

benson1980 said:

hairydog said:

2. Electricity costs four times as much as mains gas, so unless the COP averages well over 4, running costs will be higher. COP's always worst in cold weather when you use most heating.

No boiler is 100% efficient. Thus an ASHP does not need to be more than 400% efficient to just break even. The SCOP is the important figure when projecting costs/savings over the course of a year and anything around 3.8 will likely be similar cost to gas or potentially provide a small saving.

Also a lot of gas boilers don't actually achieve their 90+% effiency, and getting to that effiency will often need the same sort of radiator replacements that come with a heat pump. Any HP COP better than 3 is likely to be cost competitive.

Yes wouldn't necessarily disagree. Ours in January averaged around 3.2 and as said was probably around 10% more expensive versus gas the previous year but....this was for a much more consistently warm house. Just didn't get where the "must have a SCOP of well above 4" came from really. We're on track for around 3.8 ish I think and that would definitely give us a saving (not taking into account solar or battery- taking those into account the savings are significant).

NedS

QrizB said:

benson1980 said:

hairydog said:

2. Electricity costs four times as much as mains gas, so unless the COP averages well over 4, running costs will be higher. COP's always worst in cold weather when you use most heating.

No boiler is 100% efficient. Thus an ASHP does not need to be more than 400% efficient to just break even. The SCOP is the important figure when projecting costs/savings over the course of a year and anything around 3.8 will likely be similar cost to gas or potentially provide a small saving.

Also a lot of gas boilers don't actually achieve their 90+% effiency, and getting to that effiency will often need the same sort of radiator replacements that come with a heat pump. Any HP COP better than 3 is likely to be cost competitive.

Further, whilst Ofgem cap prices for electricity may be ~4 times that of gas, many of us with an ASHP are on cheaper tariffs and pay significantly less for our electricity. Such tariffs are not available for gas AFAIK.

Additionally, we had a solar array installed at the same time as our ASHP. In the first year, our solar has produced more kWh of electricity than our ASHP has consumed, so our heating and DHW is completely offset by our solar generation. Gas fired heating has no such self-generation options, you are always going to be buying gas at the market rate.

I averaged an import price of 19.7p during January (our coldest month) with a COP of 3.95, giving a cost per kWh of 4.99p, significantly cheaper than the cost of gas at 6.54p, before allowing for the 85-90% efficiency of a gas boiler. That's our worst case, warmer months are significantly cheaper as the COP improves.

Spies

NedS said:

I averaged an import price of 19.7p during January (our coldest month) with a COP of 3.95, giving a cost per kWh of 4.99p, significantly cheaper than the cost of gas at 6.54p, before allowing for the 85-90% efficiency of a gas boiler. That's our worst case, warmer months are significantly cheaper as the COP improves.

For January I was 16.38p/kWh and only 2.93 SCOP but I don't really care because the house has been way more comfortable than it ever was with gas central heating

So for this month solar has pretty much been covering any heat pump usage from around 8am to 5pm

NedS

Spies said:

NedS said:

I averaged an import price of 19.7p during January (our coldest month) with a COP of 3.95, giving a cost per kWh of 4.99p, significantly cheaper than the cost of gas at 6.54p, before allowing for the 85-90% efficiency of a gas boiler. That's our worst case, warmer months are significantly cheaper as the COP improves.

For January I was 16.38p/kWh and only 2.93 SCOP but I don't really care because the house has been way more comfortable than it ever was with gas central heating

So for this month solar has pretty much been covering any heat pump usage from around 8am to 5pm

Yes, we keep our house at around 19-20C and can achieve this with flow temps of 30-32C which no doubt contributes to our SCOP in winter. On the very coldest day of the year, our COP was fractionally above 3 making costs comparable to gas under those worst case conditions.

Reed_Richards

NedS said:

Spies said:

NedS said:

I averaged an import price of 19.7p during January (our coldest month) with a COP of 3.95, giving a cost per kWh of 4.99p, significantly cheaper than the cost of gas at 6.54p, before allowing for the 85-90% efficiency of a gas boiler. That's our worst case, warmer months are significantly cheaper as the COP improves.

For January I was 16.38p/kWh and only 2.93 SCOP but I don't really care because the house has been way more comfortable than it ever was with gas central heating

So for this month solar has pretty much been covering any heat pump usage from around 8am to 5pm

Yes, we keep our house at around 19-20C and can achieve this with flow temps of 30-32C which no doubt contributes to our SCOP in winter. On the very coldest day of the year, our COP was fractionally above 3 making costs comparable to gas under those worst case conditions.

Does the temperature at which you keep your house matter with regard to a comparison?  If you always kept your house at 19-20 C then that would have cut your gas cost before and your electricity costs after.  

Spies

Reed_Richards said:

NedS said:

Spies said:

NedS said:

I averaged an import price of 19.7p during January (our coldest month) with a COP of 3.95, giving a cost per kWh of 4.99p, significantly cheaper than the cost of gas at 6.54p, before allowing for the 85-90% efficiency of a gas boiler. That's our worst case, warmer months are significantly cheaper as the COP improves.

For January I was 16.38p/kWh and only 2.93 SCOP but I don't really care because the house has been way more comfortable than it ever was with gas central heating

So for this month solar has pretty much been covering any heat pump usage from around 8am to 5pm

Yes, we keep our house at around 19-20C and can achieve this with flow temps of 30-32C which no doubt contributes to our SCOP in winter. On the very coldest day of the year, our COP was fractionally above 3 making costs comparable to gas under those worst case conditions.

Does the temperature at which you keep your house matter with regard to a comparison?  If you always kept your house at 19-20 C then that would have cut your gas cost before and your electricity costs after.  

20c with a heatpump feels very different to that of using gas CH, I think the constant cycling of the radiators on and off made quite intense convex currents which made me feel like there's a cold draught over you, also I ran my gas CH at the lowest flow temp to get condensing, I did try running the gas CH on low and slow but it cost me a fortune

Alnat1

Spies said:

20c with a heatpump feels very different to that of using gas CH, I think the constant cycling of the radiators on and off made quite intense convex currents which made me feel like there's a cold draught over you, also I ran my gas CH at the lowest flow temp to get condensing, I did try running the gas CH on low and slow but it cost me a fortune

Much easier to get the radiators properly balanced with a heat pump too. The heat is very gentle and even, no hot end and cold end of a room. Our bedrooms are 18C (doors closed) and the rest of the house is 20C day, 18C overnight. It just works, always comfortable and makes me happy 

BoYaNY73

matt_drummer said:

sohekim said:

I live between 2 houses that both have Air Source Heat Pumps fitted and both of them exceed the sound pressure levels. The Law states they must be 42dB or less and there is a good reason for this but we have recorded both units running at over 70dB. The manufactures do sound level tests but these I have found out to be flawed as they quote a "free field" test sound level which means that during the test there are no reflective surfaces for sounds to bounce off and the unit is basically clear of any obstructions and they manufactures do not have to record lower frequencies.  Nor do they take into account that rural village sound levels are lower than 40dB during the night so when calculations are made the manufacture uses the urban sound levels instead However these units when running emit deep frequency hums that can disturb the sleep. Also the colder or lower atmospheric pressure is the longer the Air Source Heat Pumps run for.  They can be a nuisance for people living near to them. At night prior to the fitting of the ASHP the sound level at night was 29.2dB but now it is between 60db and 75db when they are running and it is agony at night. All measurements have been taken using professional equipment and you can see there is a big difference between the normal quiet village life and when the ASHP's are running. It is so easy for these units to cause health problems as the sound grinds a person down. 

I don't believe you, sorry.

Next door’s fans from their air conditioners are driving me crazy! They certainly grind you down ! I feel the only thing to do is sell up and move house.