I bought a Heat Pump

shinytop

@Reed_Richards

It's hard to compare because it's two different houses on different days in different places.  In that sample, I'm using 2.8kW max and you're around 4.2kW max. We don't know how much power is being delivered, just consumed.  We don't know what our respective  COPS were, how cold it was (3 degrees for me). But I'm only raising the flow by 4-5 degrees and you're raising it by 10.  Mine will raise the power input up to more than 6kW if it has to raise the flow a lot, e.g after it's been off all night or if it's very cold. 

Without knowing how the control system works and what sort of feedback loop it has it's hard to say what's going on.  I wonder if Mitsubishi would tell me if I asked?  

Very interesting anyway. 

Reed_Richards

Now that my heat pump has gone to bed for the night I can see that my average consumption for January was 26.9 kWh per day.

This compares to 29.8  kWh per day in December.

I don't have an exact figure for January 2021 but my average from 30/12/20 to 28/1/21 was 50.3 kWh per day.  

Verdigris

That's a significant reduction. Your fiddling hasn't been in vain! Well done. I don't recall last winter being particularly cold, so I hope that is mostly a result of fine-tuning, rather than the serendipity of the weather.

Reed_Richards

My original weather compensation stopped if the temperature was below 5 C (currently revised to -4 C).  The settings were the ones recommended by the supplier to my installer so did not take the particular circumstances of my house into account.  But I guess that must be generally true of weather compensation; you get the settings you are given.  However with a heat pump, it's a lot more important to get the weather compensation exactly right than it is with a conventional boiler.  

shinytop

Reed_Richards said:

Now that my heat pump has gone to bed for the night I can see that my average consumption for January was 26.9 kWh per day.

This compares to 29.8  kWh per day in December.

I don't have an exact figure for January 2021 but my average from 30/12/20 to 28/1/21 was 50.3 kWh per day.  

That's a great result and even if last year were warmer, it wouldn't make that much difference.  The way your supplier left it you  had a near fixed flow around the average winter temperature.  I think they do that to stop people calling them back.  The customer has nice hot radiators and a warm house and they (the supplier) don't have to pay the electricity bill.

My January 2022 was 30.3 kWh per day.  

EDIT - if only people with gas CH could be bothered to make their heating systems more efficient too.  With gas at 2p per kWh it wasn't worth the effort. Maybe the next price rise will give them an incentive.  

matelodave

I dont know where you chaps live but here is the weekly degree day info for both last year and this year which suggests that where I live in Cambridgeshire last year was colder than this year 
(Data derived from RAF Marham in Norfolk which is the nearest source of met data to me - reading are for Monday mornings)

2021         2022
98             49       First week includes a bit of December so Jan figures are for 35 days
102           84
91             86
68             90
82             72

Totals
441           381

My total leccy consumption was1366kwh in Jan 2021 and 1161kwh in 2022 however  it's not easy to pull out just the heatpump consumption as mine doesn't have a meter, but, at a guess (based on my monthly summer consumption of around 300kwh) last years heating was 1066kwh (1066/35 = 35kwh a day) and this year was 861kwh/35 = 24.6kwh a day

It does seem as though I've used less leccy than perhaps the degree day info would suggest if you assumed that the energy consumption v temp was linear but I'm guessing that if  its not quite as cold then the heatpump efficiency improves, especially if you've got weather compensation activated.

Meatballs

Reed_Richards said:

I have tried degreedays.net and it  makes very little sense to me.  Instead of giving you the basic information, which is the average temperature for any particular day, it obscures that information by telling you days that were warmer than some specified temperature.  I'm sure in some specialised contexts this is useful but I do not find it so.

I don't think you really need to care too much, take one value for last year's period with the default temp (15.5?), and this year's period and can simply compare the ratio. 

There is a a lot of documentation around it on the page or this page talks about calculating it too, unfortunately using BTUs and Farenheigt 😅

https://www.greenbuildingadvisor.com/article/out-with-the-old-in-with-the-new

Martyn1981

Martyn1981 said:

Reed_Richards said:

I have tried degreedays.net and it  makes very little sense to me.  Instead of giving you the basic information, which is the average temperature for any particular day, it obscures that information by telling you days that were warmer than some specified temperature.  I'm sure in some specialised contexts this is useful but I do not find it so.

I had a quick look at the anomaly maps on the Met Office site, and it seems to show Dec20 being average to below average depending on location, and Dec21 being fairly average. Then Jan21 quite a lot below average, but of course Jan22 is not yet available, but seems like a warm one to me. So both suggest a tad warmer which might account for some of the improvement, given it does seem like quite a lot, as you say.

Fascinating stuff, many thanks for all the details and updates.

Quick update, the Jan 2022 image is now available, so if you choose mean temp and switch back and for between 2021 and 2022, you'll see last year was colder than average across the UK, and this year was average in the south to above average in the middle to north. Hope this helps.

Doh! Why didn't I just post them??????????????

QrizB

Martyn1981 said:

Quick update, the Jan 2022 image is now available ...

So down at my end of the country 2022 was slightly warmer than 2021, but up near Mallaig it was positively tropical!

Reed_Richards

I'm in the -1.5 to -2.5 range in 2021 and the 0.5 to 1.5 range in 2022 so that's a 3 C difference - which has got to be quite significant.   In 2021 I would have needed at least 15 % more energy to keep the house warm and the heat pump would have run less efficiently because of the lower outside temperatures.