I bought a Heat Pump

matelodave

waiting with keen anticipation especially if you've got data on oil consumption v leccy to compare consumption with costs

michaels

Reed_Richards said:

I will have had the heat pump in place for exactly a year on 12th December.  My plan is to give a detailed update then when I have a full year's worth of data.

Worth digging out the historical temperature records from your nearest weather station as we can see just from our gas consumption that for example a mild January can use a lot less gas than a cold November and 12 months is certainly not long enough for things to balance out between years.

Meatballs

michaels said:

Reed_Richards said:

I will have had the heat pump in place for exactly a year on 12th December.  My plan is to give a detailed update then when I have a full year's worth of data.

Worth digging out the historical temperature records from your nearest weather station as we can see just from our gas consumption that for example a mild January can use a lot less gas than a cold November and 12 months is certainly not long enough for things to balance out between years.

Degreedays.net can grab this for you and has resources on calculating all the data properly 😅

michaels

Meatballs said:

michaels said:

Reed_Richards said:

I will have had the heat pump in place for exactly a year on 12th December.  My plan is to give a detailed update then when I have a full year's worth of data.

Worth digging out the historical temperature records from your nearest weather station as we can see just from our gas consumption that for example a mild January can use a lot less gas than a cold November and 12 months is certainly not long enough for things to balance out between years.

Degreedays.net can grab this for you and has resources on calculating all the data properly 😅

Thank you, really useful

Verdigris

shinytop said:

@Reed_Richards

I thought I'd bump this thread to ask how things are going now electricity has gone up so much and temperatures are going down.  I'm just settling into my first ASHP winter and trying to find the best way to run things.  

This article on running heat pumps efficiently may be of interest:

https://energysavingtrust.org.uk/how-to-ensure-a-heat-pump-runs-efficiently/

Probably has mostly been covered, here, but may be handy to have a quick reference.

shinytop

Verdigris said:

shinytop said:

@Reed_Richards

I thought I'd bump this thread to ask how things are going now electricity has gone up so much and temperatures are going down.  I'm just settling into my first ASHP winter and trying to find the best way to run things.  

This article on running heat pumps efficiently may be of interest:

https://energysavingtrust.org.uk/how-to-ensure-a-heat-pump-runs-efficiently/

Probably has mostly been covered, here, but may be handy to have a quick reference.

That's not a bad reference; it covers the basics. I've been messing around with these points on mine and I'll post some of my findings when @Reed_Richards reveals all from his.

Reed_Richards

In order to qualify for the Renewable Heat Incentive you must have an electricity meter fitted that monitors the power consumed by your heat pump.  I took my first reading (172.04) on 13th December 2020 and read it again at the same time past the same hour today (7102.90).  So the amount of electricity consumed in exactly a year was 6930.86 kWh.  I had some teething troubles with my heat pump in the first week, a blocked filter that was a "known bug".  Thereafter I haven't had any problems  

Before that I had an oil boiler, installed in 2012, a condensing combi.  The oil tank was "filled" on 4th February 2019, twice more and then again on 6th February 2020.  The total oil used was 1936 litres.  If you assume 10.35 kWh per litre of oil that is 19928.4 kWh per year.  But that would be if the boiler was 100% efficient.  I am going to guess that it was 90% efficient in which case I would have used 17936 kWh during the year in question.

Is it a fair before and after comparison?  I heated most of my house to much the same temperatures before and after.  But I took the opportunity to put the two bathrooms on a second zone so I could heat the towel rails when I wasn't heating the rest of the house; that will have increased my energy consumption.

The hot water is completely different before and after.  Before I had a combi with such long pipe runs that if you wanted to wash your hands you would lose patience waiting for hot water.  And if you waited long enough then a large quantity of water was left in the pipe, typically over a bucket full.  Now I have a hot water cylinder and a re-circulation pump that runs for 5 minutes every hour from 7 am to 11 pm.  This pumps hot water round a loop of well-insulated pipes and back into the cylinder.  As a result all the hot taps now give hot or warm water very promptly. But this will be costing me energy.  For around 6 months of the year I can also use spare solar electricity to heat the tank via the immersion heater on sunny days.  This is saving me electricity.  I don't know how the increased costs and increased savings balance out.

Then there is the weather.  Memory tells me we had a milder 12 months from February 2019 than we have just had for the last 12 months.  I know there is data you can look up but I have not yet got my head around "degree days".

So superficially I used maybe 17936 kWh of oil before and 6931 kWh of electricity with the heat pump.  A straight ratio gives me 2.59.  The data I was given indicated I should achieve and average Coefficient of Performance for heating and hot water of around 3.  So 2.59 falls short of 3 but it's not really a fair comparison for the reasons I have stated.

The oil I bought for the 367 days I am comparing cost me £870.  The electricity would have cost me £900.50 had Symbio, my electricity supply company, not gone under and electricity prices skyrocketed.  At the moment the average price of heating oil is about 59p  per litre.  The average I paid was 44.94p per litre which means that the price I pay for electricity has gone up more than the price I would be paying for heating oil.

So all that I can really conclude is that a heat pump can indeed use a lot less energy that other means of heating, the performance can be fine and the running cost is broadly comparable to that of an oil boiler.  But I have given dates and figures that would allow anyone who wishes to delve deeper and I am happy to answer questions.         

                      

QrizB

Thanks R_R!

I've just downloaded the degree-days for the last 24 months for EGUB (RAF Benson, notionally the closest to me that's listed at https://www.degreedays.net/ ).

• 13/12/19 to 12/12/20 - total 1927 degree-days
• 13/12/20 to 12/12/21 - total 2165 degree-days
  

That suggests that the last 12 months have needed ~12% more heating input than the previous 12 months, as a first estimate at least. Which *might* mean your COP is more like 2.9.

Reed_Richards

I just cannot figure out degree days @QrizB .  Don't you need to specify a base temperature?  What base temperature did you use?  I actually need to compare 13/12/20 to 12/12/21 with 4/2/19 to 5/2/20 (x365/367).  

QrizB

I stuck with the default base temp of 15.5C (60F), as I couldn't come up with a good reason to use anything else! I'll see what data I can find for your earlier period and then do the same man-maths.