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Electricity use for heat pumps - comparing homes and consumption

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Mars
 Mars
(@editor)
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@heacol will be fixing our heat pump system in the spring – loads of potential issues so really keen to see what he does. We'll be fully documenting the changes. Our lifetime COP is 2.71, so hopefully that'll get improved.

Currently we're doing between 1,000-1,200 kWh per month for the 18kW unit, running on WC.

Buy Bodge Buster – Homeowner Air Source Heat Pump Installation Guide: https://amzn.to/3NVndlU

Follow our sustainability journey at My Home Farm: https://myhomefarm.co.uk


   
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 MPHB
(@mphb)
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image

This are my data for my first full year of running a 10kW Midea which heats 250m2 of UFH in a 1980's house with original double glazing. LWT sits between 35 (10aT) and 48 (-6aT) with an indoor temperature of 19.5-20.5.

The heat produced is a number from my Wilo seconday pump which gives me rolling kWh numbers and a number for cumulative heat (or "cold" for defrosting) produced. This number is overstated though, as the RWT of my UFH circuit was measured by a PT1000 sensor taped to the return pipe and so undestating the return temperature, resulting in an overstated heat number. I only added thermal paste to the sensor two weaks ago, raising the RWT with some 1.5 degrees. Still, I am confident that (S)COP is solid over 4.

I am happy with the current consumption, which will go down as soon as we replace all old double glazing. Current consumption gives our 1980's house a A rating in Germany.

This post was modified 3 months ago by MPHB

   
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(@sunandair)
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Posted by: @sunandair

Ours is a 4 bed old house,180sq mtrs, no u/f heating just 16 radiators. Old farm workers cottage. Insulated internally.

My heating in Nov was 405kwh, Dec 451kwh and Jan 720kwh. We are located in The Cotswolds, I have an 8.5kW heat pump. We have low mass internally and no under floor slab to heat up.

Regarding flow temperature with radiators we can just about get down to 32C and more likely to be 35 to 40C depending on outside temp.

To help qualify our OKish performance... There have been improvements we have done in an attempt to help maximise our efficiency. These include:

  • We changed our 3rd party thermostat to the Mitsubishi wireless thermostat which has feedback coms with HP. allowing Auto Adapt to work properly.
  • we first adjusted the flow through our Low Loss Header
  • We then removed our Low Loss Header creating an open heating circuit with only one circulating pump ( this 9 m. head pump only operates at 49watts (so quite quiet.) and circulates all 16 rads incl 10mm copper feed to about half of the rads.
  • We screened our pipework and noticed some 22mm pipework where there should have been 28mm pipework. Ensured 28mm tee branches were used and only reduced to 22mm after the branch.
  • We checked that we only had one radiator connected to one run of 10mm pipework.

After these changes we have then been working on a setback nighttime operation which gives us 14.5 hours comfort temp at 20/21c between 8am to 10.30pm followed by 9.5 hours generally off period. This is actually a 7 hour setback temp of 17c for a period from 9pm to 4am. The saving this has given for our particular house has been variable depending on outside temperatures but roughly saves around 3 kWh per day at 10c. Compared to continuous operation. The reheating of the house after a setback is best achieved using Auto Adaptive which is quicker at recovery than weather compensation.

However this efficiency might not be achieved or necessary for an under floor heating setup since the lower temperatures and slow cool down of a heated slab comes with its own efficiency. We are just trying to make the most of some of the limitations of a radiators only installation.

B5452A79 529C 4E28 A5A9 5DC68C4AFB4F

This 24 hour chart shows the ideal recovery using 1c incremental temperature rises on a Auto schedule on the main controller.


   
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(@hughf)
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I’ll pull the numbers from the smart meter and let you know…

we’re on the backstop energy rate, and on prepayment… I top up around £70/week at the moment.

Off grid on the isle of purbeck
2.4kW solar, 15kWh Seplos Mason, Outback power systems 3kW inverter/charger, solid fuel heating with air/air for shoulder months, 10 acres of heathland/woods.

My wife’s house: 1946 3 bed end of terrace in Somerset, ASHP with rads + UFH, triple glazed, retrofit IWI in troublesome rooms, small rear extension.


   
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(@heacol)
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Posted by: @editor

@heacol will be fixing our heat pump system in the spring – loads of potential issues so really keen to see what he does. We'll be fully documenting the changes. Our lifetime COP is 2.71, so hopefully that'll get improved.

Currently we're doing between 1,000-1,200 kWh per month for the 18kW unit, running on WC.

  🤣 🤣 Lets see if we can double that SCOP, I do not think we will be that far off from what I understand of the system 😊 

 

Professional heat pump installer: Technical Director Ultimate Renewables Director at Heacol Ltd


   
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Mars
 Mars
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@heacol double? We are going to be aiming for a new British record 🤣

Buy Bodge Buster – Homeowner Air Source Heat Pump Installation Guide: https://amzn.to/3NVndlU

Follow our sustainability journey at My Home Farm: https://myhomefarm.co.uk


   
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(@heacol)
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Posted by: @editor

@heacol double? We are going to be aiming for a new British record 🤣

  SCOP 5.3, not even close to the UK record. 😀 

 

This post was modified 3 months ago by Brendon Uys

Professional heat pump installer: Technical Director Ultimate Renewables Director at Heacol Ltd


   
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Mars
 Mars
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@heacol that's my point, we'll need a double double. Get that COP into double digits and get people talking 🤣

Buy Bodge Buster – Homeowner Air Source Heat Pump Installation Guide: https://amzn.to/3NVndlU

Follow our sustainability journey at My Home Farm: https://myhomefarm.co.uk


   
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(@glpinxit)
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To stray back in the direction of the question asked by @Rad1o 

190sqm 4 bed house, conventionally built in 2004, two occupants.

11.2kW Ecodan retrofit 18 months ago. 270l DHW cylinder and 17 radiators (10 downstairs and 7 up on separate circuits).

Up to November 2023 on installer settings (plain vanilla WC curve- 50C at -3C OAT and 25C at +20C, thermo rad valves, two Salus thermostat/timers running day and night setback upstairs and night, only, downstairs).

From Nov '23 exclusively weather compensation with the Salus now set at 17C overnight upstairs and down and 17C upstairs in unoccupied daytime, otherwise at 23C. Thermo rad valves all set to max and WC curve gradually tweaked to current 45C at -5C and 26C at 20C. Various changes to pump speeds to give DT between 4C and 5C (from 2C to 3C previously).This keeps the house comfortably warm everywhere (around 20C) and generally more comfortable all round.

Electricity consumption as measured by a dedicated HP meter:

-October 2023 188 kWh, av temp 13.3C (2022- not recorded)

-Nov 399 kWh, 8.1C (2022- not recorded)

-Dec 436 kWh, 7,9C (2022- 809 kWh, 5.2C)

-Jan 2024 633 kWh, 4.8C ('23- 726 kWh, 6.5C)

-Feb '24 (so far) 205 kWh, 9.5C ('23- 484 kWh, 7.4C, full month)


   
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Majordennisbloodnok
(@majordennisbloodnok)
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Posted by: @cathoderay

There are a number of threads on this forum, some very detailed, that cover energy and/or electricity use (both matter, and of course they are related, by price per kWh). A number of us collect and post very detailed numbers for energy use.

...

I suspect I am one of the "offenders" here. I've posted energy production and consumption figures in a number of different guises on several threads here.

image

As you can see, there's quite a lot of seasonality involved. Our non-ASHP consumption has been a fairly consistent 9.5 kWh per day (averaged out over the whole couple of years), giving a good idea of how the cold snaps have hit the heating bill. I should also add that, averaged over the whole time, our DHW heating is about 3.25 kWh per day, varying of course, according to whether people are having showers or baths on a particular day or not.

For reference, we are a four-person household and the house is a three bedroom property heated by an 8.5kWh Mitsubishi Ecodan. My signature gives further details. We try to maintain the house at about 15degC overnight, raising to 17degC during the day and then a second jump to 19degC for the evening when we're sitting around being less active. I have no doubt we could find a more efficient heating regime but we don't want to be too warm at night or too cold in the evening so it works fine for us. If the weather does get too cold and the ASHP is a bit slow to respond, we cosy the house up with a log fire. The number of times we need to do that is small, whereas the number of times we want to do that is more.

 

 

105 m2 bungalow in South East England
Mitsubishi Ecodan 8.5 kW air source heat pump
18 x 360W solar panels
1 x 6 kW GroWatt battery and inverter
Raised beds for home-grown veg and chickens for eggs

"Semper in excretia; suus solum profundum variat"


   
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 SKD
(@skd)
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Posted by: @glpinxit

To stray back in the direction of the question asked by @Rad1o 

190sqm 4 bed house, conventionally built in 2004, two occupants.

11.2kW Ecodan retrofit 18 months ago. 270l DHW cylinder and 17 radiators (10 downstairs and 7 up on separate circuits).

Up to November 2023 on installer settings (plain vanilla WC curve- 50C at -3C OAT and 25C at +20C, thermo rad valves, two Salus thermostat/timers running day and night setback upstairs and night, only, downstairs).

From Nov '23 exclusively weather compensation with the Salus now set at 17C overnight upstairs and down and 17C upstairs in unoccupied daytime, otherwise at 23C. Thermo rad valves all set to max and WC curve gradually tweaked to current 45C at -5C and 26C at 20C. Various changes to pump speeds to give DT between 4C and 5C (from 2C to 3C previously).This keeps the house comfortably warm everywhere (around 20C) and generally more comfortable all round.

Electricity consumption as measured by a dedicated HP meter:

-October 2023 188 kWh, av temp 13.3C (2022- not recorded)

-Nov 399 kWh, 8.1C (2022- not recorded)

-Dec 436 kWh, 7,9C (2022- 809 kWh, 5.2C)

-Jan 2024 633 kWh, 4.8C ('23- 726 kWh, 6.5C)

-Feb '24 (so far) 205 kWh, 9.5C ('23- 484 kWh, 7.4C, full month)

many thanks for sharing this.  That's an excellent improvement that you've achieved with your adjustments.  Is your Ecodan controller an FTC6?  How have you found it's consumption reporting compared to your proper HP meter?  Any info greatly appreciated. Thanks again.

 

Mitsubishi Ecodan 11.2kW R32 ASHP; Ecodan DHW cylinder; UFH+rads
20x430W Jinko TOPCON Tiger Neo solar; Luxpower 6kW hybrid inverter; 10kWh LFP battery storage


   
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(@glpinxit)
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@skd the controller is an FTC6 but because of the third party thermostat/timers we don't have access to AutoAdaptation or to run the two heating zones on different profiles (I think that requires the Mitsubishi pre-plumbed cylinder and they were in short supply at the time). 

The controller generally over-estimates the power consumption. My previous table with Ecodan power replacing 

-October 2023 157 kWh (Ecodan 188- woops, mixed that one up last time!) (2022- not recorded)

-Nov 399 kWh (442) (2022- not recorded)

-Dec 436 kWh (478). 2022- 809 kWh (851)

-Jan 2024 633 kWh (686). 2023- 726 kWh (769)

-Feb '24 (so far, updated) 215 kWh (241). 2023- 484 kWh (521), full month

2023 full year 3144 kWh (Ecodan 3590). 2022- from installation to end of year 1713 (1897).

Annoyingly the disparity in figures is not consistent which undermines my confidence in its estimates of the power delivered so I have done my best to train myself to ignore the calculated CoP and focus on power consumed. (I'd like to believe that its error is consistent in its estimates for power consumed and delivered so the ratio might be roughly OK. Looking back over December and January, based on the heat pump figures the daily CoP is between 2.7 and 3.7 and if the meter figures are substituted it is a few tenths more.)


   
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