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Electricity use for heat pumps - comparing homes and consumption

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Morgan
(@morgan)
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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.

@editor 

You shall have to let us know the results.

 

Retrofitted 11.2kw Mitsubishi Ecodan to new radiators commissioned November 2021.


   
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 SKD
(@skd)
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@glpinxit Thanks for all this info.  It's much appreciated.

With hindsight I wish I had specified a dedicated HP consumption meter.  Using my pre-ASHP elec meter records I've estimated a relative overall FTC consumption over-read since ASHP commissioning (two years) that's very similar to yours.

Your COP improvements really are impressive.  I guess you reduced your pump flow rate to increase your delta t?

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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Marzipan71
(@marzipan71)
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Hi @skd just thought I'd add that a conversation with @toodles drifted in this direction also - some data for two Daikin-powered homes here. Not in thread but pertinent is that the first year (calendar year 2021) I had my ASHP I was clueless how to operate it and our annual grid consumption was nearly double what it was for calendar year 2023 - 18k kWh v 10k kWh. Now I'm just fine tuning. All improvements thanks to folks on this forum.


   
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(@glpinxit)
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@skd Thank you. I've set myself the objective (for now at least) of not making fundamental changes to the design or our ASHP system. Instead I'm seeing if I can get things so I'm happy overall. This means that I'm tolerating the third-party room thermostats (by relying on weather compensation thereby taking them out of the equation). I'm also living with the presence of the low-loss header and its two attendant pumps.

The low delta-T was always a bit of a concern. Last Spring I turned it down in the controller settings from 5 to 4. This didn't appear to make any difference. In early January '24 I returned to the problem and turned the pump setting from 4 to 3 which still made no difference. So I read the manual for the pumps.

From my reading, with a LLH it seems important that the primary pump runs slightly slower than the secondary pump- the opposite of how mine was set up. The pumps are Wilo Younos Pico. The primary pump was set at 'max-underfloor' (think this is max flow and head) and the secondary was also on a slightly less high

IMG 3768

setting. I've turned the primary right down to just below 'mid-radiators' which the manual says is right for 17 rads and the secondary to just above this. Handily the pumps each have a digital flow-rate and power consumption display which helps.

I think you will see when I made the change in the attached photo...


   
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 SKD
(@skd)
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@glpinxit Thanks for this - really useful.  We have the Ecodan cylinder with LLH with two emitter zones.  I'm currently monitoring flow temperatures across the LLH with a few to minimising temperature differentials via pump speeds, in conjunction with maintaining an efficient delta t.  Your info is a great help with deciding on the pump settings.

Thanks again.

(Apologies for drifting off topic with this one.)

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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MikeFl
(@mikefl)
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My figures thus far (just for heating and DHW). Installation in April 2023, but only gathered figures from June.

Month kWh Average Outdoor Temp
Jan 2024 1034 4
Dec 2023 891 5.5
Nov 2023 724 6.2
Oct 2023 355 10.7
Sept 2023 97 15.3
Aug 2023 52 15.8
July 2023 52 15.5
June 2023 23 19.1

House is a converted bungalow, downstairs being around 100sqm; upstairs 40sqm. Radiators only. Downstairs also has a flat roof extension. Cavity walls insulated in 2005. Cumbrian village.

Making changes throughout winter to improve efficiency, and hoping for better by next winter.

Grant Aerona 3 10kW


   
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(@sunandair)
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Posted by: @glpinxit

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.

Hi @glpinxit your reply to @skd is very enlightening. Am I right in interpreting your numbers in brackets? 

For example  “Nov 399 KWh (442)”

Is the 442 the data estimated and produced from the main controller on the Ecodan? While the 399 is your actual energy consumed as derived from your HP energy meter?

I’m thinking the ecodan estimates are likely to deviate in variability from one month to another because they are after all, estimates. So consistency isn’t something I would be looking for but rather, a general trend of inaccuracy. In all monthly sets the main trend appears to be an over estimation of around 10.7 to 8.4 percent. This to me is a good starting point in accounting for ecodan over estimated consumption. 
But obviously this is only relevant if you don’t have an actual consumption meter. 
I don’t have a consumption meter, whereas you do. So perhaps it means more to me than it does to you. So thanks for posting it….


   
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(@glpinxit)
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@sunandair rather than keep cluttering up this thread I'm going to start a new thread about my Ecodan's figures for its energy consumption. I'll include the % month by month and yearly for 2023. (But first I'm going to do today's chores.)

To answer your specific question, yes 442kWh is the Ecodan's estimate and 399 is what the third-party consumption meter measured for that month. 


   
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 JEH
(@jeh)
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We have a 5-bed detached, whole house heating on 24x7 at 20-22°C. According to the heat pumps themselves we used Feb/269kWh Jan/391kWh Dec/324kWh Nov/293kWh for heating. It's a very open-plan 40 year old Swedish house in Sussex, heated entirely by two 3.5kW A2A mini splits.

We used the immersion for DHW and the bills (including standing charges) are £114 £157 £154 £131 respectively.  We still have a gas meter but it's turned off, so the bill includes a standing charge for that. With Octopus Cosy and batteries we pay about 20p/kWh. We also have MVHR and generated 517kWh of solar in those four months.


   
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Mars
 Mars
(@editor)
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@jeh welcome to the forums and thanks for sharing your numbers. Very healthy performance - there’s a lot to be said for A2A systems. Very underutilised in the UK.

This post was modified 2 months ago by Mars

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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Mars
 Mars
(@editor)
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Here’s our data for winter 2024, from mid December to mid March.

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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Toodles
(@toodles)
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@editor Can’t access last year’s readings very readily as they were re-set when the Homely controller was fitted but… January 2024 = 829 kW/h and February = 504 kW/h. Up until March 16th. = 293 kW/h. Regards, Toodles.

Toodles, 76 years young and hoping to see 100 and make some ROI on my renewable energy investment!


   
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