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Heat Pump Running Costs

  • 28-01-2023 7:49am
    #1
    Registered Users, Registered Users 2 Posts: 823 ✭✭✭gandalfio


    Hi,

    How many units/kwh per day should a Samsung/Joule heat pump and hot water system use?

    How many units/kwh would be average daily or monthly total for all electricity including heat pump?

    Our smart meter is showing we've used over 500 units over the past 12 days since the beginning of the billing cycle. Cannot fathom how we're using so much. The heat pump used 120kwh last week. We've figured out why and have brought it down to about 9 or 10 kwh per day. So there's something else causing massive energy use. We're careful and take all the usual measures, switching appliances and lights off when not using them etc.

    Could the meter be faulty?

    It's in a new build A2 rated 3 bed semi. No gas.



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Comments

  • Registered Users, Registered Users 2 Posts: 823 ✭✭✭gandalfio


    Took a reading yesterday at 7pm and just now at 8am and there's a difference of 10 units.



  • Registered Users, Registered Users 2 Posts: 1,341 ✭✭✭Nelbert


    My heat pump pulled 132kWh last week. Mostly on night rate. A3 rated refurb.

    Do you know exactly what was on and off overnight? Do you know if the heat pump is 8 of those 10 for example?

    I think both pricing and the reporting of these modern systems has got everyone more aware of what they use which is good for monitoring but can cause you to go down perception based rabbit holes. I always remind myself "no gas bill" which in winter was significant.



  • Registered Users Posts: 118 ✭✭simpsimp


    We're in an A3 refub and the heat pump is using around 150kWh per week since start of the year, depending on external temperature.

    This will drop off precipitously once Spring takes hold.



  • Registered Users, Registered Users 2 Posts: 823 ✭✭✭gandalfio


    Ok so it seems the heat pump isn't necessarily the problem if our kwhs are less than yours. Would more than 10 kwh daily on the heat pump not be considered excessive?

    What's your total kwh/units used including the heat pump? Trying to figure out how many non heat pump units are on an average bill. There's over 400 or so non heat pump units used over the past 12 days.



  • Moderators, Home & Garden Moderators Posts: 6,425 Mod ✭✭✭✭graememk


    What info can you get from the heatpump?

    Is it splitting up the amount of heat going to your Domestic hot water and the Space heating by any chance?

    400 units over 12 days, is still 33 odd kwh per day.

    Its unlikely that the meter is faulty.

    Lights/appliances on standby, especially in a new house is insignificant, Most bulbs only use a few watts, and if you had all the lights on, i dare say it still wouldnt pass 100-200w!



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  • Registered Users, Registered Users 2 Posts: 823 ✭✭✭gandalfio


    I'm not sure if it's doing that or how to check. I would have thought heat pump plus electricity would be combined 10 to 15kwh per day max (600 to 900kwh or so for a 2 month bill). Otherwise its no cheaper than our old combined winter gas and electricity bills in a C rated house.



  • Registered Users, Registered Users 2 Posts: 823 ✭✭✭gandalfio


    For example, 15kwh per day is 900 over 2 months. 900 at 40c per unit is €360 before VAT and standing charges.



  • Moderators, Home & Garden Moderators Posts: 6,425 Mod ✭✭✭✭graememk


    Gas is now 13-14c now per kwh, bear that in mind too, not the 4-5c of other years. so triple that gas (and possibly electric) bill! (how many kwh did the old house use in the winter bill? does the new house feel warmer/more comfortable than the old one?)

    As your in a new house, you are likely getting a good COP, say 4, So for every 4kwh of electric you are using for heat, you are getting 4kwh of heat into the house.

    10 kwh/day wouldn't be that unheard of for electric alone. never mind Water and space heating. Oven, Tumble dryer, hob, it all adds up.

    Do you get more accurate breakdown of use with the smart meter?

    Another thing to look into is a home energy monitor, which will get you a far more responsive look into your house usage (you'll be able to spot some of the big consumers of power straight away)

    As all you have right now is meter reads, you could even shorten the period of readings to an hour or 2

    eg a base load of 500w over 2 hrs will be 1kwh



  • Registered Users, Registered Users 2 Posts: 823 ✭✭✭gandalfio


    Can't remember howany units in the old house, but winter gas and electricity was never more than 350 euro combined. The new house is far mor comfortable and warm than the old one.

    Smart meter only gives readings, no breakdowns.

    Yes will get a monitor and get to the bottom of things.



  • Moderators, Home & Garden Moderators Posts: 6,425 Mod ✭✭✭✭graememk


    That's my point re last years bills, Its Doubled, nearly tripled in prices. I've heard of people getting gas bills pushing €1000. Cant really compare this year with last, with the crazy rise in energy prices.

    But on the otherhand, you do have a more comfortable house now, and that still takes energy.



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  • Registered Users Posts: 1,789 ✭✭✭PowerToWait


    Like, electricity has increased by over 60% in the last 12 months alone. So a hundred quid leccy bill is now 160. Many people seem to be forgetting this.


    Everyone's electricity is stupidly expensive nowadays.



  • Registered Users, Registered Users 2 Posts: 823 ✭✭✭gandalfio


    To clarify, the final bill we received in the old house was from October to December. So the unit prices are very similar to now.

    My main point is about the amount of units being used. It's way way higher in the new house.



  • Registered Users, Registered Users 2 Posts: 823 ✭✭✭gandalfio


    Our combined gas and electricity from October to December was 332 euro. In a 30 year old C rated house.

    Our smart meter is showing 500 units used in the past 12 days alone. In a brand new A2 rated house.



  • Registered Users, Registered Users 2 Posts: 823 ✭✭✭gandalfio


    The point of the thread was to ask people how many kwh per day is typical usage for an air to water heat pump in a new build A2 rated house. And how many daily units is typical usage for everything else.



  • Registered Users Posts: 1,789 ✭✭✭PowerToWait


    Well it depends on the size of the house, efficiency of same, external temperature, type of heating (rads or UFH), desired temperature, number of showers etc.


    My own is modest at 175 sq metres, good leak test, super insulated, UFH. 2 adults away all day.


    I used under 15 kWh some milder days this month, up to 28 kWh when drops to zero and below. House is 20 - 21 degrees 24/7.



  • Registered Users, Registered Users 2 Posts: 438 ✭✭jasgrif11


    I have a Geothermal (vertical). It’s the Nibe 1240. Yesterdays usage was 25.68kWh and cost €7.59 (on Energia Ev tariff).

    Family of 5 and house 300sqM



  • Registered Users, Registered Users 2 Posts: 823 ✭✭✭gandalfio


    I should mention that our house is 115sqm semi D.



  • Registered Users Posts: 1,789 ✭✭✭PowerToWait




  • Registered Users Posts: 1,789 ✭✭✭PowerToWait


    It might be worth looking into air leaks, some of these would be easy and not expensive to fix.



  • Registered Users, Registered Users 2 Posts: 823 ✭✭✭gandalfio


    Any idea how many kwh per day the heat pump should be using? A2 rated, 115sqm.



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  • Registered Users Posts: 1,789 ✭✭✭PowerToWait


    Sorry, just saw this. I’ve no clue tbh, lots of variables. People on here say 15 - 20. Depends on many factors.



  • Posts: 0 [Deleted User]


    Heat pumps seem to be an absolute drain on finances for some people.

    Demand for them must be plumetting in the era of high electricity prices.



  • Registered Users, Registered Users 2 Posts: 455 ✭✭zoom_cool


    My heat pump used over the last week between 11 - 14 kwh per day for 205MSq house which is retrofitted. UFH downstairs and RAD's upstairs includes Hot water also.



  • Registered Users Posts: 114 ✭✭Scoopsire


    @zoom_cool what level of retrofit had you done? Windows, ground floors, external insulation etc?

    11-14kWh seems pretty ok



  • Registered Users, Registered Users 2 Posts: 4,755 ✭✭✭jackboy


    Oil heating is still vastly superior for the majority of Irish houses. Unless your house is built or renovated by top class builders forget about heat. pumps.



  • Registered Users, Registered Users 2 Posts: 455 ✭✭zoom_cool


    Triple glazed Windows, External wall Insulation 120mm, Internal wall insulation 50mm, Underfloor Insulation 150mm and I need to update attic only have 150mm Rockwool



  • Moderators, Home & Garden Moderators Posts: 6,425 Mod ✭✭✭✭graememk


    It's more like oil is vastly easier not superior. You can just get away with it and just oversize the oil boiler to make up for the losses

    Heat is heat at the end of the day be it electric/oil/gas/farts.

    Oil isn't cheap either. Currently on par with night rate electric alone, not counting the 3-4x boost the heatpump generates.



  • Registered Users, Registered Users 2 Posts: 1,341 ✭✭✭Nelbert


    Heat pump costs are a lot more visible. That doesn't mean they are higher. December and January was in the region of €150 for heating and hot water each month for me. My old gas bill was multiples of that for the winter months.

    Next door neighbour spent about €250-300 for November with gas boiler. And my house is occupied all day during the week while neighbours is empty and not heating.

    Ive lost some of the net savings I'd have made if not for the price growth but I'm still measurably better off.



  • Registered Users, Registered Users 2 Posts: 596 ✭✭✭theintern


    Over winter my heat pump is using between 60 and 100kwh per week. There was a higher week back in December of 140 in a week when it was really cold and below zero.

    A2, slightly larger house than yours. We keep the house warm (21 on the thermostats) all the time pretty much.

    I think it's fantastic to be honest. Similar bills to what we used to have in a smaller apartment using gas, and that's before taking into account the changes in energy prices.

    Wait till you experience the house from March onwards. According to my unit, it used basically zero electricity from March to November. So this is as high as your bills will get.



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  • Registered Users, Registered Users 2 Posts: 4,755 ✭✭✭jackboy


    To get the value you are seeing you must have a well constructed well insulated house.



  • Registered Users, Registered Users 2 Posts: 2,530 ✭✭✭ECO_Mental


    Here is my moving 7 day average of my heat pump to take up the ups and downs over the last 12 months practically. A1 new build house 210m2 House (A2 without Solar PV)

    As you can see during an average winter day its between 20-25 kWh/day, from about April to October I was doing about 5 kWh/day or less

    The big spike in December was obviously the very cold snap we had for a week or so. 2 adults and a 17 and 19 year old that like to take VERY long showers at least once a day so that contributes a lot to the consumption. Underfloor heating everywhere including upstairs and I think I have 13 zones!

    I am happy with it no stat set above 20 deg and all bedrooms and halls set to 19 degs. I log it using home assistant so I can see if its on all the time and usaully someone has set a stat to 22 degs or something.


    6.1kWp south facing, South of Cork City



  • Registered Users, Registered Users 2 Posts: 1,341 ✭✭✭Nelbert


    Well insulated yes. House is 1970s semi-D post renovation (full gutting, 90mm dry lining on main house, 120mm on extension, 150mm underneath ground floor, spray foam in the attic dormer) still some queries on air tightness but nothing major.

    Heat pump set to heat on night rate gives us a pleasant wake up then solar gain can take us through to night rate most of the time (sometimes overheat us!).

    Recent automation to boost hot water if below a certain temp at 7am means less likely to heat water on day rate too.

    So mixture of insulation and being smart as possible on when to call for heat to keep costs down.

    With the milder weather of the last week I'm already seeing drop off in energy usage (improved efficiency and less heat demand).



  • Registered Users, Registered Users 2 Posts: 1,508 ✭✭✭DC999



    Hats off @theintern + @zoom_cool. That's an amazingly low amount per day. To give a comparison, heating our 5x5m sitting room / kitchen (old 'leaky' house) is using the same as your whole house. That's heated between an electric rad and gas boiler rad and set to 20.5C.



  • Registered Users, Registered Users 2 Posts: 455 ✭✭zoom_cool


    @DC999 thanks for comment I think more is to do with the auxiliaries and not the heat pump like flilow rates on the manifolds and heat pump on weather compensation and lots of plumbers don't want to know how to setup correctly. You need to tweak them until you hit the sweet spot.



  • Registered Users, Registered Users 2 Posts: 823 ✭✭✭gandalfio


    Cheers for all the replies. We've managed to bring the daily usage right down through lots of tinkering. Last few days read 9.2, 8.8. 7, 6.6, and 4 yesterday.

    We've been leaving the downstairs stat at 18 once we go to bed and pretty much leave it there until the following evening.

    However, whilst our overall energy usage has come down greatly, it has plateaud and we're using the same amount of units per day whether the heat pump is running at 9kwh or 4. All other appliances, lights etc are being used in the same way each day.

    Any reason why this could be happening?

    Another issue were having is the following. Two of our bedrooms don't heat as well/retain heat as well the master bedroom.

    The master bedroom is always really warm and the rad is never turned above 3. Whereas the other rooms' rads are all turned to 5 and still have issues heating and retaining heat. 

    It seems that its more retaining the heat is the issue as the radiators have been tested and are working well.



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  • Registered Users, Registered Users 2 Posts: 1,341 ✭✭✭Nelbert


    If it's heat retention check for air tightness. Seals around windows and properly installed vents (with seals around it so that air travels through the intended part and not gaps around it).

    Other thing is location. Our rooms with south east facing windows call for less heat than our north west ones especially in winter.



  • Registered Users, Registered Users 2 Posts: 9,268 ✭✭✭893bet


    Are those rooms on the north side of the house?

    Is there potentially additional air leakage in them?

    Your problem sounds like a heat retention issue overall. Was there an Airtightness test done on your house during build?



  • Moderators, Home & Garden Moderators Posts: 6,425 Mod ✭✭✭✭graememk


    Most likely that it is warmer outside.

    Do you notice a rise when more showers or baths are taken in a day? Your heating your hot water too.

    A 200L tank if heated by an immersion could easily use 10kwh.



  • Registered Users, Registered Users 2 Posts: 823 ✭✭✭gandalfio


    One of the rooms is dual aspect, one window facing east and the other facing south. The other bedroom is facing west.

    No difference re shower usage etc. The overall meter reading is consistently the same every day the last week day. Even when one day on the heat pump was 9 and yesterday was 4.



  • Registered Users, Registered Users 2 Posts: 823 ✭✭✭gandalfio


    We're only living in the house 6 weeks. Builder has sent Joule heat pump technicians round. They recalibrated the thermostats (stats were reading the temperature 2 degrees above what our own thermometer showed). But the heat retention issues remain in the two bedrooms and the downstairs bathroom. Joule suggested the stats might need to be moved, or the rooms need bigger radiators. But the builder is refusing to budge and won't offer anymore assistance. Is there anything else we can do here?



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  • Moderators, Home & Garden Moderators Posts: 6,425 Mod ✭✭✭✭graememk


    No idea where to go re the builder. (although 4kwh a day for heat is pretty good!)

    but

    Wheres the thermostats for the bedrooms, All individual? or a shared stat?

    My thinking is : Changing the thermostatic valve, doesnt create a call for heat, just tries to put a upper limit of the heat.

    Master bedroom gets warm first, maybe its the first on the loop, the thermostat is also satisfied, heating turns off, other bedrooms get nothing. (even though they are at 5)

    What happens if you turn the master bedroom off completely?

    Are you taking meter readings for the Kwh value or is that just the heatpump?



  • Registered Users, Registered Users 2 Posts: 823 ✭✭✭gandalfio


    The 4kwh per day was just yesterday when it pretty much no heat was called for for the day.

    There are 2 stats. One in the hall, and one on the landing.

    Haven't tried turning any rads off completely. We were told by the plumber never to turn any to 0. Any idea why?

    The readings I've been taking are under the daily/weeks usage statistics on the panel attached to the tank in the hot press. I'm also taking daily unit readings from the main energy meter for the house.



  • Moderators, Home & Garden Moderators Posts: 6,425 Mod ✭✭✭✭graememk


    I understand, so the 4kwh is heat only then? Not the rest of the house.

    Don't know why not to turn off completely, possibly to do with efficiency but once temperature is reached for the rad valve it would be closed see this : (heat geek)

    https://youtu.be/zpTVIeUh04E

    But as one room is too warm I'd be considering closing the lockshield on the other side of the radiator a bit more, to restrict flow to that radiator and allow more heat to go to the other rooms.

    The other rooms might not be properly heated as the thermostat could be cutting out too soon. Thats why I suggested to turn the master bedroom off completely, just to see what changes.



  • Registered Users, Registered Users 2 Posts: 823 ✭✭✭gandalfio


    Yeah the 4kwh is for heat only. But the meter readings for entire house are the same each day even though the heat is fluctuating from 10kwh per day to 4kwh. Can't understand why.



  • Registered Users, Registered Users 2 Posts: 596 ✭✭✭theintern


    The only way to work this out is to get something like a Shelly EM (I have one of these) and hook it to your heat pump circuit and the main circuit. Or get an _Emporia Vue 2_ (I think that's the name) that seems to have a bunch of clamps so you could clamp every circuit.


    Then buy some power monitoring plugs to monitor specific appliances like the washing machine etc.

    You'd be surprised how much some appliances use like the cooker, washing machine etc. A night rate meter and sticking these on timer can make a big difference. Home Assistant provides a great dashboard to bring this all together.


    EDIT - I was thinking of the Emporia Vue 2.

    Post edited by theintern on


  • Registered Users, Registered Users 2 Posts: 596 ✭✭✭theintern


    I just went into the settings of my unit. My above estimations weren't including power used by the indoor unit, just what was used by the outdoor unit (different circuits on my fuse box), so were under estimating overall system usage. The nice thing is now I have readings for the total electricity input to my A2W system over the year. Here it is.

    140sqm new build, A2. Thermostats generally @ 21 degrees.

    Figures are total energy units used / total heat units generated (heat pumps being greater than 100% efficient

    Jan - 467 / 1396

    Feb - 318 / 956

    Mar - 262 / 726

    Apr - 136 / 367

    May - 69 / 153

    June - 65 / 146

    July - 68 / 134

    Aug - 62 / 139

    Sep - 87 / 215

    Oct - 204 / 645

    Nov - 339 / 1084

    Dec - 683 / 1657

    Total - 2760 / 7618 - 276% efficiency.

    7.56 units per day consumed

    Max units per day across a month - 22.03 (Dec)

    Min per day across a month - 2 (Aug)

    On my current price plan (EI, 5.5 discount, day/night meter, assuming usage of 66% day rate vs 33% night rate usage) works out at a hair under €1000 for the year. €998 to be precise. Assuming 2023 is like 2022. In reality the cost was less than this for 2022, as I was on a better plan.



  • Registered Users, Registered Users 2 Posts: 823 ✭✭✭gandalfio


    How do you find the total units for indoor and outdoor combined? Are the units shown on the digital panel on the hot water tank for indoor or outdoor?

    Separate question, is 60 degress for 20 minutes once a week sufficient for anti-legionella?



  • Registered Users, Registered Users 2 Posts: 596 ✭✭✭theintern


    It's a Daikin unit and shows the total units consumed. The units it displays as used for heating are the exact same as what my clamp is measuring on the 'outdoor' circuit in my circuit board, and then on top of that there's energy used to heat water. It shows each separately and also shows the total.



  • Registered Users, Registered Users 2 Posts: 1,341 ✭✭✭Nelbert


    This is good info, my usage is similar, but my monitoring only started properly in August and I've been eager to establish what my water heating requirement is to consider an Eddi for hot water in summer. I thought it would be a purchase based on convenience rather than return on investment financially. But if you consider your March to September usage it's ~3 years payback (rough day rate of 40c longer if you consider night rate but with my hot water usage profile day is more appropriate for me) which is reasonable given the additional convenience Vs cheaper alternatives that wouldn't be as smart in terms of limiting to excess.



  • Registered Users, Registered Users 2 Posts: 1,508 ✭✭✭DC999


    If you have a D/N meter heat the water at night and stop just before cheap rate ends. Then you only need to boost during day.

    If it's a well insulated tank, and ideally large enough too, set the immersion to a hotter temp. Means you've stored hotter water and dropping a bit in temp during the day matters less. Then it won't need much boost immersion heat for showers later in the day.

    You can try that before getting an Eddi and see how it goes.



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