Meter Readings Panic and Electricity Costs

[canalsiderenovation]

I'm a bit concerned on our electricity use. We moved back into our house over Christmas and the ASHP was commissioned early December.

 

We have had the heating on 22 degrees with the room thermostats set at this temperature.

 

I took a meter reading on 7th Jan and it was 09359.1 and today it's 09945.3. This seems an awful lot in just over a week *slightly panicking and thinking we need to reduce our temperature*

 

Alongside this our fix is up for renewal and I've been looking at tarrifs.

 

We both work from home and we have (or will have soon once the electrician recovers from Covid) the solar working and the Solic 200 to divert excess to the Immersion.

 

Whilst I don't think Economy 7 will suit our lives I've been comparing tarrifs. Bear in mind we have never lived in an all electric house it's a bit difficult 

 

Symbio has a 12 month fix at 14.678pkw and 19.500 per day standing charge but Octopus seems to be as competitive with the Octopus Go charging 14.63pkw day and 5.00 during the hours of 00:30-04:30. Even if we don't use it during these hours the day rate is still competitive and we could set timers to charge things up. The standing charge is more expensive at 25.00 a day against Symbio but this Octopus still seems decent.

 

Finally, do we have a smart meter? I think it was installed by the last owner because we haven't done anything.

 

 

[SteamyTea]

So your house is pulling about 3.5 kW.

What are your heating load figures for the type of external temperatures you had last week?

 

May be worth doing some detection work.  Then you may be able to see if you have a large load on permanently.  Just a case of turning things off and looking at the remote meter display if you have one.

[Thedreamer]

That's seems like a lot of electricity.

 

We usually have a temperature of 19-20 degrees. Best thing to do is to reduce temperature and then monitor the change.

 

We are in a 3 bedroom all electricity house (but just have heat pump for hot water) and our usage is 10-11 units in the summer and around 13 units in the winter.

[SteamyTea]

2 minutes ago, Thedreamer said:

but just have heat pump for hot water

How do you heat the rest?

[canalsiderenovation]

1 minute ago, SteamyTea said:

So your house is pulling about 3.5 kW.

What are your heating load figures for the type of external temperatures you had last week?

 

 

Erm, how do I find this info out? 

 

I'm panicking! Probably before as we were only using about 250 units a month albeit we only had a stove for heating and our hot water was immersion/electric shower.

 

1 minute ago, Thedreamer said:

We usually have a temperature of 19-20 degrees. Best thing to do is to reduce temperature and then monitor the change.

 

I'm reducing all temperatures now to 19 degrees on the thermostat. The hot water we don't mess with and that comes from our heat pump.

 

£100+ a week in electricity seems crazy. 

[ProDave]

So in a week, you have used 586.2kWh

 

Assuming 16p per unit that's £93.79

 

That does seem high. What electricity were you using before the renovation (when presumably you had different heating?

[Thedreamer]

Just now, SteamyTea said:

How do you heat the rest?

Not going to say the bad word! ?

 

I bring the temperature up to 22 degrees in evening. When I retire to bed I bring the temperature to 24 degrees and then it gradually comes down over the night. It's usually 20 degrees in the morning and then depending on the solar gains and external temperature it might stay at that, but the coldest it been this winter has resulted in the temperature dropping to 18 degrees before I start the process again. From about March to Octoberish I won't need any heating.

[SteamyTea]

12 minutes ago, canalsiderenovation said:

Erm, how do I find this info out? 

By working out the heat loss for your construction type.

If you had a SAP done, it should be o there.

Or just work out the numbers from the areas i.e. floor, walls, windows, doors, roof, hove much insulation they have, that will give you the U-Value (eventually), then find a local weather station to get the last weeks figures, then work out the temperature differences, multiply that by your overall U-Value, multiply by hours in the week, and hey presto, you have your theoretical losses.

 

So say you have a 10m² wall that has a U-Value of 0.2 W.m^-2.K^-1, and the first two hours of the week had a mean temperature of -1°C, and your internal temperature was 18°C.

Then:

0.2 [W.m^-2.K^-1] x (18 - -1) x 10 [m²] x [ΔT] x 2 [time in hours] = 76 Wh.

 

Tedious, but useful, it is why we have spreadsheets.

 

Edited January 15, 2021 by SteamyTea

[canalsiderenovation]

11 minutes ago, ProDave said:

So in a week, you have used 586.2kWh

 

Assuming 16p per unit that's £93.79

 

That does seem high. What electricity were you using before the renovation (when presumably you had different heating?

 

We were using a max of 300 units a month and both working from home. We didn't have any heating as such as it was knackered oil so just used the woodburner or layered up but we had an electric shower and the water was all heated by immersion and we had all inefficient appliances and an oven which took an hour minimum to cook anything no matter what and we were paying the same rates as now.

 

I've turned all the room thermostats right down to 20.5 degrees now but now thinking I'll go down more. At this cost I'd turn the heating off completely and just burn wood! We still turn TVs off from standby but we have got now appliances on standby and the coffee machine and Quooker gets a lot of use.

Edited January 15, 2021 by canalsiderenovation

[SteamyTea]

If you have a 3 kW immersion heater on permanently, they you will use.

 

3 [kW] * 24 [hours in day] * 7 [days in week] = 504 kWh

 

Not far of what you have used.

 

Some heat pumps have a built in resistance heater, as does the storage cylinder.

[Thedreamer]

2 minutes ago, canalsiderenovation said:

 

just burn wood!

 

Come to the dark side on here. ?

 

If the circumstances are right, then it's worth considering.

[ProDave]

16 minutes ago, Thedreamer said:

Not going to say the bad word! ?

 

I bring the temperature up to 22 degrees in evening. When I retire to bed I bring the temperature to 24 degrees and then it gradually comes down over the night. It's usually 20 degrees in the morning and then depending on the solar gains and external temperature it might stay at that, but the coldest it been this winter has resulted in the temperature dropping to 18 degrees before I start the process again. From about March to Octoberish I won't need any heating.

I was trying to get an idea how much you were using on electricity when it was not powering your heating (not passing judgement on what that heating was)  to get an idea how much it has gone up now that it is powering the heating.

 

Edit you just answered that.

 

so 300 units pre renovation, 586 units now so assume other use has remained the same, that's 268 units or about £45 for a week of heating.

 

What did the old heating system (whatever it was) burn in a cold week?

[Thedreamer]

1 minute ago, ProDave said:

I was trying to get an idea how much you were using on electricity when it was not powering your heating (not passing judgement on what that heating was)  to get an idea how much it has gone up now that it is powering the heating.

 

I know you are in the stove club. Was for an early post ?

[canalsiderenovation]

7 minutes ago, ProDave said:

so 300 units pre renovation, 586 units now so assume other use has remained the same, that's 268 units or about £45 for a week of heating.

 

We were using 300 units a month not a week pre renovation!

 

11 minutes ago, SteamyTea said:

If you have a 3 kW immersion heater on permanently, they you will use.

 

3 [kW] * 24 [hours in day] * 7 [days in week] = 504 kWh

 

We only had our immersion on as and when pre renovation not consistently.

[newhome]

Did your installers not do a heat demand summary? This is the first page of the summary I received from an MCS installer when I asked for a quote. It was produced using the MCS software.
 

If it appears to be using much more electricity than you were led to believe I would contact the installers. 

 

Heat pumps are designed to be used pretty much constantly I believe but if you move to a variable tariff you could raise the temperature to higher than you need during the cheap hours so it does more work during the cheap rate and then set it back during the more expensive period. 
 

I’m on a flat rate tariff of 11.5p for heating and 12.59p for all other use with EDF. I don’t have a heat pump yet (still considering one) but am on all electric heating. I’ve never set the heating to 22 degrees though. I have it at 18 in the bedroom and between 18 and 20 in the living space. 

[canalsiderenovation]

16 minutes ago, newhome said:

I’m on a flat rate tariff of 11.5p for heating and 12.59p for all other use with EDF. I don’t have a heat pump yet (still considering one) but am on all electric heating. I’ve never set the heating to 22 degrees though. I have it at 18 in the bedroom and between 18 and 20 in the living space. 

 

I'll check our variable tarrifs. I've found some information from the MCS installers. 

 

 

 

 

[joe90]

As an aside, our build used a lot of electricity for the first few months and I put this down to “warming” the build up and drying out. Ours is set to 20/21’ now.

[AliG]

I do agree that this seems quite high and I would go through a process of trying to find what is using the electricity. The easiest thing to do first would be turn off the heating and to water see how much electricity you are using without these. Then experiment adding in just hot water and then the heating.

 

There have been a few threads on here recently re heating costs.

 

I have tried to estimate how much of the year's heat demand someone will use in a cold spell. The heat demand given for a house covers give or take 7 months of the year. The rest of the year the heating won't be on (Depends on your insulation and ability to withstand cold)

 

I then reckon that the coldest point of the year, usually January, will use just over 20% of the year's heating demand(from studying my own usage and calculation on my own house)

 

So if your heating demand is correctly calculated at 15000kWh a year. Then you would expect to use just over 3000kWh in January, give or take 100kWh a day when the outside temperature is cold. You could run the numbers but I think this is a good guesstimate.

 

Now what then alters things is using an ASHP, as the COP falls when it is cold, so your heat use will be even more skewed to colder days. Although the average COP is stated at 3.3 in the calculations, looking at the info on various heat pumps it could be close to 2 on a day when the outside temperature is 0 and you are heating water to 50. Thus you might expect to use around 50 kWh of electricity for heating on a cold day plus 5 for DHW. So 55 kWh a day for heating and hot water when the outside temperature is zero as it has been recently.

 

You seem to have used around 72 a day for the last 8 days, so this does not seem quite as crazy as it first appears.

 

Even an increase in temperature to 6 or 7C would see the COP rise and heating usage fall and electricity usage fall considerably.

Edit - Come to think of it. The reason you would get a very low COP is the flow temp. 50c is way too high. If I knew your pipe spacing etc I could get an idea of what it should be but assuming you have UFH everywhere you would only need about 25W a square metre at the most and you will be running way above this. The high flow temp will kill your COP and raise your heating costs considerably.

Edited January 15, 2021 by AliG

[TonyT]

Agree with Steamytea,

 

check immersion heater and everything to do with Hot water, that programmer if any isn’t on constant/ always on.

should be regulated by the thermostat in the immersion heater cover but worth a check anyway.

 

plus the electric shower will swallow a few units of electricity.

 

Process of elimination, Sherlock Holmes style!

[Temp]

Dropping the temperatures from 22 to say 19C will reduce consumption but not by a huge amount. If its 0C outside the temperature drop through walls and windows changes from 22 to 19 so I would expect consumption should go from 586 units/week to 586 * 19/22 = 506 units/week at best (as the DHW demand hasn't changed).

 

 

 

 

[ProDave]

"Total Design Heat Loss 8594W"

 

Assuming that is how much they have calculated the heat loss of the whole building to be and assuming we are at the coldest temperature now so you will be running at that level at the moment.  also assuming that is all delivered 24/7

 

So 8594 at a COP of 3 for the heat pump, would use 2864W of electricity.  So in a week that would use 2.864 * 24 * 7 = 481kWh.  Then add on hot water heating and "other stuff" and your total usage for the week does not unfortunately look unreasonable.

[canalsiderenovation]

Ah I've found something else now in the handover pack.

 

 

Edited January 15, 2021 by canalsiderenovation

[canalsiderenovation]

Ok so I just spoke to Alto and they told me to take the meter readings from the H/P and immersion and to keep a record of this along with my normal electricity meter reading.

 

So:

HP 11903.98

Immersion 0155.14

Electricity reading 09945.3

 

Reduced all thermostats to 19 degrees and will monitor for a week.

 

[SteamyTea]

Just before I go off to work, thought I would have a look at your local temperatures.

Got some data from Whitchurch, which is fairly close to you I think.

Looked at the highest air temperatures on any given day, and the highest dew point temperatures on the same day.

Then plotted them.  This will give the best case.

Time period is 28/12/2020 to 15/01/2021

 

As the majority of the data points were between 0°C and 4°C, this is about the worse point for an ASHP to be working (there has been a few comments about them freezing up)

 

[canalsiderenovation]

Just now, SteamyTea said:

Just before I go off to work, thought I would have a look at your local temperatures.

Got some data from Whitchurch, which is fairly close to you I think.

Looked at the highest air temperatures on any given day, and the highest dew point temperatures on the same day.

Then plotted them.  This will give the best case.

Time period is 28/12/2020 to 15/01/2021

 

As the majority of the data points were between 0°C and 4°C, this is about the worse point for an ASHP to be working (there has been a few comments about them freezing up)

 

 

Thanks @SteamyTea yes we are in Whitchurch (as long as you have the Whitchurch in Shropshire not any of the others)!

 

Let's see how we get on over the next week and I'll monitor. I wonder if we just have had the house very hot unnecessarily! We haven't got our external wall insulation yet and hopefully once the solar is up and running it will fair better.

 

I need to look at those tarrifs too and work out which is best to move to, especially the one from Octopus which seems to have day rates on a par with others and then the cheap rate between midnight and 4am.