Another ashp/electricity usage question

[Jvh2012]

Firstly, is my consumption high please? Our consumption fluctuates so much even when we’re not at home (2 week holiday early may)  and I am so confused we have an ecodan ashp.

 

I have attachedenergy-consumption 4.xlsx our usage and hope someone can help with whether this is normal usage please.

 

we live in a 4 bed detached house, new build With all energy efficient appliances, epc b and air tightness test provided a result of 4.2. 
 

tia 

Edited December 13, 2022 by Jvh2012

[crooksey]

50kw total consumption for the whole house seems about right in this cold weather (12/12) for a heat pump and all other appliances. My heat pump alone uses this much in this weather.

[SteamyTea]

1 hour ago, crooksey said:

50kw

kWh I suspect.

50 kW would blow the main fuse on a single phase installation.

[Ralph]

I don't think it looks horrendous but It would be useful if you could separate out your ASHP usage and check your flow temps and weather compensation. That has made a difference to mine.

I have noticed that there is big difference in KWh usage for the ASHP when the outside temp gets below freezing. I think my ASHP burned an extra 10KWh on a -5^oC day compared to when it was 5^oC. The weather compensation ups the flow temp on those days and you do notice it.

As a very rough comparison I've divided my total usage into the seasons and averaged the usage per day. Winter is based on the last week when it's been -8^oC  so I'm hoping it will work out much less than the below.

I work from home and we keep it pretty warm in the house.

 

Season	Average KWh Per Day
Winter	40
Spring	11
Summer	10
Autumn	16

 

 

[ReedRichards]

34 minutes ago, Ralph said:

I have noticed that there is big difference in KWh usage for the ASHP when the outside temp gets below freezing. I think my ASHP burned an extra 10KWh on a -5^oC day compared to when it was 5^oC. The weather compensation ups the flow temp on those days and you do notice it.
 

 Even if you had a fixed flow temperature without weather compensation, you would see a big difference between -5^oC and 5^oC outside.

[Jvh2012]

How do I check my flow temps and weather compensation sorry?

[Jvh2012]

Am I missing something then? In our old house we didn’t use anywhere near as much as this (boiler) we seem to be using a lot more whereas we were sold on ashp due to having an energy efficient house we should save a lot of money, (ignoring price increase) we are using a lot more energy out bills are looking to be £600 this month alone! 

[Roger440]

6 minutes ago, Jvh2012 said:

Am I missing something then? In our old house we didn’t use anywhere near as much as this (boiler) we seem to be using a lot more whereas we were sold on ashp due to having an energy efficient house we should save a lot of money, (ignoring price increase) we are using a lot more energy out bills are looking to be £600 this month alone! 

 

I was pondering this only last weekend as i wonder what to do with the heating in the new (to me) house.

 

These kind of numbers say oil is much cheaper. Never mind when the cap on energy is removed in April. You look to be paying 38p per Kwh.

 

Any idea what efficiency the heat pump is running at? Do you have that data?

[ProDave]

55 minutes ago, Roger440 said:

These kind of numbers say oil is much cheaper. Never mind when the cap on energy is removed in April. You look to be paying 38p per Kwh.

At present gas in in the region of 11p per kWh and electricity abut 33p per kWh, so a heat pump achieving a COP of 3 will cost the same to run as a gas boiler.

 

What are the present prices of oil per kWh? @SteamyTea ?  (Boilerjuice suggests about 90p per litre so what's that per kWh?)

 

I get the impression some people are "selling" an ASHP as a super cheap means of heating.  They are not.  Set up properly with a properly designed install they can offer heating to an all electric house at comparable costs to mains gas.  They won't improve on the cost of mains gas in many situations.  They also give environment benefits as the raw energy use and CO2 emissions are lower.

[SteamyTea]

3 minutes ago, ProDave said:

What are the present prices of oil per kWh? @SteamyTea ?  (Boilerjuice suggests about 90p per litre so what's that per kWh?)

There are about 9.5 kWh of thermal energy in a litre of diesel.

So 9.5p/kWh.

If the boiler can deliver at an average of 85% efficiency, then that is 11p/kWh.

So a heat pump needs to deliver at just over CoP of 3.

[TonyT]

If you are on a cheaper night time tariff, it will be most cost effective compared to gas, particularly if you can heat during the cheap time period

 

 

[SteamyTea]

1 minute ago, TonyT said:

If you are on a cheaper night time tariff

After EDF sending out silly numbers, my bog standard, quartly billing, by cash/cheque, standard variable rate, in the most expensive place (SW), night rate (or in other words, the most expensive contract you can get) is 15.37p/kWh (before VAT).

Personally I think that is pretty good considering my storage heaters are 35 years old and have never had any maintenance, not even a fuse changed.

Did have to change the water cylinder a few years back, less than £300 with new elements and thermostats.

So maintenance less than a tenner a year.

[Roger440]

8 minutes ago, SteamyTea said:

There are about 9.5 kWh of thermal energy in a litre of diesel.

So 9.5p/kWh.

If the boiler can deliver at an average of 85% efficiency, then that is 11p/kWh.

So a heat pump needs to deliver at just over CoP of 3.

 

Beat me to it. 

 

But confirming that currently, its the cheapest heating source (leaving wood out of it for the moment)

 

Is a COP of 3 remotely realistic at sub zero temps?

[ProDave]

10 minutes ago, SteamyTea said:

There are about 9.5 kWh of thermal energy in a litre of diesel.

So 9.5p/kWh.

So if you feed that oil into a generator that achieves 30% efficiency then you self generate electricity at 31p per kWh

 

Not such a stupid idea then?

 

But if you can self generate at small scale for 31p per kWh why is wholesale electricity even at it's capped price ABOUT 33P?

[ADLIan]

I’ve done numerous energy assessments over the last few years using ASHP - they became popular as the COP made building reg compliance, based on CO2 emissions, easier. Downside was the running cost which is reflected in the SAP energy rating. I would imagine that a badly designed and/or commissioned system, perhaps with COP of 2 or less, would be a lot more expensive to run than gas.

[SteamyTea]

18 minutes ago, ProDave said:

But if you can self generate at small scale for 31p per kWh why is wholesale electricity even at it's capped price ABOUT 33P?

So many reasons.

In all honesty, you will struggle to generate at 31p/kWh as that is just a small part of the OPEX.

We could work out a price including the CAPEX and a truer OPEX.

But it will be more than 33p/kWh.

Adding in thermal energy recovery may change the numbers though.

 

[SteamyTea]

28 minutes ago, Roger440 said:

Is a COP of 3 remotely realistic at sub zero temps?

I would think it is a bit hard, probably achievable with a, and we have to say it again, properly sized and operated air to air heat pump.

 

Thing is, not worth basing the whole running the cost on a few very cold days.  If we did that, we would never have a spare room (mine has been used twice in the last 9 years), or a large car.

Edited December 14, 2022 by SteamyTea

[Ralph]

51 minutes ago, ProDave said:

I get the impression some people are "selling" an ASHP as a super cheap means of heating.  They are not.  Set up properly with a properly designed install they can offer heating to an all electric house at comparable costs to mains gas. 

I think this key issue with them. By utility bills for my 160m2 house are less than I was for a 70m2 flat with a gas boiler that was built in the 80s. It's about the house as a whole not just the heating system

[SteamyTea]

27 minutes ago, Ralph said:

It's about the house as a whole not just the heating system

Well said.

 

Just seen my coffee drinking mate who is convinced that an oil filled electric radiator is going to be cheaper than the electric panel heaters he currently has.

He will see them as a success as, by the time he has fitted them, the outside are temperature will be 8⁰C higher.

He thinks that the oil acts the same as the bricks in a storage heater. 

He likes Facebook and is a complete twat most of the time.

[Roger440]

56 minutes ago, SteamyTea said:

I would think it is a bit hard, probably achievable with a, and we have to say it again, properly sized and operated air to air heat pump.

 

Thing is, not worth basing the whole running the cost on a few very cold days.  If we did that, we would never have a spare room (mine has been used twice in the last 9 years), or a large car.

 

But even at a COP of 3, its still cheaper to use oil.

 

And thats with subsidised electricity prices. Oil if a free market. Once the energy cap is removed the OP might be paying nearer £1000 a month.

 

My current large, 4 bed semi, part of which has completeley uninsulated walls (solid) is using 1800 litres a year for heating and hot water . Has an EPC of D. Pessimistally, oil is £1 a litre. Thats £1800. A year. £150 a month, average.

 

The OP is doing £600 a MONTH. OK, the average is lower, but even so.

 

Am i missing something?

 

Obviously gas is working out similar, but i dont have it, so its not an option.

 

 

[Roger440]

53 minutes ago, Ralph said:

I think this key issue with them. By utility bills for my 160m2 house are less than I was for a 70m2 flat with a gas boiler that was built in the 80s. It's about the house as a whole not just the heating system

 

Yes, but you have reduced the heat demand. If your reduced demand house had the same gas boiler as your flat, guess what, it would cost less. 

 

Drives me bonkers when you keep reading that the ASHP is more efficent, but you need to insulate properly first. Insulating is always a good idea. That how you reduce the heat load. It will be cheaper to heat than a poorly insulated house, regardless of the heat source.

[Roger440]

1 hour ago, SteamyTea said:

I would think it is a bit hard, probably achievable with a, and we have to say it again, properly sized and operated air to air heat pump.

 

Thing is, not worth basing the whole running the cost on a few very cold days.  If we did that, we would never have a spare room (mine has been used twice in the last 9 years), or a large car.

 

Rather depends where you are. With your location, i agree. Not so much elsewhere in the UK.

[ReedRichards]

8 minutes ago, Roger440 said:

 

But even at a COP of 3, its still cheaper to use oil.

 

When I installed my heat pump two years ago I was buying electricity for less than 13p per kWh and the average price I had paid for heating oil over the previous two years had been 45.2 p per litre.  With these numbers I expected the heat pump to be cost competitive with oil - and I think it was for the first year.  Now electricity costs me 33.67 p per kWh whilst heating oil, currently is less than 90p per litre, I understand.  So now my heat pump is probably cost competitive with mains gas but heating oil is the cheapest fuel you can get.  Who knows what the situation will be like in another two years.  

[SteamyTea]

17 minutes ago, Roger440 said:

But even at a COP of 3, its still cheaper to use oil.

 

And thats with subsidised electricity prices. Oil if a free market. Once the energy cap is removed the OP might be paying nearer £1000 a month

Pretty close at CoP 3. The difference is probably lost in statistical noise.

 

I would not be basing a long term space heating decision on today's skewed prices. 18 months ago the market was totally different.

What we do know is that in the medium term we are heading for electrification, no getting away from that.

 

[Roger440]

8 minutes ago, SteamyTea said:

Pretty close at CoP 3. The difference is probably lost in statistical noise.

 

I would not be basing a long term space heating decision on today's skewed prices. 18 months ago the market was totally different.

What we do know is that in the medium term we are heading for electrification, no getting away from that.

 

 

You raise a valid point. But what do you base the decision on?

 

I dont want to find myself in the position of the OP, especially when "support" for bills ceass, as it inevitably must.

 

Oil prices are at an all time high, and its STILL cheaper than the alternative, electricity. 

 

Unless you see electricity coming down substantially? 

 

I will soon need to make some decisions which i need to live with long term. I cant afford the kind of numbers the OP is seeing, and i dont want to be cold. What to do?