Heat pump quote

QrizB

BuildTheWall said:

.Its strange that they estimate about 11500kwh used by gas, but i get just 4200kwh working backward based on my bills. I turn on heating only absolutely necessary, which would be the biggest factor for the difference, but I assume they have estimated based on worst case basis and also that heat pump works continously?

Their estimate is based on maintaining a constant indoor temperature (of probably 21C) all year around, and on supplying enough hot water for a fully occupied house (2 people per bedroom, I think?). If you keep your house cooler and have a smaller household, your energy use will be commensurately less.

BuildTheWall

QrizB said:

BuildTheWall said:

.Its strange that they estimate about 11500kwh used by gas, but i get just 4200kwh working backward based on my bills. I turn on heating only absolutely necessary, which would be the biggest factor for the difference, but I assume they have estimated based on worst case basis and also that heat pump works continously?

Their estimate is based on maintaining a constant indoor temperature (of probably 21C) all year around, and on supplying enough hot water for a fully occupied house (2 people per bedroom, I think?). If you keep your house cooler and have a smaller household, your energy use will be commensurately less.

Thanks, that makes sense. I do now see that they have assumed 21C in the ground floor and 18C first floor. 

BuildTheWall

Reed_Richards said:

I agree completely with the comments by @matelodave but here is an alternative calculation/estimation.

Take the tariff that you pay per kWh for electricity and divide that by 3 then divide that number by the tariff you pay per kWh for gas.  If the number is less than 1 then it should be cheaper to run a heat pump.  If the number is greater than 1 then gas may be cheaper to run.

I suspect that you will find the number you get is close to one, which means there would not be a big difference in running costs.  And the calculation assumes that you want the same amount of heat from your heat pump as from your gas boiler, that your gas boiler is 100% efficient (likely to be nearer 90%) and that your heat pump gives you an average 3 kWh of heat for every 1 kWh of electricity (which you should comfortably achieve, but more easily if you opt for "Eco").

By the way, I am on an EV tariff which means that, currently, the average cost of my electricity is 19.05 p per kWh.  And I heat my hot water during the cheap rate hours which means that the cost of my hot water is much cheaper than if I had gas.    

I'll be moving to IOG from Sep, therefore I can assume 20p on average as without battery, only a part of space heating and hot water heating can be done during the off peak? Then the number is close to one as you estimated. But if I assume electricity cost of 7p once a battery is installed, heat pump is much cheaper. 

matelodave

As said above, the system will be specified against MCS requirements which make assumptions about temperatures in each of the rooms and the volume of hot water that your house (not you as a person) will require over an average year with an assumed outside temperature.  

This will calculate out as a heat requirement to satisfy those requirements and should provide you with the correct sized heatpump, radiators and hot water tank. 

However if you are happy to sit around a candle to keep warm only on a Saturday night when its snowing outside and take cold showers then you wont need anywhere as much heat as someone who wants a toasty house 24/7 and ten hot showers or baths a week.

stripling

@BuildTheWall
but I assume they have estimated based on worst case basis and also that heat pump works continously? 
While it looks increasingly a poor return financially, the comfort and convenience of having constant warm temperature is making it attractive as I can avoid partner getting annoyed for not turning on heating often.

Also, Octopus estimate on a 50° design temp but if you can over size your radiators you run it on a much lower design temp which is more efficient and cheaper. Mine runs well on a 40° design temp even when several degrees below freezing outside.  I have a 6kw Daikin but I pushed the radiators well over spec (do you have the radiator schedule from Octopus yet?) I'm not convinced by your thinking it's a 'poor return' because if you go the whole enchilada with solar etc., you will be very well set up and 'future-proofed'. 

The heat is lovely, it doesn't feel like 'heating' it's just 'there' and not dry either. That was one of the things that first impressed me about heat pumps when my daughter got one. What size heat pump have 🐙 suggested for you? 

@BuildTheWall
"This is my worry. Ordering an electric hob and the installer finds something missing and that requires further spending."

Do you have an electric oven? Is there a fuse labelled in the fuse box? Is your cooking 'built-in' or free standing? If the latter, you can see by pulling out the cooker and looking behind for a wired-in box. 

The Octopus (unofficial) heat pump Facebook group is friendly and supportive - good for questions and learning. The Renewable Heating Forum is also excellent.
[Text removed by Forum Team]

BuildTheWall

stripling said:

@BuildTheWall
but I assume they have estimated based on worst case basis and also that heat pump works continously? 
While it looks increasingly a poor return financially, the comfort and convenience of having constant warm temperature is making it attractive as I can avoid partner getting annoyed for not turning on heating often.

Also, Octopus estimate on a 50° design temp but if you can over size your radiators you run it on a much lower design temp which is more efficient and cheaper. Mine runs well on a 40° design temp even when several degrees below freezing outside.  I have a 6kw Daikin but I pushed the radiators well over spec (do you have the radiator schedule from Octopus yet?) I'm not convinced by your thinking it's a 'poor return' because if you go the whole enchilada with solar etc., you will be very well set up and 'future-proofed'. 

Interesting. They didnt give me an option to oversize probably thought it'll get expensive and will put me off. 
This is the schedule I received. 

stripling said:

 What size heat pump have 🐙 suggested for you? 

Its Daikin 6kW and 180L cylinder.

Reed_Richards

BuildTheWall said:

Its strange that they estimate about 11500kwh used by gas, but i get just 4200kwh working backward based on my bills. I turn on heating only absolutely necessary, which would be the biggest factor for the difference, but I assume they have estimated based on worst case basis and also that heat pump works continously?

The MCS evaluation is based on maintaining constant room temperatures 24/7.  I think those temperatures are:
21 C for living areas, 22 C for bathrooms and 18 C for bedrooms.  

stripling

BuildTheWall said:

stripling said:

@BuildTheWall
but I assume they have estimated based on worst case basis and also that heat pump works continously? 
While it looks increasingly a poor return financially, the comfort and convenience of having constant warm temperature is making it attractive as I can avoid partner getting annoyed for not turning on heating often.

Also, Octopus estimate on a 50° design temp but if you can over size your radiators you run it on a much lower design temp which is more efficient and cheaper. Mine runs well on a 40° design temp even when several degrees below freezing outside.  I have a 6kw Daikin but I pushed the radiators well over spec (do you have the radiator schedule from Octopus yet?) I'm not convinced by your thinking it's a 'poor return' because if you go the whole enchilada with solar etc., you will be very well set up and 'future-proofed'. 

Interesting. They didnt give me an option to oversize probably thought it'll get expensive and will put me off. 
This is the schedule I received. 

stripling said:

 What size heat pump have 🐙 suggested for you? 

Its Daikin 6kW and 180L cylinder.

Same as me.  Great bit of kit. 
Your radiator schedule looks a bit odd. What's happening in the living room? The two suggested don't add up to the heat loss. 

What are you going to do in the bathroom? 

stripling

@BuildTheWall
18 C for bedrooms.  

You can argue for bigger radiators if you are using any bedrooms for offices - 21° c (you don't have to keep the rooms at that temp).  I managed to get nearly all my radiators increased in size because I have patchy cavity wall insulation. 

NedS

Go as big as you can for all radiators. The larger the rads, the lower the flow temps you can run to achieve the same heat output, and hence the lower your running costs. For our install (not with Octopus), we replaced every radiator in the house for the maximum K2 size the space could reasonably accommodate rather than simply designing for a flow temp of 50C (or whatever). As a result, we ran at flow temps of ~32-35C for much of last winter, which is a lot more efficient than 40C or 50C.