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Countrypaul wrote: ↑Thu Oct 26, 2023 11:31 am When I was looking at figures for our refurb the degree days base figure always seemed quite arbitrary and yet can have a significant effect on the overall expected energy consumption. For example, a leaky building that is then made airtight will use less energy to heat - seems obvuous but nearly all the calculations you see assume a baseline of 15.5C in the UK. I found this article helpful: https://www.energylens.com/articles/deg ... re-problem - it is from a UK company I believe.

Ken wrote: ↑Thu Oct 26, 2023 12:28 pm

Countrypaul wrote: ↑Thu Oct 26, 2023 11:31 am When I was looking at figures for our refurb the degree days base figure always seemed quite arbitrary and yet can have a significant effect on the overall expected energy consumption. For example, a leaky building that is then made airtight will use less energy to heat - seems obvuous but nearly all the calculations you see assume a baseline of 15.5C in the UK. I found this article helpful: https://www.energylens.com/articles/deg ... re-problem - it is from a UK company I believe.

You do realise that the 15.5C is the outside temp and the starting point for calculating degree days. Basically they assume that at this temp no heating is required due to passive heating from occupants and sun.
I think you need to look more closely at the SAP 2012 calculations which underpin the EPC ratings. Most installers start their quotes off by just using the EPC fig.

The SAP calculations take account of the locality and openings eg chimney, and vents but perhaps not so much leaky doors etc as it assumes these are airtight.

richbee wrote: ↑Thu Oct 26, 2023 10:32 am I'm fairly well on my way down the ASHP rabbit hole - investigating, reading, watching, learning, calculating.....
This thread is intended to document my process - to get helpful advice from those who know more than me - and maybe eventually to help anyone else starting out on their heat pump journey.

We live in an 1830s stone farmhouse in rural Northumberland, currently heated by oil, which is maybe not the best starting point for a heat pump

I got a fairly comprehensive spreadsheet from my neighbour who is doing a whole house refurb from scratch himself, including ASHP.
Having worked through most of the external wall, roof, windows, doors etc to get U values - the excel sheet reckons a heat loss of ~12.5kW on the coldest day, based on internal temperatures of 21 in the living spaces and 18 elsewhere - which seems to be the standard, even though we only tend to have things at 18.
It also works out the annual kWh use of ~30,000kWh heating & hot water, but this is based on 'degree days' which seems to be a slightly old fashioned concept, with no reference to actual room temperatures, only days on which you are likely to need heating (if it is <15.5 degrees outside).

I have a quote from Octopus for £4.6k on top of the £7.5k grant - I'm holding off getting them to survey until I know a bit more and what questions to ask.

I've been reading / watching a fair bit from the Heatgeeks https://www.heatgeek.com/about/ - who have loads of detailed info.
Anyone else know much about them?
Their very rough website quote was much more expensive, at ~£10k on top of the grant!

Joeboy wrote: ↑Thu Oct 26, 2023 12:47 pm

richbee wrote: ↑Thu Oct 26, 2023 10:32 am I'm fairly well on my way down the ASHP rabbit hole - investigating, reading, watching, learning, calculating.....
This thread is intended to document my process - to get helpful advice from those who know more than me - and maybe eventually to help anyone else starting out on their heat pump journey.

We live in an 1830s stone farmhouse in rural Northumberland, currently heated by oil, which is maybe not the best starting point for a heat pump

I got a fairly comprehensive spreadsheet from my neighbour who is doing a whole house refurb from scratch himself, including ASHP.
Having worked through most of the external wall, roof, windows, doors etc to get U values - the excel sheet reckons a heat loss of ~12.5kW on the coldest day, based on internal temperatures of 21 in the living spaces and 18 elsewhere - which seems to be the standard, even though we only tend to have things at 18.
It also works out the annual kWh use of ~30,000kWh heating & hot water, but this is based on 'degree days' which seems to be a slightly old fashioned concept, with no reference to actual room temperatures, only days on which you are likely to need heating (if it is <15.5 degrees outside).

I have a quote from Octopus for £4.6k on top of the £7.5k grant - I'm holding off getting them to survey until I know a bit more and what questions to ask.

I've been reading / watching a fair bit from the Heatgeeks https://www.heatgeek.com/about/ - who have loads of detailed info.
Anyone else know much about them?
Their very rough website quote was much more expensive, at ~£10k on top of the grant!

I would love to dive right in and get a heatpump in Scotland but 30,000kWh hits me as a massive amount of power. So much so that I double checked on Octopus. 2022 we used a combined electric & gas of 14,800kWh (13,500E/1,300G) and that included a large percentage of our 12,000 miles in EV, say 90%+.

I can't get my head around that. We do have the WBS right enough. I assume a WBS and heat pump can both be in the same property? We are reasonably well.insulated but.not to today's standards and its only double glazing.

So far this year we have used 9,000kWh combined fuels and hope to close the year at around 13,000kWh combined incl a year's EV charging. I want someone to tell me what I'm missing, how can 30,000kWh with a machine who's cop is 4+ be possible?

I feel quite thick when it comes to HP's although I already have one for four years out here in Turkey.

richbee wrote: ↑Thu Oct 26, 2023 12:59 pm

Joeboy wrote: ↑Thu Oct 26, 2023 12:47 pm

richbee wrote: ↑Thu Oct 26, 2023 10:32 am I'm fairly well on my way down the ASHP rabbit hole - investigating, reading, watching, learning, calculating.....
This thread is intended to document my process - to get helpful advice from those who know more than me - and maybe eventually to help anyone else starting out on their heat pump journey.

We live in an 1830s stone farmhouse in rural Northumberland, currently heated by oil, which is maybe not the best starting point for a heat pump

I got a fairly comprehensive spreadsheet from my neighbour who is doing a whole house refurb from scratch himself, including ASHP.
Having worked through most of the external wall, roof, windows, doors etc to get U values - the excel sheet reckons a heat loss of ~12.5kW on the coldest day, based on internal temperatures of 21 in the living spaces and 18 elsewhere - which seems to be the standard, even though we only tend to have things at 18.
It also works out the annual kWh use of ~30,000kWh heating & hot water, but this is based on 'degree days' which seems to be a slightly old fashioned concept, with no reference to actual room temperatures, only days on which you are likely to need heating (if it is <15.5 degrees outside).

I have a quote from Octopus for £4.6k on top of the £7.5k grant - I'm holding off getting them to survey until I know a bit more and what questions to ask.

I've been reading / watching a fair bit from the Heatgeeks https://www.heatgeek.com/about/ - who have loads of detailed info.
Anyone else know much about them?
Their very rough website quote was much more expensive, at ~£10k on top of the grant!

I would love to dive right in and get a heatpump in Scotland but 30,000kWh hits me as a massive amount of power. So much so that I double checked on Octopus. 2022 we used a combined electric & gas of 14,800kWh (13,500E/1,300G) and that included a large percentage of our 12,000 miles in EV, say 90%+.

I can't get my head around that. We do have the WBS right enough. I assume a WBS and heat pump can both be in the same property? We are reasonably well.insulated but.not to today's standards and its only double glazing.

So far this year we have used 9,000kWh combined fuels and hope to close the year at around 13,000kWh combined incl a year's EV charging. I want someone to tell me what I'm missing, how can 30,000kWh with a machine who's cop is 4+ be possible?

I feel quite thick when it comes to HP's although I already have one for four years out here in Turkey.

Sorry, just to be clear, the 30,000kWh is heat energy - so if you had a SCOP of 4, it would take 7,500kWh of electricity to run the heating / hot water system.