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Setback savings - fact or fiction?

cathodeRay · 2025-02-27T11:24:11Z

This is a renewed attempt to solve the setback riddle - do setbacks save money without compromising comfort? So far this apparently simple question has eluded a confident answer, largely because the empirical results and theoretical predictions do not agree. This means either one of them, or possibly both, are wrong. The initial posts here have been moved from another thread as they no longer related to that thread's title.

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Air Source Heat Pumps (ASHPs)

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cathodeRay

(@cathoderay)

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Topic starter 09/12/2025 1:27 pm

@jamespa — pickling the little grey cells in hopped water is nothing compared to the effects of using AI! The thing that stuck me about the AI response was the Morning Peak (defined rather oddly as 0600-1200, is midday really in the morning peak?) gCO₂/kWh is the same as the overnight (0000-0600) rate, both are said to be 80-100 gCO₂/kWh, which seems rather unlikely to me. Another things is the reliance on using solar to explain differences, when solar generation is typically a rather trivial contributor. Wind generation on the other hand is currently high because of Storm Bram (Bram? Where do they get these names from?):

Midea 14kW (for now...) ASHP heating both building and DHW

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Majordennisbloodnok

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09/12/2025 1:27 pm

Posted by: @jamespa

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…it would be interesting to compare the average carbon intensity by time of day. I cant lay my hand on that statistic but it must exist somewhere!

I’ve been capturing carbon intensity into Home Assistant for quite some time. There was a hiatus with the API that resulted in my having to ditch what I had and start again, but I’ve got all the data for my region since 1st June (hourly readings) which I can send to you if you want.

105 m2 bungalow in South East England
Mitsubishi Ecodan 8.5 kW air source heat pump
18 x 360W solar panels
1 x 6 kW GroWatt battery and SPH5000 inverter
1 x Myenergi Zappi
1 x VW ID3
Raised beds for home-grown veg and chickens for eggs

"Semper in excretia; sumus solum profundum variat"

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cathodeRay

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Topic starter 09/12/2025 1:33 pm

Posted by: @majordennisbloodnok

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which I can send to you if you want.

Or perhaps post something here, suitably anonymised, though we already know is SE England? For folks using ToU tariffs and concerned about their carbon footprint, surely such information is gold dust?

Midea 14kW (for now...) ASHP heating both building and DHW

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Majordennisbloodnok

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09/12/2025 3:35 pm

Posted by: @cathoderay

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Posted by: @majordennisbloodnok

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which I can send to you if you want.

Or perhaps post something here, suitably anonymised, though we already know is SE England? For folks using ToU tariffs and concerned about their carbon footprint, surely such information is gold dust?

No need for anonymisation; SE England is as granular as it gets for that API.

Here's the data.

Carbon Intensity 20250601 to 20251209 SE England.csv

I've just downloaded it from Home Assistant and uploaded as is. Anyone wanting to do any analysis on it will probably have to mess about with the date/times, though; Excel doesn't seem to like ISO standards quite that much.

"Semper in excretia; sumus solum profundum variat"

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