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I’m glad the cold spell is over!

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Last Post by Nursethescreens 2 hours ago

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Judith

(@judith)

Noble Member Member

Joined: 2 years ago

Posts: 452

Topic starter 11/01/2026 8:15 pm

Just a sigh of relief that the cold spell is over and the COP has gone up from 3.0 to 3.9.

On our worst day on the 5/6Jan the ASHP used 65kWh of electricity producing 177kWh of heat. (DHW in addition), (Vaillant’s readings). This was >75% of our £17 bill for the day. The average temperature for the day was -3.7C with a minimum of -4C most hours, rising to-0.5 C early afternoon.
This compares with £1.50 a day for heating in October.

What was your worst day?

2kW + Growatt & 4kW +Sunnyboy PV on south-facing roof Solar thermal. 9.5kWh Givenergy battery with AC3. MVHR. Vaillant 7kW ASHP (very pleased with it) open system operating on WC

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Mars

(@editor)

Illustrious Member Admin

Joined: 5 years ago

Posts: 3908

11/01/2026 8:32 pm

Thanks for the update, @judith. Cold spells with heat pumps can be brutal, especially with the price of electricity, but thankfully those extremes tend to be short-lived in the UK.

I remember a spell about three winters ago when temperatures really dropped and our 18 kW heat pump was pulling over 110 kWh a day, which at the time worked out at more than £25 per day. Not pleasant, but very much the exception rather than the rule, thank goodness.

This winter we’ve been back on oil, as many here know, after the heat pump packed up in the autumn. The retrofix of the retrofix is planned for late spring, but living with the boiler again has been a reminder of just how different the experience is... constant hot-cold swings around the house, and none of that steady, even comfort you get from a heat pump.

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Nursethescreens

(@nursethescreens)

Active Member Member

Joined: 2 weeks ago

Posts: 3

11/01/2026 9:38 pm

@editor as a reply for this date the 6th of Jan

in order From the Lefthand side .

scop 3.59

0.07 pence KWH used.(7)

The amount of Standard tariff used and cost. 18x0.28=5.04. £5.04

outside temperature ( North facing Sensor ). -3c ( For ASHP )

Temperature of inside North side bedroom . 18c

Temperature in loft. 4c

Temperature in hallway where Thermostat is 19.1

Total KWH used for HW 5.00

Leaving flow temp 37c

Flow rate.6.9l/min

These figures are taken from a rolling spreadsheet which I try and update the same time every day and go from one set point 09.24 to 09.24 ( 24hrs approx )

I do not have an automated system so this is old school drawing information from 2 points .

1. Daikin controller

2. A old weather station sitting on a pile of stuff halfway along my loft! ( the Display unit gives me the North facing bedroom readings ).

3.59		7.00	18x0.28=5.04	-3c	18c	4	19.1c	5.00	37c		6.9 l/m

The cold weather certainly gave my Machine a bit of a workout with at least -6c twice in the last month and day time temps a couple of times 4 degrees and below.

There is loads more information but I don’t want to seem to Geeky!

Richard.

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