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Daikin Altherma 3

Maidenhead · Semi-detached · 113 m² · 1940 to 1982 · 8 kW · radiators · installed by Octopus Energy Services

5 Jan – 4 Feb 2026 (winter reference)

721 hourly rows · MID-class heat meter present: yes
4.04efficiency (COP) over 721 hours, from the heat meter
better than 79% of the metered fleet in January 2026
Electricity used
418 kWh
Heat delivered
1692 kWh (heat meter)
Estimate without heat meter
flow sensor 4.13 · temperature model 3.82
Mean outdoor temperature
5.9 °C · 614 space-heating hours · cooling 0 kWh removed (0 kWh electricity), kept out of the COP
Flow temperature at 0 °C outside
34.7 °C (curve slope -0.39 per K)
Flow − return while heating
4.3 K
House needs at −3 °C
3.5 kW (unit rated 8 kW) · fit r² 0.47
Hot water
20% of electricity, COP 3.52
infoUnit is rated 8 kW but the house needs about 3.5 kW at −3 °C
Oversizing causes cycling in mild weather. Cannot be fixed cheaply now, but the curve and minimum run time can limit the damage.

Day by day

electricity per daydaily COP3.0 floor
electricity, kWh per day013262026-01-05: 24.7 kWh, outside -0.9 °C2026-01-06: 26.4 kWh, outside -0.8 °C2026-01-07: 16.6 kWh, outside 3.6 °C2026-01-08: 15.6 kWh, outside 4.1 °C2026-01-09: 16.3 kWh, outside 3.4 °C2026-01-10: 23.9 kWh, outside 0.9 °C2026-01-11: 17.6 kWh, outside 3.7 °C2026-01-12: 9.4 kWh, outside 9.9 °C2026-01-13: 9.2 kWh, outside 8.6 °C2026-01-14: 17.8 kWh, outside 3.5 °C2026-01-15: 11.7 kWh, outside 8 °C2026-01-16: 13.6 kWh, outside 6.2 °C2026-01-17: 9.8 kWh, outside 8.1 °C2026-01-18: 9.4 kWh, outside 8 °C2026-01-19: 8.8 kWh, outside 8.7 °C2026-01-20: 10.2 kWh, outside 8.6 °C2026-01-21: 12.5 kWh, outside 7.4 °C2026-01-22: 9.8 kWh, outside 8.4 °C2026-01-23: 12.7 kWh, outside 7.1 °C2026-01-24: 11.5 kWh, outside 7.5 °C2026-01-25: 10.9 kWh, outside 7 °C2026-01-26: 14 kWh, outside 5.7 °C2026-01-27: 12.4 kWh, outside 7 °C2026-01-28: 15 kWh, outside 4.9 °C2026-01-29: 16.5 kWh, outside 4.1 °C2026-01-30: 12.6 kWh, outside 7.2 °C2026-01-31: 10.8 kWh, outside 6.8 °C2026-02-01: 10.2 kWh, outside 7.7 °C2026-02-02: 11.2 kWh, outside 7.3 °C2026-02-03: 15.2 kWh, outside 4.4 °C2026-02-04: 1.8 kWh, outside 2.9 °Cdaily COP (heat ÷ electricity)1352026-01-05: COP 3.132026-01-06: COP 3.062026-01-07: COP 4.042026-01-08: COP 4.042026-01-09: COP 4.062026-01-10: COP 3.282026-01-11: COP 3.542026-01-12: COP 4.852026-01-13: COP 4.712026-01-14: COP 3.552026-01-15: COP 4.612026-01-16: COP 4.172026-01-17: COP 4.262026-01-18: COP 4.532026-01-19: COP 4.562026-01-20: COP 4.682026-01-21: COP 4.392026-01-22: COP 4.672026-01-23: COP 4.492026-01-24: COP 4.352026-01-25: COP 4.42026-01-26: COP 4.342026-01-27: COP 4.562026-01-28: COP 3.912026-01-29: COP 3.832026-01-30: COP 4.372026-01-31: COP 4.142026-02-01: COP 4.52026-02-02: COP 4.382026-02-03: COP 4.262026-02-04: COP 3.6501-0501-0901-1301-1701-2101-2501-2902-02
Daily COP needs a heat meter; days without one show electricity only.

The installed heating curve

one heating hourfitted curve50 °C
2030405060-7-4-125811outdoor temperature, °Cflow temperature, °C
Each point is one hour of space heating. Lower and flatter is cheaper; well-set radiator systems sit around 35–42 °C at 0 °C outside.
Public system published by its owner on HeatpumpMonitor.org. Cycling (starts per hour) comes from the site’s 365-day statistic. Findings use installer rules of thumb; see methodology.