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Home / system #1366

Vaillant Arotherm+

Derby, Derbyshire · Detached · 193 m² · 1940 to 1982 · 10 kW · underfloor

Last 30 daysLast 7 days5 Jan – 4 Feb 2026 (winter reference)1–31 Dec 2025

Last 30 days

721 hourly rows · MID-class heat meter present: yes
4.37efficiency (COP) over 721 hours, from the heat meter
better than 92% of the metered fleet in January 2026
Electricity used
441 kWh
Heat delivered
1927 kWh (heat meter)
Estimate without heat meter
flow sensor 4.50 · temperature model 5.01
Mean outdoor temperature
10.2 °C · 558 space-heating hours
Flow temperature at 0 °C outside
38.9 °C (curve slope -0.97 per K)
Flow − return while heating
1.8 K
House needs at −3 °C
6.8 kW (unit rated 10 kW) · fit r² 0.58
Hot water
18% of electricity, COP 3.49
warningOnly 1.8 K between flow and return
Circulation pump may be set too high or emitters are undersized for the low flow temperature. Ask the installer to check pump speed.

Day by day

electricity per daydaily COP3.0 floor
electricity, kWh per day09192026-10-08: 7.7 kWh, outside 11.3 °C2026-10-09: 7 kWh, outside 13.9 °C2026-10-10: 15.2 kWh, outside 10.3 °C2026-10-11: 17.8 kWh, outside 9.9 °C2026-10-12: 12.3 kWh, outside 13.1 °C2026-10-13: 7.8 kWh, outside 14.8 °C2026-10-14: 12.2 kWh, outside 12.6 °C2026-10-15: 6.3 kWh, outside 15.8 °C2026-10-16: 13 kWh, outside 10 °C2026-10-17: 18.8 kWh, outside 7.8 °C2026-10-18: 17.3 kWh, outside 9.3 °C2026-10-19: 11 kWh, outside 10.9 °C2026-10-20: 11.5 kWh, outside 10.8 °C2026-10-21: 16.7 kWh, outside 8.3 °C2026-10-22: 17 kWh, outside 8.7 °C2026-10-23: 15.1 kWh, outside 8.9 °C2026-10-24: 17.2 kWh, outside 8.8 °C2026-10-25: 17.4 kWh, outside 10 °C2026-10-26: 13 kWh, outside 11 °C2026-10-27: 12.7 kWh, outside 12.9 °C2026-10-28: 14.2 kWh, outside 10.2 °C2026-10-29: 14 kWh, outside 10.7 °C2026-10-30: 17.1 kWh, outside 10.4 °C2026-10-31: 18.7 kWh, outside 8.8 °C2026-11-01: 18.5 kWh, outside 8.3 °C2026-11-02: 18.6 kWh, outside 7.8 °C2026-11-03: 17.9 kWh, outside 8 °C2026-11-04: 15.2 kWh, outside 9 °C2026-11-05: 15.7 kWh, outside 8.3 °C2026-11-06: 15.2 kWh, outside 8.6 °C2026-11-07: 8.8 kWh, outside 5.9 °Cdaily COP (heat ÷ electricity)1352026-10-08: COP 4.152026-10-09: COP 4.22026-10-10: COP 4.372026-10-11: COP 4.292026-10-12: COP 3.962026-10-13: COP 4.192026-10-14: COP 4.262026-10-15: COP 4.132026-10-16: COP 4.612026-10-17: COP 4.282026-10-18: COP 4.322026-10-19: COP 4.512026-10-20: COP 4.672026-10-21: COP 4.492026-10-22: COP 4.432026-10-23: COP 4.472026-10-24: COP 4.482026-10-25: COP 4.392026-10-26: COP 4.392026-10-27: COP 4.32026-10-28: COP 4.422026-10-29: COP 4.482026-10-30: COP 4.362026-10-31: COP 3.872026-11-01: COP 4.352026-11-02: COP 4.422026-11-03: COP 4.452026-11-04: COP 4.532026-11-05: COP 4.492026-11-06: COP 4.612026-11-07: COP 4.3610-0810-1210-1610-2010-2410-2811-0111-05
Daily COP needs a heat meter; days without one show electricity only.

The installed heating curve

one heating hourfitted curve50 °C
2030405060246810121416outdoor 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.