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Home / system #262

Vaillant Arotherm+

Sawtry, Cambridgeshire · Detached · 116 m² · 1983 to 2011 · 7 kW · radiators · installed by JMR Heating and Energy

5 Jan – 4 Feb 2026 (winter reference)

721 hourly rows · MID-class heat meter present: yes
4.10efficiency (COP) over 721 hours, from the heat meter
better than 81% of the metered fleet in January 2026
Electricity used
424 kWh
Heat delivered
1740 kWh (heat meter)
Estimate without heat meter
flow sensor 3.99 · temperature model 4.13
Mean outdoor temperature
4.8 °C · 672 space-heating hours
Flow temperature at 0 °C outside
31.6 °C (curve slope -0.52 per K)
Flow − return while heating
1.7 K
House needs at −3 °C
3.6 kW (unit rated 7 kW) · fit r² 0.47
Hot water
10% of electricity, COP 3.15
warningOnly 1.7 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 day012232026-01-05: 22.9 kWh, outside -1.8 °C2026-01-06: 23.4 kWh, outside -1 °C2026-01-07: 16.5 kWh, outside 3.1 °C2026-01-08: 18.4 kWh, outside 1.9 °C2026-01-09: 19.8 kWh, outside 2.8 °C2026-01-10: 22.1 kWh, outside 0.3 °C2026-01-11: 17.6 kWh, outside 2.9 °C2026-01-12: 8.2 kWh, outside 9.5 °C2026-01-13: 10.4 kWh, outside 7.4 °C2026-01-14: 15.3 kWh, outside 2.3 °C2026-01-15: 8.7 kWh, outside 6.9 °C2026-01-16: 13 kWh, outside 4.8 °C2026-01-17: 11.9 kWh, outside 6.8 °C2026-01-18: 10.3 kWh, outside 6.3 °C2026-01-19: 10 kWh, outside 7.5 °C2026-01-20: 9.5 kWh, outside 8 °C2026-01-21: 10.7 kWh, outside 6.9 °C2026-01-22: 10.8 kWh, outside 7.2 °C2026-01-23: 12 kWh, outside 6.4 °C2026-01-24: 12.1 kWh, outside 5.8 °C2026-01-25: 13.2 kWh, outside 5.3 °C2026-01-26: 14.9 kWh, outside 2.9 °C2026-01-27: 11.1 kWh, outside 5.5 °C2026-01-28: 15.7 kWh, outside 3.9 °C2026-01-29: 16.2 kWh, outside 3.5 °C2026-01-30: 12.7 kWh, outside 5.6 °C2026-01-31: 12.5 kWh, outside 6.6 °C2026-02-01: 10.1 kWh, outside 6.9 °C2026-02-02: 14.1 kWh, outside 6.1 °C2026-02-03: 19 kWh, outside 2.8 °C2026-02-04: 1 kWh, outside 1.7 °Cdaily COP (heat ÷ electricity)1352026-01-05: COP 3.342026-01-06: COP 3.292026-01-07: COP 4.152026-01-08: COP 3.782026-01-09: COP 3.692026-01-10: COP 3.462026-01-11: COP 3.642026-01-12: COP 5.062026-01-13: COP 4.732026-01-14: COP 3.992026-01-15: COP 4.852026-01-16: COP 4.272026-01-17: COP 4.372026-01-18: COP 4.732026-01-19: COP 4.652026-01-20: COP 4.822026-01-21: COP 4.692026-01-22: COP 4.662026-01-23: COP 4.62026-01-24: COP 4.582026-01-25: COP 4.112026-01-26: COP 3.942026-01-27: COP 4.692026-01-28: COP 4.072026-01-29: COP 3.932026-01-30: COP 4.362026-01-31: COP 4.392026-02-01: COP 4.752026-02-02: COP 4.072026-02-03: COP 3.712026-02-04: COP 2.9401-0501-0901-1301-1701-2101-2501-2902-02
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.