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Vaillant Arotherm+ V2

Acton, London · Semi-detached · 128 m² · 1900 to 1939 · 5 kW · radiators · installed by Dwellow

Last 7 days

169 hourly rows · MID-class heat meter present: no
5.03efficiency (COP) over 169 hours, from the heat meter
better than 99% of the metered fleet in January 2026
Electricity used
66 kWh
Heat delivered
334 kWh (heat meter)
Estimate without heat meter
flow sensor 4.38 · temperature model 4.52
Mean outdoor temperature
10.1 °C · 145 space-heating hours
Flow temperature at 0 °C outside
36.9 °C (curve slope -0.44 per K)
Flow − return while heating
1.6 K
House needs at −3 °C
3.1 kW (unit rated 5 kW) · fit r² 0.09
Hot water
19% of electricity, COP 4.45
warningOnly 1.6 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 day05102026-10-31: 5.4 kWh, outside 12.2 °C2026-11-01: 8.5 kWh, outside 10.3 °C2026-11-02: 9.4 kWh, outside 10.1 °C2026-11-03: 9.2 kWh, outside 9.9 °C2026-11-04: 9.7 kWh, outside 9.8 °C2026-11-05: 10.1 kWh, outside 9.9 °C2026-11-06: 9.3 kWh, outside 10.5 °C2026-11-07: 4.7 kWh, outside 6.6 °Cdaily COP (heat ÷ electricity)1352026-10-31: COP 5.112026-11-01: COP 4.992026-11-02: COP 5.082026-11-03: COP 5.082026-11-04: COP 5.042026-11-05: COP 5.032026-11-06: COP 5.172026-11-07: COP 4.510-3111-0111-0211-0311-0411-0511-0611-07
Daily COP needs a heat meter; days without one show electricity only.

The installed heating curve

one heating hourfitted curve50 °C
2030405060456789101112131415outdoor 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.