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Vaillant Arotherm+

Hove, East Sussex · Detached · 118 m² · 1940 to 1982 · 5 kW · radiators · installed by Hartswood

Last 30 days Last 7 days 5 Jan – 4 Feb 2026 (winter reference)1–31 Dec 2025

Last 7 days

169 hourly rows · MID-class heat meter present: yes

4.56efficiency (COP) over 169 hours, from the heat meter
better than 94% of the metered fleet in January 2026

Electricity used: 80 kWh
Heat delivered: 367 kWh (heat meter)
Estimate without heat meter: flow sensor 4.61 · temperature model 4.20
Mean outdoor temperature: 8.8 °C · 75 space-heating hours
Flow temperature at 0 °C outside: 37.5 °C (curve slope -0.54 per K)
Flow − return while heating: 3.8 K
House needs at −3 °C: 8.2 kW (unit rated 5 kW) · fit r² 0.50
Hot water: 24% of electricity, COP 3.57

warningUnit is rated 5 kW but the house needs about 8.2 kW at −3 °C

Expect backup heater use on the coldest days. Improve insulation or draught-proofing before adding capacity.

Day by day

electricity per daydaily COP3.0 floor

Daily COP needs a heat meter; days without one show electricity only.

The installed heating curve

one heating hourfitted curve50 °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.