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Home / system #1308

Vaillant Arotherm+

Birmingham · Detached · 115 m² · 1940 to 1982 · 5 kW · underfloor · installed by Smart Boiler Company

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
4.89efficiency (COP) over 721 hours, from the heat meter
better than 98% of the metered fleet in January 2026
Electricity used
204 kWh
Heat delivered
999 kWh (heat meter)
Estimate without heat meter
flow sensor 4.91 · temperature model 4.89
Mean outdoor temperature
10.3 °C · 385 space-heating hours · cooling 0 kWh removed (0 kWh electricity), kept out of the COP
Flow temperature at 0 °C outside
25.6 °C (curve slope 0.48 per K)
Flow − return while heating
2.6 K
House needs at −3 °C
1.8 kW (unit rated 5 kW) · fit r² 0.01
Hot water
no hot-water flag in data
warningOnly 2.6 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.
infoUnit is rated 5 kW but the house needs about 1.8 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 day06122026-10-08: 4.2 kWh, outside 11.3 °C2026-10-09: 3.2 kWh, outside 14.2 °C2026-10-10: 4.6 kWh, outside 10.8 °C2026-10-11: 5.3 kWh, outside 10.3 °C2026-10-12: 3.3 kWh, outside 14.2 °C2026-10-13: 2.9 kWh, outside 15.2 °C2026-10-14: 2.9 kWh, outside 12.8 °C2026-10-15: 2.4 kWh, outside 15.9 °C2026-10-16: 2.1 kWh, outside 10.1 °C2026-10-17: 6.8 kWh, outside 8 °C2026-10-18: 6.8 kWh, outside 9 °C2026-10-19: 7 kWh, outside 10.2 °C2026-10-20: 6 kWh, outside 10 °C2026-10-21: 7.7 kWh, outside 7.9 °C2026-10-22: 8.3 kWh, outside 9.3 °C2026-10-23: 7.4 kWh, outside 8.5 °C2026-10-24: 8.9 kWh, outside 9 °C2026-10-25: 9 kWh, outside 9.9 °C2026-10-26: 7.5 kWh, outside 11.1 °C2026-10-27: 5.2 kWh, outside 12.5 °C2026-10-28: 7 kWh, outside 10.6 °C2026-10-29: 5.4 kWh, outside 11.5 °C2026-10-30: 6.5 kWh, outside 10.6 °C2026-10-31: 7.6 kWh, outside 8.9 °C2026-11-01: 12.1 kWh, outside 8.4 °C2026-11-02: 10.2 kWh, outside 7.7 °C2026-11-03: 9.3 kWh, outside 8.2 °C2026-11-04: 10.9 kWh, outside 8.8 °C2026-11-05: 10.3 kWh, outside 8 °C2026-11-06: 9.7 kWh, outside 8.4 °C2026-11-07: 4 kWh, outside 5.6 °Cdaily COP (heat ÷ electricity)1352026-10-08: COP 4.832026-10-09: COP 4.592026-10-10: COP 4.892026-10-11: COP 4.862026-10-12: COP 4.792026-10-13: COP 4.432026-10-14: COP 4.572026-10-15: COP 4.492026-10-16: COP 4.022026-10-17: COP 4.782026-10-18: COP 4.872026-10-19: COP 4.812026-10-20: COP 5.312026-10-21: COP 4.842026-10-22: COP 4.992026-10-23: COP 5.012026-10-24: COP 5.242026-10-25: COP 4.972026-10-26: COP 5.112026-10-27: COP 4.862026-10-28: COP 5.112026-10-29: COP 5.222026-10-30: COP 4.982026-10-31: COP 5.212026-11-01: COP 4.642026-11-02: COP 4.722026-11-03: COP 5.062026-11-04: COP 4.942026-11-05: COP 4.792026-11-06: COP 4.92026-11-07: COP 3.9910-0810-1210-1610-2010-2410-2811-0111-05
Daily COP needs a heat meter; days without one show electricity only.

The installed heating curve

one heating hourfitted curve50 °C
20304050603579111315outdoor 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.