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Home / system #651

Viessmann Vitocal 150A

Tongham, Surrey · Detached · 150 m² · 1940 to 1982 · 16 kW · radiators · installed by Alton & Jones

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

5 Jan – 4 Feb 2026 (winter reference)

721 hourly rows · MID-class heat meter present: yes
3.55efficiency (COP) over 721 hours, from the heat meter
better than 40% of the metered fleet in January 2026
Electricity used
1517 kWh
Heat delivered
5383 kWh (heat meter)
Estimate without heat meter
flow sensor 3.57 · temperature model 3.23
Mean outdoor temperature
5.8 °C · 689 space-heating hours
Flow temperature at 0 °C outside
40.7 °C (curve slope -0.56 per K)
Flow − return while heating
3.6 K
House needs at −3 °C
10.8 kW (unit rated 16 kW) · fit r² 0.16
Hot water
no hot-water flag in data
infoNo configuration faults detected in this window
Keep the current settings. We will alert you if efficiency drifts.
noteOwner’s note on the source site: “No internal controls monitored on this required on Viessmann review also missing booster heater heat”
valueReaching the fleet’s January median (3.69) would have saved about £15 in this window at 0.25 GBP/kWh. An estimate, not a promise.

Day by day

electricity per daydaily COP3.0 floor
electricity, kWh per day049972026-01-05: 97 kWh, outside -0.9 °C2026-01-06: 96.1 kWh, outside 0.3 °C2026-01-07: 71.3 kWh, outside 3.8 °C2026-01-08: 58.7 kWh, outside 4.5 °C2026-01-09: 73.8 kWh, outside 3.3 °C2026-01-10: 87.2 kWh, outside 0.7 °C2026-01-11: 66.3 kWh, outside 4.6 °C2026-01-12: 27.7 kWh, outside 10.2 °C2026-01-13: 26.6 kWh, outside 9 °C2026-01-14: 52.7 kWh, outside 4.2 °C2026-01-15: 37.3 kWh, outside 7.8 °C2026-01-16: 43.1 kWh, outside 6.1 °C2026-01-17: 34.8 kWh, outside 7.4 °C2026-01-18: 33.1 kWh, outside 7.5 °C2026-01-19: 32 kWh, outside 8.6 °C2026-01-20: 37.6 kWh, outside 7.8 °C2026-01-21: 43 kWh, outside 7.4 °C2026-01-22: 35.2 kWh, outside 8.3 °C2026-01-23: 44.5 kWh, outside 6.8 °C2026-01-24: 41.8 kWh, outside 7.1 °C2026-01-25: 41.7 kWh, outside 6.1 °C2026-01-26: 47.5 kWh, outside 5.3 °C2026-01-27: 45.6 kWh, outside 7.2 °C2026-01-28: 56.4 kWh, outside 4.4 °C2026-01-29: 69.2 kWh, outside 3.5 °C2026-01-30: 40.1 kWh, outside 7.1 °C2026-01-31: 41.1 kWh, outside 7.2 °C2026-02-01: 36.6 kWh, outside 7.2 °C2026-02-02: 42.3 kWh, outside 6.4 °C2026-02-03: 54.8 kWh, outside 4.4 °C2026-02-04: 1.7 kWh, outside 3.8 °Cdaily COP (heat ÷ electricity)1352026-01-05: COP 2.542026-01-06: COP 2.482026-01-07: COP 2.982026-01-08: COP 3.372026-01-09: COP 32026-01-10: COP 2.672026-01-11: COP 3.092026-01-12: COP 4.692026-01-13: COP 4.512026-01-14: COP 3.222026-01-15: COP 4.342026-01-16: COP 3.922026-01-17: COP 4.292026-01-18: COP 4.282026-01-19: COP 4.532026-01-20: COP 4.262026-01-21: COP 4.092026-01-22: COP 4.362026-01-23: COP 4.042026-01-24: COP 3.892026-01-25: COP 4.012026-01-26: COP 3.812026-01-27: COP 4.122026-01-28: COP 3.362026-01-29: COP 3.042026-01-30: COP 4.262026-01-31: COP 4.082026-02-01: COP 4.252026-02-02: COP 4.092026-02-03: COP 3.662026-02-04: COP 4.5901-0501-0901-1301-1701-2101-2501-2902-02
Daily COP needs a heat meter; days without one show electricity only.

The installed heating curve

one heating hourfitted curve50 °C
2030405060-5-3-11357911outdoor 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.