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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

1–31 Dec 2025

745 hourly rows · MID-class heat meter present: yes
3.57efficiency (COP) over 745 hours, from the heat meter
better than 41% of the metered fleet in January 2026
Electricity used
1468 kWh
Heat delivered
5245 kWh (heat meter)
Estimate without heat meter
flow sensor 3.60 · temperature model 3.25
Mean outdoor temperature
7.3 °C · 717 space-heating hours
Flow temperature at 0 °C outside
41.2 °C (curve slope -0.28 per K)
Flow − return while heating
3.2 K
House needs at −3 °C
11.2 kW (unit rated 16 kW) · fit r² 0.23
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 £12 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 day048952025-12-01: 38.9 kWh, outside 9.9 °C2025-12-02: 39.5 kWh, outside 8 °C2025-12-03: 57.9 kWh, outside 6.1 °C2025-12-04: 59.3 kWh, outside 6.3 °C2025-12-05: 74.9 kWh, outside 5.6 °C2025-12-06: 36.7 kWh, outside 9.9 °C2025-12-07: 35.1 kWh, outside 11.1 °C2025-12-08: 25.4 kWh, outside 12 °C2025-12-09: 26.2 kWh, outside 12.1 °C2025-12-10: 35 kWh, outside 10.2 °C2025-12-11: 39 kWh, outside 9.3 °C2025-12-12: 35.5 kWh, outside 9 °C2025-12-13: 58.3 kWh, outside 6.8 °C2025-12-14: 47.6 kWh, outside 9 °C2025-12-15: 33.7 kWh, outside 10 °C2025-12-16: 41 kWh, outside 8.5 °C2025-12-17: 71.5 kWh, outside 6 °C2025-12-18: 31.4 kWh, outside 10.7 °C2025-12-19: 53.5 kWh, outside 7.7 °C2025-12-20: 46.2 kWh, outside 6.2 °C2025-12-21: 28.7 kWh, outside 8.8 °C2025-12-22: 24.9 kWh, outside 9.3 °C2025-12-23: 30 kWh, outside 6.6 °C2025-12-24: 49 kWh, outside 4.5 °C2025-12-25: 62 kWh, outside 3.1 °C2025-12-26: 60.1 kWh, outside 3.5 °C2025-12-27: 55 kWh, outside 4.8 °C2025-12-28: 49 kWh, outside 5.9 °C2025-12-29: 58 kWh, outside 4.6 °C2025-12-30: 65.1 kWh, outside 3.1 °C2025-12-31: 95.2 kWh, outside -1.1 °C2026-01-01: 3.9 kWh, outside -1.2 °Cdaily COP (heat ÷ electricity)1352025-12-01: COP 4.212025-12-02: COP 3.92025-12-03: COP 3.122025-12-04: COP 3.42025-12-05: COP 2.912025-12-06: COP 4.212025-12-07: COP 4.322025-12-08: COP 4.482025-12-09: COP 4.682025-12-10: COP 4.122025-12-11: COP 3.982025-12-12: COP 4.122025-12-13: COP 3.222025-12-14: COP 3.682025-12-15: COP 4.312025-12-16: COP 3.962025-12-17: COP 2.922025-12-18: COP 4.492025-12-19: COP 3.592025-12-20: COP 3.742025-12-21: COP 4.432025-12-22: COP 3.992025-12-23: COP 4.042025-12-24: COP 3.632025-12-25: COP 3.272025-12-26: COP 3.392025-12-27: COP 3.482025-12-28: COP 3.742025-12-29: COP 3.442025-12-30: COP 3.082025-12-31: COP 2.472026-01-01: COP 2.9512-0112-0512-0912-1312-1712-2112-2512-29
Daily COP needs a heat meter; days without one show electricity only.

The installed heating curve

one heating hourfitted curve50 °C
203040506070-5-21471013outdoor 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.