Heatproof
Home / system #300

Viessmann Vitocal 150A

Croxley Green · Semi-detached · 164 m² · 1900 to 1939 · 8 kW · underfloor · installed by JMR Heating and Energy

1–31 Dec 2025

745 hourly rows · MID-class heat meter present: yes
4.56efficiency (COP) over 745 hours, from the heat meter
better than 94% of the metered fleet in January 2026
Electricity used
442 kWh
Heat delivered
2013 kWh (heat meter)
Estimate without heat meter
flow sensor 4.60 · temperature model 4.45
Mean outdoor temperature
6.7 °C · 693 space-heating hours
Flow temperature at 0 °C outside
30.5 °C (curve slope -0.25 per K)
Flow − return while heating
1.7 K
House needs at −3 °C
4.3 kW (unit rated 8 kW) · fit r² 0.29
Hot water
no hot-water flag in data
warningOnly 1.7 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 day017332025-12-01: 10.1 kWh, outside 9.3 °C2025-12-02: 12 kWh, outside 7.7 °C2025-12-03: 16.9 kWh, outside 4.8 °C2025-12-04: 16.2 kWh, outside 5.7 °C2025-12-05: 21.7 kWh, outside 4.1 °C2025-12-06: 10.3 kWh, outside 9.4 °C2025-12-07: 8.3 kWh, outside 9.8 °C2025-12-08: 7.4 kWh, outside 11.1 °C2025-12-09: 7.4 kWh, outside 11.9 °C2025-12-10: 10.5 kWh, outside 9.6 °C2025-12-11: 9.5 kWh, outside 8.6 °C2025-12-12: 9.6 kWh, outside 8.8 °C2025-12-13: 18.5 kWh, outside 5 °C2025-12-14: 11.6 kWh, outside 7.7 °C2025-12-15: 9 kWh, outside 9.9 °C2025-12-16: 11.1 kWh, outside 7.8 °C2025-12-17: 19.3 kWh, outside 4.6 °C2025-12-18: 9 kWh, outside 10.1 °C2025-12-19: 14.7 kWh, outside 6.9 °C2025-12-20: 20.1 kWh, outside 4.7 °C2025-12-21: 6.4 kWh, outside 8.3 °C2025-12-22: 6.9 kWh, outside 8.3 °C2025-12-23: 9.9 kWh, outside 5.7 °C2025-12-24: 15.8 kWh, outside 3.8 °C2025-12-25: 18.8 kWh, outside 2.5 °C2025-12-26: 17.6 kWh, outside 3.1 °C2025-12-27: 17.2 kWh, outside 3.7 °C2025-12-28: 18.7 kWh, outside 5.3 °C2025-12-29: 18.4 kWh, outside 4.6 °C2025-12-30: 24.6 kWh, outside 3.2 °C2025-12-31: 33 kWh, outside 0.6 °C2026-01-01: 1.1 kWh, outside -0.2 °Cdaily COP (heat ÷ electricity)1352025-12-01: COP 5.342025-12-02: COP 5.222025-12-03: COP 4.062025-12-04: COP 4.572025-12-05: COP 3.592025-12-06: COP 5.622025-12-07: COP 6.052025-12-08: COP 6.082025-12-09: COP 6.172025-12-10: COP 5.512025-12-11: COP 5.622025-12-12: COP 5.632025-12-13: COP 4.072025-12-14: COP 4.892025-12-15: COP 5.752025-12-16: COP 5.232025-12-17: COP 3.672025-12-18: COP 5.982025-12-19: COP 4.872025-12-20: COP 3.662025-12-21: COP 6.232025-12-22: COP 6.382025-12-23: COP 5.452025-12-24: COP 4.442025-12-25: COP 4.272025-12-26: COP 4.232025-12-27: COP 4.182025-12-28: COP 4.572025-12-29: COP 4.422025-12-30: COP 3.82025-12-31: COP 3.092026-01-01: COP 3.1212-0112-0512-0912-1312-1712-2112-2512-29
Daily COP needs a heat meter; days without one show electricity only.

The installed heating curve

one heating hourfitted curve50 °C
2030405060-3-113579111315outdoor 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.