$ heat-pump --live
Romsey · Vitocal 200-A 8 kW
I spend my working days looking at other people's heat pump data, so it seemed only fair to publish my own. Everything here comes straight from MID-certified heat and electricity meters on the system, read every 10 seconds by an OpenEnergyMonitor emonHP.
Connecting…
Heat out
–kW
Electricity in
–kW
COP now
–
no live data
Flow / return
–°C
Room
–°C
Outside
–°C
Met Office, hourly
Hot water
–°C
cylinder probe
Efficiency so far
–
since 6 Nov 2026
Last 24 hours · power
Heat outElectricity inHot water run
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Last 24 hours · temperatures
FlowReturnCylinderRoomOutsideHot water run
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Day by day
Heat outElectricity in
The first full day of data lands on 7 November.
The system
- Heat pump
- Viessmann Vitocal 200-A, 8 kW, R290, fitted 1 November 2026
- Replaced
- Samsung 12 kW, vastly oversized for the house
- House
- 1960s semi-detached, 89 m², filled cavity walls, 270 mm loft
- Design
- 5 kW heat loss at −2 °C, 45 °C flow, new radiators
- Hydraulics
- Straight through: no buffer, no low-loss header
- Hot water
- 300 L cylinder, 50 °C, weekly legionella cycle
- Controls
- Viessmann ViCare
- Installer
- Heat Geek
- Monitoring
- OpenEnergyMonitor emonHP: SDM120 electricity meter and Axioma Qalcosonic heat meter, both MID class
Reading the numbers
COP is heat out divided by electricity in: 4 means four units of heat for every unit of electricity.
Totals start at 09:43 on 6 November 2026, when the electricity meter first reported. Shaded bands are hot water runs.