Can Anyone Explain My Gas Bill Power Discrepancy

I’ve been trying to figure out how much my gas / heating / showers were costing me, but I’ve hit a fairly big discrepancy that I can’t explain.

I have a brand new 28kW/h rated boiler, with 98% efficiency rating, and according to the service manual it will consume 28.57kW/h max worth of gas, or 3.02 m^3 per hour.

I have found through measurement of having a 7 minute hot shower that the boiler was running full whack, consuming exactly at the rate claimed by the guide, 3.02 m^3, but this equates according to my bill to be 34 kW/h.

Where is the extra energy going / being wasted?

Boiler Stats Value Units
Gas Max Flow Rate 3.02 m^3/hr
Max Heat In: 28.57 kW/h
Max Heat Out: 28 kW/h
(Calculated Efficiency) 98.0049002450122 %
Meter Readings
Used 12.5 ft^3
Duration 7 min
Metric Conversion 0.35375 m^3
Flow Rate 3.03214285714286 m^3/hr
Gas Qualities / Constants
Calorific Value 39.7
Conversion Factor 1.02264
kW/h / MJ 3.6

kW/h at Max Flow = Max m^3/h (3.02) * Calorific Value (39.7) * Conversion Factor (1.02264) / kWh per MJ (3.6)

kW/h at Max Flow = 34.0578889333333


  1. No comments yet.
(will not be published)