Bill report
House: 160 m² · 1995–2001 · air-to-water, radiators · 2025-10-01 – 2026-09-30 · 10115
1 · Verdict
48 % above the usual range. About 1,464 kWh or 468 € a year more than needed. Implied efficiency 2.03, promised 3.50.
2 · Where every number comes from
| Number | Value | Backed by | Source |
|---|---|---|---|
| Your electricity use | 9,600 kWh | Measured | Your electricity bill or the heat pump's own meter |
| Heated area | 160 m² | Measured | Your input |
| Heating demand | 14,976 to 19,968 kWh | Estimated | Typical value for the building's age class × area (dena, Verbraucherzentrale) |
| Weather factor of the billing period | ×1.04 | Calculated | 3,386 degree days in Berlin against 3,247 on average over the previous ten years (Open-Meteo, ERA5/ERA5-Land (Copernicus); GeoNames) |
| Hot water | 2,000 kWh | Estimated | 12.5 kWh per m² per year, the German building-code reference |
| Usual efficiency (COP) | 2.7 to 3.3 | Compared | Field tests in existing houses (Fraunhofer ISE) and 139 heat-metered homes (HeatpumpMonitor.org, CC BY 4.0) |
| Usual electricity use | 5,144 to 8,136 kWh | Calculated | Heating demand plus hot water, divided by the usual efficiency |
| Implied efficiency of your system | 2.03 | Estimated | Estimated heat demand divided by your electricity use |
| Promised efficiency | 3.50 | Measured | Your quote or subsidy application |
3 · What this report cannot know
- Whether the cause is a setting, the sizing, usage or the device. That needs the system's data or a visit.
- Whether the system is getting worse over the winters. That needs two winters of measurement.
- How much other appliances on the same bill account for, if the heat pump has no meter of its own.
- Whether the area and age class describe the house well; a renovated old house needs less than its year suggests.
4 · Letter to the installer
Dear Sir or Madam,
the heat pump you installed (system at Example Street 1, 10115 Berlin) used 9,600 kWh of electricity in the period 2025-10-01 – 2026-09-30. For a house like ours the usual range from typical values and comparison data is 5,144 to 8,136 kWh. The excess is about 1,464 kWh, roughly 468 € a year. The implied seasonal efficiency is about 2.03; the quote stated 3.50.
I therefore ask you for an operating check of the system: heating curve and flow temperatures, hot-water settings, cycling, backup-heater operation and hydraulic balancing. Please provide the commissioning record, the heat-load calculation and the proof of hydraulic balancing.
I ask for an appointment proposal within 14 days. The analysis behind these figures is attached; it states for every number how it was derived. Should the cause lie within your firm's responsibility, I reserve the right to file a defect notice under the warranty.
Yours faithfully
Example household
Example Street 1, 10115 Berlin
07/11/2026
5 · Next steps
- Send the letter by email or post, attach this report, and wait 14 days for an appointment proposal.
- At the visit, ask for the commissioning record, the heat-load calculation and the proof of hydraulic balancing; have the heating curve, hot water, cycling and backup heater checked.
- After the fix: repeat the free bill check in twelve months with the new bill. The difference is your gain.
- If the installer does not respond or disputes the figures: the expert report from the system's data, co-signed by a licensed expert, 299 €.
Is a bill not enough? Expert report with a licensed expert · 299 € →
6 · Your rights
- Warranty against the installer: usually five years from acceptance (German Civil Code, § 634a).
- If there is a defect, the installer bears the cost of the remedy (§ 635).
- With a BEG subsidy, the promised seasonal efficiency is part of the subsidy file; keep the quote and the records.
Sources: reference values from Fraunhofer ISE field tests, 139 heat-metered homes (HeatpumpMonitor.org, CC BY 4.0) and typical values from dena and Verbraucherzentrale. Weather data by Open-Meteo.com (CC BY 4.0), ERA5/ERA5-Land, generated using Copernicus Climate Change Service information 2026. Postcode centre point: GeoNames (CC BY 4.0). Sources and method →
This report rests on the numbers you entered and on typical values; it is not an expert opinion and not legal advice. An electricity bill does not prove a defect. Price 19 € incl. VAT.