No regulation sets a service life for a water heater. Neither Regulation (EU) No 814/2013, nor Regulation (EU) No 812/2013, nor the French EPC calculation method mentions a duration in years, and the figures in circulation carry no weight anywhere. What can be decided and quantified is the point at which keeping the unit costs more than replacing it. Three criteria settle it, and all three are recorded during a survey: the unit's declared standing loss, the row the assessment method already applies to it, and the compliance of the installation.
What no text says
No service life is set by regulation
The two European regulations that govern water heaters and cylinders set performance levels, not durations. The French assessment method characterises units by geometry, volume and category, never by age. There is therefore no date beyond which a unit becomes non-compliant purely because it is old.
What is dated, on the other hand
One date structures the market: 26 September 2017. Since that day, point 2.1 of Annex II to Regulation 814/2013 has capped a tank's standing loss at 16,66 + 8,33 × V^0,4 watts, which is exactly the upper bound of class C under Regulation 812/2013. Every tank placed on the market after that date is therefore at least class C, which was not the case before.
Why a quoted duration does not replace a measurement
A figure in years aggregates water hardness, setpoint temperature, cycle frequency and installation quality, four parameters that vary widely from one job to the next. It cannot be demonstrated to a hesitant client, and it does not stand up against a cheaper competitor. A standing loss reading, by contrast, compares against a regulatory cap.
First criterion: what the unit dissipates at rest
Standing loss is read, not estimated
Standing loss S is defined by both regulations as the thermal power dissipated by the tank, expressed in watts. It is published model by model in the Commission's EPREL database, together with the volume, which lets you recover the class and compare it against the cap in force. Figures given in kWh per 24 hours on some commercial data sheets are conversions, not the regulatory value.
What a replacement recovers
Class thresholds for a 200-litre tank, calculated from the formulas of Annex II to Regulation 812/2013, and equivalent energy dissipated over 8,760 hours at test conditions.
| Upper bound of class | Standing loss S | Equivalent standing losses |
|---|---|---|
| A+ | 31.8 W | 279 kWh |
| A | 43.9 W | 385 kWh |
| B | 61.4 W | 538 kWh |
| C, regulatory cap since 2017 | 86.0 W | 753 kWh |
| D | 107.0 W | 937 kWh |
| E | 139.7 W | 1,224 kWh |
| F | 169.7 W | 1,486 kWh |
A 200-litre tank sitting at the class F boundary therefore dissipates roughly twice what a compliant new unit does, and more than five times an A+. It is that gap, not the age, that carries the case for replacement, provided the new unit is picked from a catalogue whose technical characteristics are verified rather than from a range name. The full set of eight classes appears in the article on water heater energy class.
The special case of cylinder format
If the room constraint that forced a horizontal unit has disappeared since the original installation, the replacement can also change the format. The gain is then independent of the condition of the unit removed, and it is quantified from the assessment table. The full trade-off is covered in the article on choosing between a vertical and a horizontal cylinder.
Second criterion: what the assessment already counts
The row applied to the unit in place
The French assessment method places every electric cylinder in one row of its storage-loss table, according to geometry and category. A unit whose data plate is no longer legible falls back to the "other or unknown" row, harsher than the category B and C rows, without any actual defect having been observed.
The category that disappears from data plates
On an old unit, the category or star rating is the first thing to fade. Photographing the plate before removal is therefore worth doing even when the unit is going to the skip, because it documents the starting point of the assessment and secures the before-and-after comparison.
What the replacement changes in the assessment
Moving from an "other or unknown" row to a category C row saves 97 kWh a year at 200 litres, without changing format or volume. The calculation and the full table appear in the article on DHW storage losses.
Third criterion: the compliance of the installation
Temperature control
National safety rules cap hot water at the outlets, in France at 50 °C in rooms intended for washing and 60 °C in other rooms. A unit whose thermostat no longer regulates, or whose outlet mixing valve is missing, falls outside that framework. That is grounds for immediate remedial work, regardless of any consideration of age.
The safety group and its drain
The group must remain operable, visible and connected to a drain with an air break. A seized group, a removed drain or a permanent discharge are defects to deal with before any recommissioning, and together on a scaled unit they often tip the trade-off towards replacement.
The electrical supply
Dedicated circuit, protection, earth bonding and accessible means of isolation, in line with the national wiring rules that also set the permitted zones in a bathroom. On a replacement, the condition of the existing circuit is checked before ordering the unit, because reworking the supply changes the price.
Deciding and documenting
The decision grid
- Record the volume, the format, the category and, if the model is identifiable, the standing loss declared in EPREL.
- Compare that standing loss against the cap in force and convert the gap into annual kilowatt-hours.
- Check the three compliance items: temperature control, safety group, electrical supply.
- Price the full remedial work, compliance included, and compare it against replacement rather than against a partial quote.
What gets renewed at the same time
- New safety group and reworked drain, whatever the decision.
- Insulation on the first metres of hot water flow and return.
- Thermostatic mixing valve on the outlet where the store exceeds the limit allowed at the tap.
What goes on file
Photograph of the data plate before removal, reference of the new unit, volume, format, category, declared standing loss and the setpoint as adjusted. That set of documents is what will allow a future assessment to be completed without default values, and what will justify the work in an audit. On protecting the vessel, see also the sacrificial anode in a DHW cylinder.
