Understanding the energy label of a water heater and the displayed energy class
What the energy label on a water heater is actually for on your jobs
On a job, the energy label acts as your compass. It lets you compare the efficiency of a water heater at an equivalent range without digging into the manuals. It's also a clear way to explain to a client why a heat pump or gas model can control the bill better than a standard tank, for identical use.
Quick reading: where to spot the energy class (A+ to G) and the key information
The energy class reads on the coloured arrow, on the right. Also keep an eye on the draw-off profile (S to XXL), annual consumption in kWh, noise level (for models with a fan) and, depending on the unit, the usable volume. Two water heaters in "the same class" can be very different if the draw-off profile (S to XXL) isn't suited to the use.
What makes the energy class vary: losses, consumption, draw-off profile
The class depends mainly on the tank's static losses (insulation quality), the production efficiency (heating element, burner, heat pump) and the controls. The calculation is based on standardised draw-off profiles. An oversized tank increases losses. An undersized tank triggers the backup more often and degrades the class.
What distinguishes water heaters by energy class (electric, heat pump, solar)
Electric water heater: typical weak points and levers for improvement
An electric resistance water heater is simple, but its energy class often suffers from the tank's static losses and poorly tuned control. The levers: choose a suitable volume, favour a well-insulated tank, set the setpoint around 55°C, schedule heating during off-peak hours, and limit the length of hot-water pipework.
Heat pump water heater: why it often reaches A+ (and its limits)
A heat pump water heater recovers heat from the air via a heat pump. The result: lower electricity consumption and a class often A or A+. Its limit: the real COP drops if the air is cold or poorly renewed. You also need to manage noise, space, maintenance and the electric backup.
Solar water heater: conditions for aiming at a better energy class
A solar water heater can aim for a very good class if the sizing matches the needs. Collector orientation and tilt, sufficient surface area, a suitable tank, and an efficient backup make the difference. The right indicator is a high solar fraction without overheating in summer. To go further on sizing and optimising a solar DHW system, see optimised individual solar water heater.
Choosing a water heater with the right energy class for the dwelling and its uses
Sizing: volume, consumption profile and hot-water comfort
Start with the right volume, otherwise the energy class won't save you. For a storage water heater, aim in practice for 50 to 70 L per person, adjusted for baths, remote work and occupancy hours. Also look at the draw-off profile shown on the label (S to XXL) and choose a comparable energy class for that same profile.
Location and constraints: noise, ventilation, space, drainage
In an apartment, the key issue remains space and access. A heat pump water heater needs air, so a suitable room or an outdoor connection, plus a condensate drain. Avoid placing it right next to a bedroom, since noise quickly becomes noticeable.
Price/performance trade-off: when to aim for A+ and when an intermediate class is enough
Aim for A+ if your needs are regular and high, or if you're replacing an old electric tank. An intermediate class can be enough for a studio, a second home, or limited use, provided you keep a consistent volume and good control. The goal is good comfort, without overpaying for the equipment.
On-the-ground guidance: improving a water heater's energy class in renovation
Reducing losses: pipework insulation, settings, anti-legionella measures
On site, the fastest gain comes from losses. Insulate the hot-water pipes (especially the first few metres), limit unnecessary lengths, and track down recirculation loops running continuously. Set the water heater around 55°C to avoid heating "for nothing", while keeping a periodic temperature boost for anti-legionella prevention as per the manufacturer's instructions.
Optimising control: off-peak hours, monitoring, appropriate temperature
A well-classed water heater is also a well-controlled water heater. Schedule heating during off-peak hours and, where possible, add simple control (energy manager, contactor, or smart control) to match production to actual use. The right temperature is the one that covers the needs, not the one that feels reassuring.
Consistency with the rest of the works: insulation, mechanical ventilation, solar production, heat pump
Think in terms of a "system". With better insulation and a coherent ventilation system, a heat pump water heater can become worthwhile. If solar production (thermal or PV) is planned, plan ahead for storage. And if a heat pump is coming, check the electrical loads and the location to avoid last-minute compromises.
What to know in 2026: compliance, grants and vigilance on quotes
The link between the label, the energy class and the criteria required for grant applications
In 2026, the equipment's energy label (A to G) and the dwelling's DPE speak the same language, but they don't say the same thing. For grants (MaPrimeRénov', CEE), you'll mainly be asked to prove that the installed equipment meets the technical criteria and is installed by an RGE-certified company. A water heater must therefore be chosen and described so it is clearly eligible.
Documents to prepare: proof of product, reference, label, technical data sheet
On the quote, state an exact reference and avoid vague descriptions. Also prepare the supporting documents, often requested before the grant is paid.
- Energy label, manufacturer's technical data sheet, installation instructions.
- Proof of purchase and specifications (brand, model, serial number if available).
- An up-to-date RGE certificate, insurance, and detailed invoices.
- The data sheet or reference for the relevant CEE operation if you're claiming the premiums.
Common mistakes to avoid: energy-class promises, poor sizing, non-compliant installation
No promises about DPE class on a quote. Rejections tend to come from inconsistent sizing, an installation outside the manual's instructions, or missing elements (controls, commissioning). Also stay vigilant about the water heater's electrical connections and protections. To secure the administrative side, also check our guide on the mandatory information on a renovation works quote.
Key figures
efficient HPWH
Class A+
standard HPWH
Class B
electric storage heater
Class C-D
Frequently asked questions
A heat pump water heater is most often eligible for CEE and, depending on the project and the household profile, for MaPrimeRénov' (amounts vary). To secure the application, check the exact eligibility (reference, performance, use) and have the installation carried out by an RGE-certified company, with a detailed quote and invoice.
Pierre-Louis Guhur
CEO of Argile
