A home battery coupled to a photovoltaic installation stores the surplus produced during the day to release it in the evening, at a common capacity of 5 to 15 kWh, for €500 to €1,000/kWh installed and a service life of 10 to 15 years. Control turns on two distinct quantities: capacity in kWh, which fixes how long it can deliver, and power in kW, which fixes the peak it can hold at any given moment. The warranty is always read in years and in cycles, with a minimum remaining capacity, never in years alone, and the usable depth of discharge counts for more than the rated capacity advertised. Before the quote, inverter compatibility is checked against the manufacturer's list, DC voltage, charge and discharge power, communication protocol, failing which the control will not hold over time.
Understanding home batteries and photovoltaic storage
Self-consumption, energy independence, backup: the most common uses
With solar panels, a home battery is mainly used to store the daytime surplus for reuse in the evening. That's the classic self-consumption use case. Some households also want more energy independence, by limiting grid purchases. Finally, there's backup mode, to power a few circuits during an outage, but that's not automatic, it requires compatible equipment and wiring.
Capacity (kWh) and power (kW): sizing without getting it wrong
Capacity in kWh corresponds to the storable energy. Focus on the usable capacity, not just the nominal value. Power in kW corresponds to what the battery can deliver at a given moment. A small capacity with high power can handle peaks, without covering the whole evening. The reverse covers longer, but may be limited for certain appliances.
Efficiency, cycles, depth of discharge: the notions that make the difference
Look at the round-trip efficiency, which measures the losses between charging and discharging. Also check the number of cycles and the allowed depth of discharge. The deeper and more frequently you discharge, the more the battery wears out. A warranty expressed in years and cycles, with a minimum remaining capacity, gives a solid basis for comparison.
Choosing the right battery for a PV installation: on-site criteria
Lithium iron phosphate (LFP) or other technologies: advantages and limits
For residential use, an LFP battery is often chosen for its thermal safety and good cycling performance. In exchange, it stores less energy for an equal volume. NMC batteries are more compact, but require stricter temperature management. On site, focus mainly on the usable depth of discharge, round-trip efficiency, temperature range and warranty (years and cycles).
Inverter and micro-inverter compatibility: points to check before quoting
Before pricing, check the manufacturer's compatibility list. DC voltage, charge and discharge power, communication protocol (CAN, RS485) and updates all affect stability. With micro-inverters, an AC-coupled battery with a control cabinet is often the starting point; otherwise integration quickly becomes unreliable.
Single-phase or three-phase, future evolution: anticipating extensions and resale
Think about the network from the start. On a three-phase supply, a single-phase battery can limit self-consumption and backup capability. Choose a solution that's easy to expand (addable modules) and keep a margin for a future heat pump or electric car. In the event of a resale, a simple, well-documented, standardised installation is reassuring.
Installation and safety: best practices for installing a battery at a private home
Location, ventilation, electrical protection: avoiding common mistakes
Install the battery in a dry, stable, accessible room, away from heat sources and humidity. Respect the manufacturer's temperature range, avoid direct sunlight and keep clear space for ventilation. Fix the unit securely to prevent any tipping. On the electrical side, plan for isolation, suitable protections, earthing and clear labelling at the panel.
Wiring diagrams: AC or DC coupling depending on site constraints
With AC coupling, the battery is added to the panel via a dedicated inverter. This is often the simplest option when retrofitting an existing photovoltaic installation. With DC coupling, the battery connects on the DC side with a hybrid inverter. Efficiency is often better, but DC wiring demands more rigour (lengths, cross-sections, protections, routing).
Commissioning and checks: settings, tests and customer deliverables
At commissioning, set the charge limits, power, schedules and backup mode. Run tests for a grid outage, check that the protections trip correctly and that energy metering works. Hand the customer a user manual, a single-line diagram, the settings applied, and an emergency shutdown procedure.
Grants, VAT and obligations: what could affect battery sales in 2026
Purchase tariff and selling the surplus: what changes the sizing
Since the order of 5 June 2026, there is no longer an investment grant: the surplus is only paid at the purchase tariff (1.1 c€/kWh, indexed by 2% per year). A battery mainly changes the sizing logic. The more you store, the less surplus you sell, and so the less income at the purchase tariff. The right benchmark remains your customer's consumption profile and the eligible PV power. That calculation is quicker to settle when production is estimated roof plane by roof plane and both self-consumption and export are simulated before sizing the storage.
ECO4, the Boiler Upgrade Scheme and special cases: when storage does (or doesn't) fit the framework
On the funding side, storage is often outside the framework. Both schemes primarily target insulation and heating systems. A battery can sometimes fit in via a wider project: for example, load management, whole-house retrofit, or a packaged offer. Check eligibility before quoting.
Insurance, compliance and liability: documents to prepare and points of attention
In 2026, the sale also goes through the paperwork. Require compliant commissioning (NF standard, manual, diagrams). Add the Consuel certificate if required. And on the professional side, secure your ten-year liability insurance (RC décennale) and warranty terms.
