What does a PV battery storage system cost?
A home battery is priced mainly per usable kilowatt-hour of capacity, plus inverter, installation and electrical work. The honest answer is a range, not a single number — so this page shows what each cost block contains and how to check an offer you have been given.
Quotes are built from four blocks: (1) the battery modules, priced per usable kWh; (2) the battery inverter or hybrid inverter; (3) installation — mounting, DC/AC wiring, fuses, meter cabinet work; (4) commissioning, grid registration and, where required, an upgraded meter. Ask every installer to split the offer into these four lines. A price given only as one lump sum cannot be compared with any other offer, and the per-kWh figure you see in advertising almost always refers to the modules alone.
Manufacturers state nominal (gross) capacity, but you can only cycle the usable (net) part. Divide the total offer price by the USABLE kWh, not the nominal kWh, otherwise you will compare a 90 %-depth-of-discharge system against an 80 %-one and reach the wrong conclusion. Also check the warranty: typical lithium home batteries are warranted for a defined number of full cycles or years, with a guaranteed remaining capacity at the end. A cheaper battery with fewer warranted cycles is more expensive per kWh delivered over its life.
Size follows consumption, not the roof. A common rule of thumb for households is roughly 1 kWh of usable storage per 1,000 kWh of annual electricity consumption, capped by what your PV array can actually refill on a normal day. A typical reference case: a 10 kWp PV system with 4,000 kWh annual consumption reaches around 30 % self-consumption without a battery. A battery raises that share by shifting midday surplus into the evening — but only up to the point where the extra kWh sits unused. Oversizing is the single most common way to destroy the economics.
The saving per stored kilowatt-hour is the difference between the retail electricity price you avoid and the feed-in tariff you give up. If you buy at roughly 35 ct/kWh and feed in at roughly 8 ct/kWh (typical German household figures), each self-consumed kWh is worth about 27 ct. Multiply that by the kWh the battery realistically cycles per year — not by its capacity — and compare with the system price. Cycles that never happen because the battery is too big for the PV array earn nothing.
For a company the retail-price spread is usually smaller, so self-consumption alone rarely carries the case. Commercial systems add peak-shaving (cutting the billed demand peak) and, for larger units, market participation — day-ahead arbitrage and grid services. Fraunhofer IEE has argued that more battery storage relieves the German electricity system by billions of euros per year, and an Austrian study reaches a similar conclusion on lasting price-dampening effects — but those are system-level benefits, and only monetise for an individual operator if the system is actually marketed on those revenue streams.
1) What is the price per USABLE kWh, battery modules only? 2) Is the inverter included, and is it a hybrid or a separate battery inverter? 3) How many full cycles are warranted, and what residual capacity at the end? 4) What exactly is in the installation line — meter cabinet, cabling, backup-power switching? 5) Is grid registration and any required metering upgrade included? Two offers that differ by thousands usually differ in items 2 and 4, not in the cells.