Home battery price glossary
The words on a battery quote, in plain English, each linked to the page that uses it most.
The one to know first
Nominal capacity is the size on the label and the basis of every official price. Usable capacity is what you can actually draw out. Compare quotes with the official figures on nominal kWh, and with each other on usable kWh.
| Divide the price by | Where the figure comes from | Use it to |
|---|---|---|
| Nominal kWh | The label, the quote, the MCS record | Compare with DESNZ's medians (£1,300, £890 or £630 per kWh by size band) |
| Usable kWh | The manufacturer's specification sheet | Compare two batteries with each other |
| Warranted energy | The warranty document (energy or cycles) | Compare what two warranties cover for the money |
- Nominal capacity
- The energy a battery is rated to hold, in kWh: the size on the label. MCS records it for every registered battery, and DESNZ prices every battery per nominal kWh. Read more
- Usable capacity
- The energy you can actually draw out, in kWh, from the manufacturer's specification sheet. Often a little below nominal, because part of the capacity is held back to protect the cells. Read more
- Price per usable kWh
- The installed price divided by the usable capacity. The fairest way to compare two batteries with each other, though not with the official figures. Read more
- Price per warranted kWh
- The installed price divided by the total energy the warranty covers. A way to compare what two warranties are worth for the money, not a measure of savings. Read more
- Median and mean
- The median is the middle value when every installation is lined up by price per kWh; the mean is the plain average. DESNZ publishes both for each size band. Read more
- kW and kWh
- kW measures power, how fast energy flows; kWh measures energy, how much is stored or used. Batteries are sold by kWh, but the network rules look at the inverter's kW. Read more
- Inverter
- The unit that converts between the direct current a battery or panel produces and the alternating current a home uses. Read more
- AC-coupled battery
- A battery with its own inverter, connected on the home's alternating-current side. Added to existing panels, it usually leaves the solar inverter in place. Read more
- Hybrid inverter (DC coupling)
- One inverter that handles panels and battery together. On a retrofit it usually replaces the existing solar inverter. Read more
- Backup (EPS)
- Switching that lets a battery keep some or all circuits running while the grid is down. Not every battery has it, and it is often priced as an extra. Read more
- Round-trip efficiency
- The share of the energy put into a battery that comes back out, from the specification sheet. The rest is lost as heat in charging and discharging. Read more
- Time-of-use tariff
- An electricity tariff with different unit prices at different times of day, which a battery can use by charging when power is cheap. Read more
- Smart Export Guarantee (SEG)
- The arrangement under which suppliers pay for electricity a home exports. Each supplier sets its own rate, which must be above zero. Read more
- Network operator (DNO)
- The regional company that runs the local electricity network and must be told about every home battery. Read more
- G98 and G99
- The two routes for connecting generation and storage. G98: notify within 28 days for small systems. G99: apply before installation for storage over 3.68 kW and most solar-plus-battery systems. Read more
- MCS and MIS 3012
- MCS is the certification scheme for small-scale energy installers and products; MIS 3012 is its standard for battery installations. Certification for panels does not cover batteries. Read more
- PAS 63100
- The 2024 BSI specification, sponsored by DESNZ, for protecting homes against fires in battery installations: where a battery can go and what a location needs. Read more
- REI 30, 60 and 120
- Fire-resistance classes in minutes for walls and floors. PAS 63100 uses them for the separation an indoor or garage battery needs. Read more
- IK10
- The highest impact-protection rating, which PAS 63100 asks for where a battery sits in a garage or beside a driveway. Read more
- Statement of conformity
- The installer's declaration that the installation follows PAS 63100, attached to the electrical installation certificate. Read more
- Energy-saving materials (VAT)
- HMRC's category for items such as batteries and panels whose installation in a home is zero-rated until 31 March 2027 and charged at 5% from 1 April 2027. Read more
- Typical domestic consumption values
- Ofgem's reference figures for annual household use. From 1 July 2026, a medium-use home on a single-rate meter is 2,500 kWh a year. Read more
Sources (page last reviewed 3 November 2026)
- DESNZ: MCS certified domestic battery installation statistics (April 2024 to March 2026 workbook, published 28 May 2026), checked 3 November 2026.
- BSI / DESNZ: PAS 63100:2024, battery energy storage systems in dwellings (PDF), checked 3 November 2026.
- MCS: notifying distribution network operators (G98 and G99), checked 3 November 2026.
- HMRC: VAT on energy-saving materials and heating equipment (Notice 708/6), sections 2.1, 2.3 and 2.19, checked 3 November 2026.
- Ofgem: review of typical domestic consumption values, decision (May 2026; values from 1 July 2026), checked 3 November 2026.
- Ofgem: Smart Export Guarantee (SEG), checked 3 November 2026.
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