Home battery storage is booming. This guide covers AC-coupled vs DC-coupled systems, battery sizing, inverters, safety requirements, MCS certification, DNO notification, and the electrical installation and certification process.
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Written and reviewed by Andrew Moore, founder of Elec-Mate, against BS 7671:2018+A4:2026, IET Guidance Note 3 and the IET On-Site Guide.
The electrical work must comply with BS 7671:2018+A4:2026, and a domestic battery must be located in line with PAS 63100 (Reg 570.6.7.203). The installer notifies the DNO under G98 (up to 16 A per phase) or G99, fits dual AC and DC isolation with warning notices, and issues an Electrical Installation Certificate. MCS certification is needed only if the homeowner wants Smart Export Guarantee payments.
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C_bank = (E_daily × days × (1 + reserve)) / (η × DoD × temp)E_daily= Daily energy consumption (kWh)η= Round-trip efficiency (decimal)DoD= Depth of discharge (decimal)temp= Temperature derating factor1,000+
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Home battery storage is one of the fastest-growing sectors in UK domestic electrical work. Falling battery prices, rising electricity costs, smart tariffs that reward time-shifting, and the growth of solar PV have made battery storage a practical investment for homeowners and a significant revenue stream for electricians.
A home battery stores electricity — either from solar PV panels, from the grid during cheap off-peak hours, or both — and releases it when the household needs it. The system typically consists of a battery unit, an inverter (which may be integrated into the battery or separate), and the electrical connections to the domestic installation.
The electrical installation must comply with BS 7671:2018+A4:2026, the manufacturer installation manual, and the relevant product safety standards. The installer must notify the DNO (Distribution Network Operator) under G98 or G99 before the system is connected to the grid. If the homeowner wants Smart Export Guarantee (SEG) payments, the installer must be MCS-certified.
This guide covers the types of battery systems, sizing, inverter options, safety requirements, MCS certification, and the electrical installation and testing process.
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The fundamental decision in a home battery installation is whether to use an AC-coupled or DC-coupled system. The choice depends on whether the property already has solar PV, the existing inverter type, and the budget.
The battery has its own inverter and connects to the AC side of the installation (typically at the consumer unit). The battery inverter converts DC from the battery to AC for the house, and AC from the grid or solar to DC for charging. This system works with any existing solar PV installation because it operates independently of the solar inverter. It is the standard choice for retrofitting a battery to an existing solar PV system. The downside is slightly lower round-trip efficiency (85% to 90%) because of the additional AC-DC-AC conversion steps.
A hybrid inverter manages both the solar PV panels and the battery on the DC side. Solar energy charges the battery directly in DC, and the inverter converts to AC once for the house. This is more efficient (90% to 95% round-trip) because there are fewer conversion steps. However, it requires a hybrid inverter that is compatible with both the solar panels and the battery. DC-coupled is the best choice when installing solar PV and battery storage together as a new system. It also typically costs less because only one inverter is needed.
| Factor | AC-coupled | DC-coupled |
|---|---|---|
| Round-trip efficiency | ~85% to 90% | ~90% to 95% |
| Inverters needed | Solar inverter + battery inverter | Single hybrid inverter |
| Best for | Retrofit to existing solar PV | New solar + battery install |
| Solar compatibility | Works with any existing inverter | Hybrid must match panels + battery |
| Typical relative cost | Higher (two inverters) | Lower (one inverter) |
For existing solar PV installations with a working string inverter, AC-coupled is almost always the practical choice — replacing a functioning solar inverter with a hybrid inverter just to go DC-coupled rarely makes economic sense. For new installations, DC- coupled with a hybrid inverter is the preferred approach for efficiency and cost.
Correct battery sizing maximises the financial return for the homeowner and avoids overselling or underselling. The key inputs are:
| Battery size | Best-fit household | Primary benefit |
|---|---|---|
| 3 to 5kWh | Low usage, no solar or small array | Off-peak tariff arbitrage only |
| 5 to 10kWh | Typical UK home (8 to 10kWh/day) | Solar self-consumption + tariff shift |
| 10 to 13kWh | Higher usage, 4kWp+ solar | Most daily import avoided, some backup |
| 13 to 20kWh | EV + heat pump, large solar array | Full backup capability, high daytime loads |
For most UK homes, a battery in the 5 to 13kWh range provides the best balance of cost and benefit. Smaller systems (3 to 5kWh) are suitable for tariff arbitrage only. Larger systems (13 to 20kWh) make sense for high-consumption households with solar PV and EV charging.
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The inverter is the brain of the battery storage system. It manages the flow of energy between the solar PV panels (if present), the battery, the house loads, and the grid. The choice of inverter depends on the system configuration:
The inverter must be appropriately rated for the battery capacity and the maximum charge/discharge rate. A 5kW inverter paired with a 10kWh battery can deliver 5kW continuous power — sufficient for most domestic loads. Check the inverter specification matches the household maximum demand during peak periods.
Lithium-ion batteries store significant energy and must be installed with appropriate safety measures. The key safety requirements are:
The installer must follow the manufacturer installation manual in addition to BS 7671. If there is a conflict between the two, contact the manufacturer technical support for clarification. The manufacturer manual takes precedence for product-specific safety requirements; BS 7671 governs the general electrical installation.
For domestic battery installations, BS 7671 Reg 570.6.7.203 explicitly requires compliance with PAS 63100 — the publicly available specification for domestic electrical energy storage systems. PAS 63100 covers suitable location, minimum clearances, ventilation, and fire separation requirements. Installers must consult it alongside the manufacturer instructions when selecting the battery position in a dwelling. Where the battery sits within a wider solar PV and self-generation setup, the A4:2026 requirements covered in our Section 712 and prosumer installation guide also apply.
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Start free trialMCS (Microgeneration Certification Scheme) certification is a quality assurance scheme for renewable energy installers. For battery storage installations, MCS certification matters for two reasons:
Becoming MCS-certified involves joining an MCS-registered certification body (such as NICEIC, NAPIT, or MCS-specific bodies), demonstrating relevant qualifications (including C&G 2399 or equivalent for battery storage), and passing an assessment. The process typically takes 2 to 4 months and involves ongoing compliance costs. For electricians entering the battery storage market, MCS certification is a strong differentiator and unlocks a larger customer base.
The electrical connections for a home battery system must comply with BS 7671 and the manufacturer installation manual. The key installation requirements are:
The cable sizing calculator can be used for the AC cable between the inverter and consumer unit. For DC cables, follow the manufacturer specification — the cable type, size, and maximum length are usually specified in the installation manual.
The electrical installation for a battery storage system must be tested and certified in accordance with BS 7671. The scope of testing includes:
The standard BS 7671 test sequence covers the AC wiring. The DC side and the battery management system (BMS) require additional checks beyond the scope of a standard EIC. Electrical energy storage systems require specialist knowledge, and designers, installers, and inspectors should refer to the IET Code of Practice for Electrical Energy Storage Systems for test procedures, DC earthing arrangements, BMS functional verification, and capacity testing. Key additional checks include DC earth fault loop impedance, a BMS communications and protection function test, and a capacity verification against the rated output.
An Electrical Installation Certificate (EIC) or Minor Works Certificate must be issued for the new circuits. If the work includes a consumer unit modification or new circuits, an EIC is appropriate. The certificate should note the battery storage system and reference the G98/G99 notification. The homeowner needs this certificate for their records, for the DNO notification, and for MCS compliance documentation.
Battery storage installation is a fast-growing market with strong margins. A typical domestic installation (battery, inverter, wiring, testing, and commissioning) is worth £3,000 to £8,000 for the electrical package alone. Combined with solar PV, the total project value can exceed £15,000.
To compete in this market, electricians need to quote accurately, install efficiently, and produce professional documentation. Here is how Elec-Mate helps:
Size the AC cable from inverter to consumer unit with the cable sizing calculator. Automatic voltage drop check and derating for installation method. Get the correct cable size on the survey, not after you have started the installation.
Price the battery storage installation with Elec-Mate's quoting app. Battery unit, inverter, cables, accessories, labour, testing, commissioning, and DNO notification — all itemised with your margins. Professional PDF quote sent to the customer from the survey.
Complete the Electrical Installation Certificate on site after commissioning. AI board scanning, voice test entry, and instant PDF export. Send the certificate to the homeowner and your MCS documentation folder before you leave.
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