Home Battery Storage

No. A battery pays back two ways. With solar, it captures surplus you'd otherwise export at 5-15p and lets you use it at 28-30p later, lifting self-consumption from around 40% to 70-80%. Without solar, it charges from a smart time-of-use tariff in a cheap overnight window and runs your home through the evening peak. Both work. The right answer depends on your tariff and when you actually use electricity. See our battery worth-it guide for the full maths.

Any tariff with a meaningful gap between off-peak and peak rates. The most common in 2026 are Octopus Go (5-hour overnight window at around 8.5p, especially good for EV charging), Octopus Cosy (off-peak windows in the morning and afternoon at around 13p, designed around heat pump load), and Octopus Agile (half-hourly variable pricing, best with an automated battery scheduler). EDF, OVO and others run similar smart tariffs. Ofgem maintains a neutral overview of smart and time-of-use tariffs. The differential matters more than the supplier name. We size your battery against your chosen tariff so the daily cycle pays back.

Only if it's specified for backup. By default, batteries disconnect when the grid drops, because of G98/G99 anti-islanding regulation. Three options change that. EPS (Emergency Power Supply) keeps a pre-wired essentials circuit live: lights, fridge, sockets, broadband. Available as an add-on EPS box on Fox ESS systems. Whole-home backup uses the Tesla Backup Gateway 2 to switch the entire consumer unit to battery power, transparent to you. Any Powerwall 3 backup, essentials or whole-home, needs the Gateway, which adds hardware and circuit work to the install. Tell our team backup matters before your install date so the right hardware and circuits get specified.

For most retrofits, AC coupling. An AC-coupled battery sits alongside your existing solar inverter and charges from any spare power on your house circuit, so the panels and inverter stay as they are. DC coupling replaces the inverter with a hybrid model and ties the battery directly to the solar DC side, which is slightly more efficient (around 5%) but a bigger job. We default to AC coupling on retrofits unless your existing inverter is at end of life or the efficiency gain pays for the swap. We confirm during the quote.

Most UK 3-bed homes are well served by a 10 kWh battery. With an EV, the question is whether you charge the car off the battery or off the off-peak tariff directly. Usually the latter, since EV charging happens in the same overnight window the battery wants to fill. A 10-13 kWh battery covers the rest of the household. With a heat pump, larger battery sizing helps because you want to bank cheap-rate power to cover the evening heating peak. We typically size 13-20 kWh, often paired with Cosy or a similar tariff. Sizing is a quote-stage conversation.

We notify your Distribution Network Operator (DNO) that the battery is being installed. For most domestic batteries on a single-phase supply, this is a G98 notification, which is a post-install notification. Larger systems above the G98 threshold need a G99 application before the install, and the DNO has up to 65 working days to respond. Battery-only is usually simpler than solar+battery because there's no generation export application required. We handle all the paperwork.

Yes. The battery and inverter you install today work with panels added later. Tesla Powerwall 3 has a built-in solar inverter, so panels connect directly. Fox ESS systems use a hybrid inverter that's already designed to take a solar input. The main extra at solar-add time is the panels, mounting, and an MCS submission for the Smart Export Guarantee. If you know solar's likely within a few years, mention it at the quote stage so we size the inverter accordingly.

Modern lithium iron phosphate (LFP) batteries are rated for around 6,000 charge cycles, which works out to roughly a decade of cycling once a day. The standard manufacturer warranty is 10 years and guarantees the battery will hold at least 70-80% of its original capacity at the end of that period. After the warranty most batteries continue running with reduced capacity rather than failing outright. UKEM adds a 2-year workmanship warranty on top of the manufacturer cover.

Standalone home battery installs typically run from around £4,000 (Fox ESS EP6 at 5.76 kWh) up to £12,000+ (Tesla Powerwall 3 at 13.5 kWh with whole-home backup). The price covers the battery, hybrid inverter where required, isolators, wiring, commissioning, MCS paperwork and DNO notification. A retrofit to existing solar takes around a day. Get a fixed, personalised price through our online quote tool.

Most battery-only installs take around a day on site. No scaffolding, no roof access, no DNO solar generation application. The engineer mounts the battery (typically in a utility room, garage, or outside), wires it into your consumer unit through an isolator, commissions the system, and walks you through the app. Quote to install is usually 3-5 days for a standard retrofit. Powerwall 3 with whole-home backup adds half a day for the Backup Gateway and circuit reconfiguration.

Yes. Home batteries are eligible for our 0% interest finance over 36 months, with no deposit required. Longer terms up to 15 years are available from 9.9% APR Representative. Finance is arranged through FCA-authorised lenders. UKEM acts as a credit broker, not a lender. Most households structure repayments so the monthly cost lines up roughly with their time-of-use tariff savings. See our finance page for how options are structured.