Home battery storage that turns daytime solar into evening savings.

How home battery storage works

Home battery storage keeps electricity for later. By day it stores solar power your home is not using; in the evening it runs the kettle, cooker and lights instead of the grid. On a time-of-use tariff it can also charge from the grid overnight, which matters in a Scottish winter.

It has three parts: battery modules that store direct current, an inverter that converts it to the alternating current your home uses, and a management system controlling charging and temperature. Many home batteries use lithium iron phosphate (LFP) cells.

What size home battery do you need?

Size a battery to what you use between sunset and the cheap overnight rate, not to your annual bill. Ofgem's typical home uses about 2,500 kWh a year, roughly 7 kWh a day, and your smart meter data shows how much of that falls in the evening. On a quote, check:

• Usable capacity (kWh), which can be less than the headline size.
• Power (kW): too little, and the oven and an electric shower together still pull from the grid.
• What refills it: a battery your panels only fill in summer, or that the overnight window cannot fill, adds cost without savings.

We size it from your meter data at survey.

What a home battery runs in a power cut

A standard grid-connected battery switches off in a power cut: inverters disconnect when the grid fails, so they cannot feed lines engineers may be working on. Backup has to be designed in:

• Backup circuits: an emergency power supply (EPS) output feeds chosen circuits such as the fridge, lights, router and boiler controls.
• Whole-home backup: switchgear isolates the house from the grid, then the battery runs whatever its power rating can carry.

The Tesla Powerwall, for example, offers partial or whole-home backup when fitted with its matching switchgear. Either way, keep a reserve: a battery that empties itself every evening cannot help in an overnight cut.

Battery brands we install

We're a Tesla Powerwall certified installer, EcoFlow PowerOcean partner, and also fit GivEnergy and Sigenergy systems. We recommend brand based on use-case, not commission — and where the shortlist comes down to the two flagship systems, our SigenStor vs Tesla Powerwall 3 comparison works through the published specifications rather than the sales pitch.

Specifying a premium whole-home system? As a SigEnergy installer in Scotland, Ecoaim designs and fits the SigenStor 5-in-1 — solar inverter, battery, EV DC charger and AI energy management in one stackable tower. Already on an EcoFlow PowerOcean? See the upgrade from EcoFlow to SigEnergy.

Octopus Flux: turn your battery into a profit centre

The Octopus Flux tariff (and similar time-of-use tariffs) pays more for export in the 16:00–19:00 peak than it charges to import overnight: in South Scotland, 27.19p/kWh for peak export against 14.27p/kWh to import between 02:00 and 05:00 (correct as of 6 October 2026). Charge cheap, sell at peak. Systems that expand a module at a time suit this best, because you can add capacity once you have seen a winter of real peak usage — the SigenStor stacks in 6.02 or 9.04 kWh steps for exactly that reason. We configure every install to maximise tariff arbitrage from day one.

Which tariffs make a home battery pay

A battery earns on the gap between cheap and dear electricity. On a flat tariff that gap is small. In our Central Belt worked example, a 5 kWh battery adds about £118 a year to a 4 kWp solar system: welcome, but rarely enough alone. The case rests on tariffs that price the day differently:

• Cheap overnight import: charge off-peak and run the house through the evening peak, the main way a battery earns in winter.
• Time-of-use import and export: Octopus Flux prices both by time of day, and was open to new customers with solar and a battery when we checked on 6 October 2026.
• Peak-weighted export: Prime Outgoing Octopus pays 16p/kWh between 4pm and 7pm and 9p/kWh outside that window, against 12p flat on standard Outgoing (correct as of 6 October 2026).

Rates differ between Octopus's South and North Scotland regions: compare the best tariffs for solar and battery homes, read how Octopus Flux works, and if you still have an Economy 7 or Economy 10 meter, start there.

Home battery storage with or without solar panels

Panels are optional. A standalone battery charges in a cheap overnight window and covers the dear hours, which can suit a flat or a listed home, and since 1 February 2024 it has qualified for 0% VAT. With panels, spare daytime solar does most of the charging in brighter months; see solar panels with battery storage for designing the two together.

Retrofit or new install?

Both work. AC-coupled batteries retrofit onto most existing solar systems with a 1-day install on site. We handle the DNO paperwork (a G98 notification, or a G99 application approved before install if the combined inverter capacity goes over 16A per phase), electrical compatibility, and warranty transfer.

An AC-coupled battery brings its own inverter and leaves the solar one alone; if that solar inverter is ageing, a hybrid unit running panels and battery together can make more sense. Either way, the combined inverter capacity can push a G98 system over 16 amps per phase, and a G99 application then needs approval before the battery goes in. Which suits your system is set out on add a battery to existing solar panels.

Batteries behave very differently on a business site, where peak-shaving against a capacity charge often beats tariff arbitrage outright. If you are storing for a commercial load rather than a household one, our commercial solar panel installers team sizes the battery against your half-hourly profile alongside the array — see the commercial solar installers UK guide for how the two are modelled together.

How long a home battery lasts, and what the warranty covers

Expect a battery to outlast its warranty but not your panels. Which? notes battery systems often come with a 10-year warranty while panels can last 25 years or more, so budget to replace the battery at least once. Read the warranty, not the brochure:

• Capacity: the minimum share of usable capacity the warranty guarantees by the end of its term.
• Throughput: whether it caps the total energy cycled through the battery, for example when a third party controls it or it is used for grid trading.
• Connection: whether the cover can be cut short if the system spends long periods offline.

Where a home battery can go, and how to keep it safe

A 2020 UK government safety review reported few recorded fires involving domestic lithium-ion storage. Siting still matters: BSI's PAS 63100:2024 says the best place is outside the home, away from habitable rooms. Among the places it rules out:

• bedrooms, and cupboards that open into them
• escape routes, including hallways, landings and stairs
• lofts, roof spaces and voids
• outside walls within 1 metre of a door, window, vent or escape route
• within 2 metres of stored flammable materials or fuel tanks

A battery in a store cupboard needs its own smoke alarm or multi-sensor detector, interlinked with the rest of the house; Scottish homes have needed interlinked alarms since February 2022 anyway. Outdoors, check frost tolerance: one common LFP module is rated to charge only between 0°C and 50°C. Modules are heavy: around 48 kg for one 5 kWh unit.

See the new-build case study →

What home battery storage costs in Scotland

Our typical installed prices with new panels: 4 kWp of solar plus a 5 kWh battery is usually £10,500–£13,500 (£6,500–£8,500 without the battery), and 8 kWp with a 10 kWh battery is £15,000–£19,000. All include 0% VAT, which covers home batteries with or without solar until 31 March 2027.

For a standalone or retrofit battery the price depends on the inverter route and wiring; as a market guide, Which? puts home batteries at anything from under £2,000 to £10,000. Get your free quote for your home.