Cost and ROI

A home battery system is a significant investment. Understanding the upfront costs and the potential long-term return on investment (ROI) will help you decide if a battery is right for your home and budget.

1. Upfront Costs

The cost of a battery system depends on its capacity (kWh) and power output (kW).

  • Small (2kWh - 5kWh): £2,500 – £4,500
  • Medium (5kWh - 10kWh): £4,500 – £8,000
  • Large (10kWh+): £8,000 – £12,000+

Note: These prices typically include the inverter and professional installation.

2. VAT Reduction

Until March 2027, the installation of home batteries is subject to 0% VAT in the UK, provided it is installed as part of a solar system or as a standalone energy-saving measure. This represents a saving of around £1,000 on an average system.

3. Financial Benefits

A battery provides financial returns in three main ways:

Reduced Grid Purchases

By storing your solar energy (or cheap overnight electricity), you avoid buying expensive electricity from the grid during peak times (usually 4pm–7pm). This can save a typical household £300 to £600 per year.

Load Shifting (Arbitrage)

If you don’t have solar, you can charge your battery at night on a smart tariff (e.g., at 7p/kWh) and use it during the day instead of buying at 25p/kWh.

Smart Export Guarantee (SEG)

With a battery, you can choose when to export your electricity. Some suppliers offer higher rates for exporting during peak demand times, allowing you to “sell high” and “buy low.”

4. Calculating Payback

A typical home battery has a payback period of 7 to 12 years. Since most quality lithium batteries are warrantied for 10 years, the system usually pays for itself within its guaranteed lifespan.

Important: When comparing batteries, look at the Cost per kWh of Throughput. This is the total cost of the battery divided by the total energy it is expected to store over its life. LFP batteries usually have the lowest cost per kWh due to their high cycle count.

5. Non-Financial ROI

Not all benefits are monetary. Many homeowners choose a battery for:

  • Backup Power: Protection against local power cuts (requires specific “EPS” wiring).
  • Carbon Reduction: Using more of your own renewable energy directly.
  • Energy Security: Reducing reliance on large energy companies and international markets.