Peak shaving with solar batteries
What peak shaving means for UK homes with solar batteries, and how to estimate whether it affects savings or payback.
Key takeaways
- Peak shaving is about reducing grid import during expensive or high-demand periods.
- For most homes, the value depends on the import tariff, battery controls and whether the battery has enough stored energy.
- It is different from simply increasing solar self-consumption, although the two can overlap.
What peak shaving means
Peak shaving means reducing how much power you take from the grid during peak periods. In a commercial setting, that can be about demand charges. In a home, it is usually about avoiding expensive unit rates on a time-of-use tariff.
A solar battery can help if it has stored energy available when the expensive period arrives. If the battery is empty, too small or locked into a different control mode, the benefit will be limited.
Solar self-use and peak shaving are related
Solar self-consumption is about using more of your solar generation at home. Peak shaving is about reducing grid import at particular times. A battery can do both, but the best control strategy may not be identical.
For example, storing midday solar for the evening can increase self-use and avoid peak import. Charging overnight from a cheap tariff can shave an evening peak too, but that stored energy may not be solar-generated.
How to estimate the value
Start with your time-of-use tariff. Work out the price gap between cheap and expensive periods, then estimate how many kWh the battery can reliably shift into the expensive period after losses.
Keep the estimate cautious. Battery usable capacity, discharge power, round-trip losses, winter solar output and household demand all matter. A 5kWh battery doesn't mean 5kWh of useful peak shaving every day of the year.
Questions to ask before buying
Ask whether the battery can be scheduled around your tariff, whether the supplier or aggregator controls it, and whether export payments change if stored electricity came from the grid.
Peak shaving can be a useful extra benefit, but it shouldn't be used to rescue a weak battery quote unless the tariff rules and household data support the claim.
- Can the battery follow my tariff automatically?
- What is the usable capacity, not just the headline capacity?
- What power can it discharge at during the peak period?
- Will tariff rules affect export from the battery?
Sources checked
- Energy Saving Trust battery storage guideConsumer guidance on home battery costs, storage limits and tariff use.
- Ofgem SEG supplier listCurrent SEG licensee list and annual supplier status.