Battery storage and peak shaving, explained

Most commercial electricity bills in northern Europe have two parts. You pay for the energy you use, in kWh, and for the capacity you need, in kW. The capacity part is often set by the single highest fifteen-minute peak in a month, sometimes in a year.

That means a few minutes when the compressors, a furnace and the chargers all start together can cost as much as weeks of steady running. Peak shaving is the job of keeping those few minutes off the grid.

Why one peak can cost you a month

Network operators size the grid for the highest load it has to carry, so they charge for it. If your contracted capacity is 1,500 kW and one morning you draw 1,800 kW for fifteen minutes, many tariffs bill the whole month at 1,800. Exceed it often enough and the operator will ask you to pay for a bigger connection.

How a battery shaves a peak

A battery on site watches the main meter every second. You set a threshold just below the peak you want to avoid. When the site's demand rises above it, the battery discharges exactly the difference. The grid sees a flat line at the threshold; the site carries on as before.

Power and energy are different questions

• Power, in kW, is how deep a peak the battery can cover at once. If your peaks reach 400 kW above the threshold, you need at least 400 kW of battery power.
• Energy, in kWh, is how long it can keep covering. A 400 kW excess that lasts 45 minutes needs 300 kWh, plus a margin for the next peak and for the battery's own losses.
• Both come from your meter data. Half-hourly data is enough to see the shape of a peak; 15-minute data shows it properly.

Stacking the value

A battery that only shaves peaks sits idle most of the day. The strongest cases give it several jobs: storing midday solar that would otherwise be exported cheaply, running the evening shift when grid prices are highest, shaving peaks whenever they come, and holding a reserve to back up critical circuits.

The controls decide, minute by minute, which job matters most. We write that control plan down before installation, so you know exactly how the battery will behave.

What to send us

A full year of 15-minute or half-hourly meter data from your energy supplier, your current tariff and your contracted capacity. With those three, we can show you how many peaks a battery would have caught last year and what they would have saved.