Storage behind the meter.

Industrial grid fees have two parts: an energy charge per kilowatt-hour for consumption and a capacity charge per kilowatt and year for the highest quarter-hourly load of the billing year. Every grid operator sets the capacity charge itself, per voltage level; there is no official national average. Three verified 2026 price sheets show the spread at medium voltage: €148.05/kW/a at Netze BW¹, €132.13/kW/a at SWM Infrastruktur², €105.77/kW/a at Mittelhessen Netz.³ The gap between two grid operators is thus larger than the gap between two voltage levels.

What is measured is the average active power over each quarter-hour; what is billed is the highest of those values in the billing year. A single quarter-hour therefore sets the cost of twelve months. That is why a system that shaves 51 of 52 events is not 98 per cent successful but has failed — miss one event and the old peak applies again. Whether the billing period is the calendar year is set out in your network use contract.

It is not decided by the height of the peak but by its shape: how far above base load it sits, how often it occurs, how long it lasts and how much time is left in between to recharge. One condition is hard — below 2,500 utilisation hours a year the energy charge carries the grid fee rather than the capacity charge, which in the same price sheets falls to €14–35/kW/a¹²³, and peak shaving then saves almost nothing. Whoever draws high power for few hours a year is the wrong case. The tool above shows the order of magnitude on a synthetic load profile; it becomes meaningful with your own.

As large as the year's largest shaving event in energy terms, not the average one. A system sized for the mean is empty at the largest event — and then the peak appears in the bill after all. The ratio of largest to average event is therefore the real design parameter, and it depends on the shape of your load profile, not its height. To that add the difference between usable and installed: depth of discharge, ageing reserve and efficiency all load onto installed capacity.

A rule under section 19(2) StromNEV: anyone who predictably keeps their peak load outside the grid operator's high-load windows can agree a reduced grid fee. It is worth considering for sites whose peaks already fall there or can be moved there — and storage can produce that deliberately. The catch: this mode competes with peak shaving for the same capacity. Which of the two is worth more is a calculation, not a matter of principle, and it comes out differently at every site.

Yes, and usually it makes sense — but as an addition, not a foundation. Capacity left after own requirements can be placed on the energy markets through an aggregator. Two limits: peak shaving takes priority, because one missed event costs more than a trading day earns, and trading raises the cycle count and with it ageing. If a system only adds up through market participation, it is usually in the wrong place at an industrial site.

A standard system follows the grid and shuts down in an outage — it is not an uninterruptible power supply. Grid forming inverters can keep a defined part of the site supplied in island mode; that requires transfer equipment, a protection concept and agreement with the grid operator, and it costs. Whether it pays depends on a number you know and we do not: what an hour of lost production costs. That number belongs at the start of the conversation, not the end.

Usually yes, but more simply than on a greenfield. In commercial or industrial zones storage is as a rule admissible as an ancillary installation; a building application or notification is still needed depending on the state building code, along with a fire safety concept and coordination with the fire service. Connection at medium voltage adds the chain of evidence under VDE-AR-N 4110. Exactly what applies depends on the state building code and the development plan for your site — we settle that before the design, not after.

For load analysis and the business case, reckon in weeks rather than months — provided twelve months of quarter-hourly values are available. From decision to commissioning it is usually 9 to 18 months. The longest single item is rarely construction, but coordination with the grid operator and component lead times. If you have a date by which the system must be running, name it first: it co-determines which technology is even in question.

Technically the system sits behind your existing connection, on the low- or medium-voltage side of your transfer station depending on size. Contractually you have to notify the grid operator; from medium voltage the chain of evidence under VDE-AR-N 4110 with a plant certificate applies. Your contracted capacity stays as it is for now — lowering it is a separate negotiation that only makes sense once the new peak has been demonstrated. What changes immediately is what a single quarter-hour is worth in your bill.