The capacity charge and the highest quarter hour

A company on registering capacity metering (RLM metering, where the meter records the power drawn every quarter hour) pays for the energy it consumes, and separately for the highest power it drew from the grid within a billing year. That single quarter hour sets a price component for the entire billing year in which it occurs. Anyone who does not know this principle usually underestimates how much one peak-load moment shapes the whole electricity bill.

RLM metering from 100,000 kWh

Grid operators typically handle connection points with annual consumption up to 100,000 kWh through standard load profiles (SLP), where consumption is estimated from a typical pattern rather than measured. Above that threshold, the load profile is measured every quarter hour: registering capacity metering, RLM metering for short, with 35,040 values a year in total. The switch from SLP to RLM is more than a technical formality. It changes the price structure a business has to plan around.

How the annual peak demand sets the capacity charge

From the 35,040 quarter-hour values of a year, the grid operator identifies the highest measured average, the annual peak demand. That single value, usually in kilowatts, is multiplied by the annual capacity price per kilowatt the grid operator publishes. Under §17(2) StromNEV, the result is the Leistungspreis (capacity charge) share of the grid fees for the billing year in which the annual peak demand occurs, regardless of whether that peak was reached once or repeatedly. A single peak-load moment lasting a few minutes can decide the size of an entire price component.

Why a single event shapes the whole year

This logic sets the capacity charge apart from the Arbeitspreis (energy charge), which applies per kilowatt-hour and spreads across the year. The capacity charge is set by the single worst moment of the year, however low the average is. A business that runs evenly all year but starts all its machines at the same time on one occasion pays for that moment for the entire billing year. This is where peak shaving comes in. A storage system supplies power from its own buffer at critical moments instead of the grid, and so lowers the measured peak.

Energy charge and capacity charge together

The grid fees an RLM customer pays combine an energy charge per kilowatt-hour and a capacity charge per kilowatt of annual peak demand, plus further items such as metering and billing. A low energy charge helps little if the annual peak demand is needlessly high. Conversely, a close look at load peaks often pays off more than a discussion of the energy charge alone, because the capacity charge acts on a single value a business can actively influence.

How a storage system lowers the annual peak demand

A storage system used for peak shaving monitors the power draw continuously and switches in once an agreed threshold is reached. It then supplies power from its own buffer for the duration of the peak, while the draw from the grid is held at the threshold. Because the annual peak demand is formed from the average of a single quarter hour, it is enough to shave the peak over exactly that period. A short but very high peak calls for a different balance of power and energy content than a longer, more moderate one. That distinction only emerges from a company’s own annual load duration curve, not from a general rule.

It also matters that the storage system’s control is synchronised to the same quarter-hour rhythm the grid operator measures on. A controller that reacts too late, or only detects the threshold near the end of a quarter hour, can no longer catch a peak effectively. The specification of a system meant for peak shaving should therefore list response time and measurement interval as separate requirements.

Atypical and intensive grid use under §19(2) StromNEV

§19(2) StromNEV opens two routes to an individual grid fee that can relate to a storage system. The first applies to a connection point whose annual peak load foreseeably and materially differs from the simultaneous annual peak load of all draws on the grid, so-called atypical grid use. The second applies to intensive grid use with a high and steady load, measured by utilisation hours (annual consumption divided by annual peak demand) above certain thresholds. A storage system deployed specifically for peak shaving changes exactly the figures both rules are based on. It can improve or worsen the case for an individual fee, depending on how it is operated. That is a reason to know the utilisation hours and the load profile precisely before a storage decision, not after.

For intensive grid use, the ordinance grades the individual fee by the number of utilisation hours in the year: the higher the hours, the greater the possible reduction. Peak shaving that lowers the demand value without changing annual consumption to the same extent raises the calculated utilisation hours, and so can shift the classification into a more favourable tier, or block it, depending on the starting position. Both directions are possible, which is why any assessment has to start from the actual load profile and should never be assumed in general.

How high a company’s annual peak demand actually is, when it occurs, and how stable it is year to year is what a load-profile analysis shows. As of September 2026.

Sources

1. §19(2) StromNEV, gesetze-im-internet.de
2. §17(2) StromNEV, gesetze-im-internet.de
3. Stromnetz Berlin GmbH, "Standardlastprofile ab 01.01.2025" (in German; 100,000 kWh threshold for standard load profile/RLM as current grid-operator practice)