Solar peak law 2026: what the cap costs your German rooftop system
A new 10 kWp system without a smart meter loses about 294 kWh a year to the 60 % cap, or €23. With a smart meter the cap goes, but roughly €166 of payment disappears at negative prices.
Checked by Radif Partners · Editorial policy · How we calculate
What the 60 per cent limit costs your system
Curtailed without a smart meter
294 kWh
| Share of output | 2.8 % |
| Feed-in income lost per year | €23 |
| with smart meter: loss at negative prices | €166 |
The solar peak law (Solarspitzengesetz) is an amendment to the EEG 2023 that took effect on 25 February 2025 and sets two levers for new solar systems below 100 kW. Until a smart metering system with a control box has been installed and tested by the grid operator, a system on the feed-in tariff may export no more than 60 % of its installed capacity (section 9(2) EEG). For a south-facing 10 kWp system in a home using 4,000 kWh, that costs 294 kWh on the national average, 2.8 % of output or about €23 a year. Once the smart meter is in, the cap falls away, but from the following calendar year quarter-hours with a negative wholesale price earn nothing (section 51 EEG). With 24 % of solar output produced in such hours in 2025, that is €166 a year. Section 51a adds half of that time to the end of the 20 years of support. Plug-in solar and systems running before the cut-off date are exempt.
Two levers against the midday peak
The act on avoiding temporary generation surpluses, commonly called the solar peak law, responds to a new problem: on sunny spring days millions of rooftop systems produce more power at midday than the grid can absorb, and the wholesale price drops below zero. In 2025, SMARD recorded 573 such hours. The reform therefore works in two places. First, small systems have their export capped as long as the grid operator cannot control them remotely. Second, payment stops when the power is worth nothing on the exchange, once the system is metered digitally. The two levers never apply at the same time: it is either the cap or the zero rate.
The 60.0 % cap in the wording of the law
Section 9(2) sentence 1 no. 2(b) and no. 3 EEG requires operators of systems below 100 kW on the feed-in tariff (Einspeisevergütung) to limit active power export at the grid connection point to 60.0 % of installed capacity. What counts is the connection point, not the inverter: whatever the house uses or the battery absorbs at the same moment does not count against the cap. A 10 kWp system may therefore export 6 kW and use any amount above that itself. The duty only ends once a smart metering system and control unit are installed and the grid operator has tested control successfully.
In practice, the inverter or an energy manager trims output for a few midday hours on a limited number of days. The simulation with 74 metered households shows how small the loss usually is:
| Case (10 kWp, 4,000 kWh) | curtailed | share of output | loss at current rate |
|---|---|---|---|
| South 30°, no battery | 294 kWh | 2.8 % | €23 |
| South 30°, 5 kWh battery | 286 kWh | 2.7 % | €22 |
| East-west 30° | 85 kWh | 1.0 % | €7 |
| Full feed-in, south | 483 kWh | 4.6 % | €59 |
The battery barely helps, which surprises many owners: it is often already full when the peak arrives, and only reduces curtailment if an energy manager deliberately holds it back until midday. With full feed-in the cap bites harder because no household load absorbs the peak. Size the battery for your evening consumption instead; see battery size.
Zero cents at negative prices
Section 51(1) EEG is brief: for periods with a negative spot price, the reference value falls to zero. Since the cut-off date this applies per quarter-hour and from the very first negative quarter-hour. For systems below 100 kW, however, the zero rate only starts after the end of the calendar year in which the smart meter was installed (section 51(2) no. 1). If yours arrives in autumn, you keep full payment until New Year’s Eve.
On the national average, the 10 kWp system with a smart meter loses €166 a year this way, based on the share of solar output produced in negative-price hours in 2025. At the same time, without the cap, it exports 294 kWh more. The swap does not pay for the owner unless consumption moves; it starts to make sense with a battery, wallbox or heat pump running at midday. Monthly figures and the year-on-year comparison are under negative power prices.
What section 51a gives back
To soften the loss, section 51a EEG extends the payment period. For solar systems, the number of zero-rated quarter-hours counts only half (factor 0.5). The result, called full-load quarter-hours, is added after the regular end as a time allowance, and each month uses up a different number of them according to its typical solar output: a June counts for a lot, a December for little. The extension runs until the end of the month in which the last quarter-hour falls. For your budget, this means today’s loss is partly made up in about two decades, without interest and only if the system is still running.
Who is not affected
- Existing systems: systems commissioned from 1 January 2023 and before 25 February 2025 are not subject to the 60.0 % cap (section 100(3b) EEG), and the earlier version of section 51 still applies to negative prices (para. 46). The same 10 kWp system from 2024 exports 8,936 kWh unthrottled and earns €725 a year at 8.11 ct/kWh.
- Voluntary switch: under section 100(47), the operator of an older system can declare in text form that the new sections 51 and 51a should apply. It takes effect at the earliest from the end of the year the smart meter was fitted; in return, the reference value rises by a fixed premium.
- Plug-in solar: up to 2,000 Wp and 800 VA behind the household meter, neither the cap nor the zero rate applies; see plug-in solar 800 watts.
- Direct marketing: the 60.0 % cap only concerns power on the feed-in tariff; directly marketed systems have other control duties.
And from 2027?
The government draft of the EEG 2027 (printed paper 21/7867) has not been passed. It proposes a permanent cap at 50.0 % for new rooftop systems below 100 kW, even with a smart meter. For systems running by the end of 2026, the draft keeps today’s rules. Details: feed-in tariff 2027.