The Solar Peak Act and Section 51a of the EEG: What Do PV Investors Need to Know Now?
As of February 25, 2025, the feed-in tariff for new photovoltaic systems will be suspended as soon as the market price turns negative—immediately, with no waiting period. This is based on the Solar Peak Act, which revised Section 51 of the Renewable Energy Sources Act (EEG) and created a compensation mechanism through Section 51a of the EEG. For PV investors, this is a key factor in their calculations: in 2025, there were 573 hours with negative electricity prices.
The short answer
The Solar Peak Act (Federal Law Gazette 2025 I No. 51, in effect since February 25, 2025) stipulates that for new PV systems of 2 kWp or more, the feed-in tariff drops immediately to zero when the market price is negative (Section 51(1) EEG)—the previous hourly rule (6, then 4, then 3 hours) no longer applies.
To compensate, Section 51a of the EEG extends the 20-year support period: For photovoltaic systems, lost quarter-hours are calculated using a factor of 0.5 and made up at the end of the term. Systems installed before February 25, 2025, are grandfathered in (Section 100(46) of the EEG).
This article explains what the Solar Peak Act specifically stipulates for PV investors: which systems are subject to the zero feed-in tariff under Section 51 of the EEG, how the compensation mechanism under Section 51a of the EEG recovers the subsidy, what applies to existing systems, and how the loss of revenue can be assessed from an economic perspective. Our guide to negative electricity prices and photovoltaics provides a more in-depth look at the broader market context of negative prices.
1. Why Negative Electricity Prices Are Becoming a Factor in Cost Calculations
The increase follows the expansion of renewable energy: With every additional gigawatt of solar capacity, the supply-demand balance shifts, especially during sunny midday hours. The number of hours with negative prices nearly doubled between 2023 and 2025.
| Year | Negative Price Hours |
|---|---|
| 2023 | 301 hours |
| 2024 | 457 hours |
| 2025 | 573 hours |
| First half of 2026 | about 291 hours (slightly down) |
| Source: Federal Network Agency/SMARD. As of August 2026. | |
At the same time, the first half of 2026 shows a slight decline for the first time, with approximately 291 hours—so the trend is not inevitable, but the price signal remains a structural part of every investment analysis. For investors and PV system owners, it is not the individual event that matters, but the broader context: How much revenue is lost, and how is it offset? The Solar Peak Act addresses precisely this with two interrelated sections—Section 51 (Outage) and Section 51a (Compensation).
2. Solar Peak Act of 2025: What the Law Changes
Simply put, the law pursues four interrelated goals: making the market more flexible and avoiding generation peaks; promoting self-consumption as well as the use of battery storage and smart control systems; advancing the digitization of the power grid through smart meters; and thereby ensuring grid stability in light of the expansion of photovoltaic capacity. The two specific instruments behind this are Section 51 of the EEG for compensation for lost revenue and Section 51a of the EEG for balancing.
The official title is “Act Amending Energy Industry Law to Prevent Temporary Surpluses in Electricity Generation.” It was signed into law on February 21, 2025, promulgated on February 24, 2025 (Federal Law Gazette 2025 I No. 51), and entered into force on February 25, 2025. The Bundestag had approved it on January 31, 2025, and the Bundesrat on February 14, 2025.
| Period | Regulation |
|---|---|
| Effective Date | February 25, 2025 (Federal Law Gazette 2025 I No. 51) |
| Affected Systems | New PV systems starting at 2 kWp (classified by capacity/metering system) |
| New Core Rule | Immediate zero remuneration in the event of a negative market price (Section 51(1) of the EEG) |
| Compensation | Extension of the subsidy period (Section 51a of the EEG), for PV with a factor of 0.5 |
| Grandfather Clause | Systems installed before February 25, 2025, remain subject to the old regulations (Section 100(46) of the EEG) |
| Source: EEG 2023, as amended by the Solar Peak Act. As of August 2026. | |
Act Amending Energy Industry Law: Purpose and Background
Behind this cumbersome title lies a specific goal: to prevent temporary surpluses in power generation. Amid the solar boom, an oversupply of solar energy is meeting low electricity demand—putting pressure on the power grid. Instead of curtailing plants across the board, lawmakers are relying on controllable feed-in: grid operators can reduce the feed-in from controllable plants during periods of overload, remotely via the control box. In this way, the law improves the system integration of renewable energies and grid stability. For investors, this is not an abstract change, but rather the practical framework within which a plant is planned.
3. Section 51 of the EEG: Feed-in Tariff for Negative Electricity Prices — Old 4-Hour Rule vs. New Quarter-Hour Rule
It used to be different. The old version contained a tiered-hour rule: Compensation was only forfeited after several consecutive negative hours. This rule has been tightened over the years—from the original 6-hour rule, to the 4-hour rule, and finally to 3 hours. Short-term price dips thus had no consequences. The Solar Peak Act completely eliminates this buffer for new installations.
Since the German day-ahead market switched to 15-minute contracts, the following rule applies to new facilities: Payment ceases as soon as the market price turns negative in any 15-minute interval. Feed-in to the grid continues—only the payment drops to zero during that quarter-hour. Important: Remuneration that has already been paid out will not be reclaimed; the subsidy never becomes negative—it simply ceases to be paid.
4. Which PV systems are affected: Power classes, smart meters, and intelligent metering systems
The tiered structure under Section 51(2) of the EEG:
- Less than 2 kWp: Exempt until the Federal Network Agency issues a determination pursuant to Section 85(2)(12) of the EEG.
- Less than 100 kWp: The zero-reimbursement rule does not take effect until the end of the calendar year in which the system is equipped with a smart metering system.
- 100 kWp and above: The rule takes effect immediately—smart meters and remote control are already in place here due to existing requirements.
For investor-owned systems in the open-space and commercial rooftop sectors—typically well over 100 kWp and sold directly to the grid—the requirements therefore apply in full from the date of commissioning. Anyone planning a system should factor in a smart meter and control box from the outset: They are prerequisites for accurate billing, participation in the compensation mechanism, and direct sales to the grid. The costs of the smart metering system are subject to the statutory price caps set forth in the Metering Point Operation Act (MsbG) and are billed through the metering point operator. The overarching framework for this is established by the 2026 smart meter mandate.
The 60-percent threshold as a temporary solution for smaller facilities
For new systems under 100 kWp without a smart meter and control box, a feed-in limit of 60 percent of the rated capacity applies on a transitional basis (Section 9(2) EEG 2023, as amended)—a cap on capacity, not on annual output. Once the metering system and control box are installed, the limit is automatically lifted. According to HTW Berlin, the loss in yield ranges from 1.1 to 9 percent, depending on the orientation. This transitional rule does not apply to investor-owned systems over 100 kWp that sell their electricity directly: They are immediately subject to zero remuneration, and the 60-percent limit does not apply to direct sales anyway (Section 21a EEG).
5. Compensation Mechanism under Section 51a of the EEG: Recovering Subsidies
This mechanism makes the effects of the Solar Peak Act predictable: lost feed-in tariffs during hours with negative prices are not lost but are made up for at the end of the term. It works in three steps.
- Step 1 — Collection: Throughout the entire funding period, all quarter-hours during which the applicable value under Section 51(1) has dropped to zero are recorded. The data is sourced from the smart metering system. There is no annual settlement; the quota increases over the entire term.
- Step 2 — Halving: At the end of the 20-year period, the accumulated quarter-hours are multiplied by a factor of 0.5 (Section 51a(2), first sentence, EEG). The result is the full-load quarter-hours (VLVS). This factor applies only to solar power systems; other renewable energy sources are calculated without halving, in accordance with Section 51a(1). The Federal Network Agency may adjust the factor by regulation (Section 85(2)(13) of the EEG).
- Step 3 — Extension: The VLVS quota is deducted on a monthly basis after the subsidy period ends—the subsidy continues until the credit balance is exhausted. This is based on monthly full-load quarter-hours as defined by law.
| Month | VLVS | Month | VLVS |
|---|---|---|---|
| January | 87 | July | 498 |
| February | 189 | August | 453 |
| March | 340 | September | 371 |
| April | 442 | October | 231 |
| May | 490 | November | 118 |
| June | 508 | December | 73 |
| Total | 3.800 | ||
| Source: Section 51a(2), third sentence, of the EEG 2023. The monthly figures reflect the seasonal variation in output. | |||
Calculation Example: How long will the subsidy be extended?
A model example based on 300 hours of negative pricing per year illustrates the scale: 300 hours correspond to 1,200 quarter-hours of downtime per year, which amounts to 24,000 quarter-hours over 20 years. Multiplying this by a factor of 0.5 yields 12,000 full-load quarters of an hour. Divided by 3,800 VLVS per year, this extends the subsidy period by approximately 3.2 years.
6. Grandfathering for PV System Owners: Systems Installed Before February 25, 2025
| Commissioning | Performance threshold | Current regulations | Extension of Section 51a |
|---|---|---|---|
| Starting February 25, 2025 | 2 kWp and above (iMSys classification) | Effective immediately from the first negative quarter-hour (Section 51(1), as amended) | Yes — Section 51a, paragraph 2, factor 0.5 |
| January 1, 2024–February 24, 2025 | 400 kW and up | 3 consecutive hours | Yes — Section 51a(1) (previous version), factor 1.0 |
| January 1, 2023–December 31, 2023 | 400 kW and up | 4 consecutive hours (4-hour rule) | Yes — Section 51a(1) (previous version), factor 1.0 |
| January 1, 2016–December 31, 2022 | 500 kW and above | 6 consecutive hours | No |
| Before January 1, 2016 | No threshold | No reduction in compensation | No |
| Source: EEG|KWKG Clearing House; Section 100(46) of the EEG 2023, as amended; as of August 2026. | |||
Important for investors with rooftop systems: Systems under 400 kW that were commissioned between 2023 and February 24, 2025, were never subject to the old Section 51—they will receive the full feed-in tariff, regardless of electricity prices.
7. Voluntary switch to the new system: + 0.6 ct/kWh
Approval under EU state aid law was granted on September 18, 2025. Whether the switch is worthwhile depends on the individual system—specifically, its exposure to negative prices, the costs of the metering system and control box, and the value of the surcharge. Those who already rely on direct marketing and dynamic rates need the metering technology and stand to benefit twice over. For businesses that are hesitant to make the investment, photovoltaic models as direct investments are also worth considering.
8. Strategic Response to Negative Electricity Prices: Direct Marketing, Self-Consumption, New Opportunities
Three factors determine economic efficiency—metering technology, self-consumption, and storage. They are interrelated and determine the extent to which negative prices affect annual revenue.
Smart Meters and Control Boxes: Technical Requirements
Smart meters and control boxes must be included in the project planning from the very beginning: They provide the billing data, help avoid the 60 percent cap, and are a prerequisite for the compensation mechanism under Section 51a of the EEG. Without this metering technology, neither participation in the feed-in tariff extension nor direct marketing is possible.
Self-Consumption as a Factor in Economic Viability
Using solar power for personal consumption eliminates the need to purchase electricity from the grid—and at commercial rates, this saves many times more than any feed-in tariff. Self-consumption thus remains one of the most cost-effective strategies for PV system owners, regardless of the requirements of the Solar Peak Act.
Battery Storage and Flexibility Options
A battery storage system charges during periods of negative prices and feeds power back into the grid when prices return to positive levels. Dynamic electricity rates, the targeted use of storage systems, and other flexibility options transform the energy system into a source of returns for investors rather than a risk.
Direct Sales and Market Value of Solar Energy
For systems of 100 kWp or more, the path leads to mandatory direct marketing with a sliding market premium (Sections 21 and 21b of the EEG). The reference value for this is the solar market value, which averaged 4.508 ct/kWh in 2025. The article on current direct-marketing prices for PV electricity details how revenues and marketing prices behave in the event of negative prices. The article on negative prices as an investment signal covers the complete revenue and arbitrage calculation for storage systems.
9. Context: Where the EEG 2027 Framework Is Headed
This does not affect existing facilities: Facilities that begin operations by December 31, 2026, will retain the unilateral market premium for 20 years. The reform applies only to new plants, and the Bundestag and Bundesrat have yet to approve it. The status of the legislative process should be reevaluated before any investment decision is made. The compensation mechanism under Section 51a of the Renewable Energy Sources Act (EEG) remains unaffected and continues to make downtime predictable.
10. Conclusion: What Really Matters Now
The Solar Peak Act immediately implemented zero remuneration for new PV systems when prices are negative—but at the same time, it established a clear compensation mechanism through Section 51a of the EEG. For investors, this has three implications. First: Smart meters and control boxes must be included in every project plan from the outset—they are prerequisites for billing, compensation, and direct marketing. Second: The loss of feed-in tariff revenue during hours with negative prices is not lost revenue; rather, it is deferred to the end of the contract term under Section 51a. Third: Those who factor in self-consumption and storage can make the price signal manageable rather than threatening.
Planning a Solar Investment with a Clear Regulatory Framework
Logic Energy designs, builds, and operates turnkey PV systems with lifespans ranging from 20 to 40 years and supports investors from the initial cost analysis through ongoing operations management. The contractual partner for direct investments is mediplan Helm e.K., a partnership with personal liability of the owners.
Frequently Asked Questions About the Solar Peak Act and Section 51a of the EEG
What is the Solar Peak Act, and when does it take effect?
The Solar Peak Act (Federal Law Gazette 2025 I No. 51) is an amendment to the Energy Industry Act (EnWG) and the Renewable Energy Sources Act (EEG) and took effect on February 25, 2025. Since then, for new PV systems of 2 kWp or more, the feed-in tariff is immediately suspended as soon as the market price turns negative for a quarter of an hour. To compensate, Section 51a of the EEG extends the subsidy period.
How does Section 51 of the EEG change the 4-hour rule?
The previous graduated system—under which zero remuneration was paid only after several consecutive negative hours (at times 6, then 4, then 3 hours)—no longer applies to new plants. As of February 25, 2025, pursuant to Section 51(1) of the EEG, every single negative quarter-hour counts. Existing plants retain their respective previous hourly thresholds.
What does the compensation mechanism under Section 51a of the EEG mean?
For every quarter-hour without compensation, the 20-year subsidy period is extended. For photovoltaic systems, the quarter-hours of downtime are calculated as 0.5 times the full-load quarter-hours and deducted on a monthly basis after the subsidy period ends. This allows for the recovery of downtime during periods of negative prices at the end of the term.
Do I have to repay any compensation I've already received?
No. The feed-in tariff drops to zero during negative quarter-hours but never becomes negative. Payments already made remain unaffected. There is no obligation to repay funds—only the entitlement to payment for the affected quarter-hours is forfeited, and this shortfall will be offset later under Section 51a of the EEG.
Does the Solar Peak Act also apply to my existing system?
No. Facilities commissioned before February 25, 2025, retain grandfathering status under Section 100(46) of the EEG with their old hourly thresholds and capacity limits. Operators may voluntarily switch to the new system and will then receive a surcharge of 0.6 ct/kWh on the applicable rate.
How many hours of negative electricity prices have there been recently?
On the day-ahead market, there were approximately 301 hours in 2023, about 457 hours in 2024, and a total of 573 hours in 2025 with negative wholesale prices (Federal Network Agency/SMARD). The first half of 2026 saw a slight decline, with about 291 hours. 573 hours correspond to about 6.5 percent of all hours in the year.
Can Energy Storage and Direct Marketing Solve the Problem?
Partially. A battery storage system charges during periods of negative prices and feeds power back into the grid when prices return to positive levels; self-consumption replaces expensive grid purchases. In direct marketing for systems of 100 kWp or more, the market value of solar power (2025: 4.508 ct/kWh) serves as the benchmark. Both measures reduce the impact of negative prices but do not completely eliminate it.
Sources and Legal Basis
- § 51 EEG 2023 — Reduction of Payment Entitlement in the Event of Negative Prices, accessed August 7, 2026
- § 51a EEG 2023 — Extension of the Feed-in Tariff Period in the Event of Negative Prices, accessed August 7, 2026
- § 9 EEG 2023 — Technical Requirements (60-Percent Feed-in Limit), accessed August 7, 2026
- § 100 EEG 2023 — Transitional Provisions (Grandfathering, para. 46; Voluntary Switch, para. 47), accessed August 7, 2026
- Federal Network Agency / SMARD — Electricity Market Data for 2025 (573 hours of negative prices), January 5, 2026
- EEG|KWKG Clearing House — Reduction in Remuneration in the Event of Negative Prices, Overview of Grandfathering Provisions, accessed August 7, 2026
- pv magazine — The § 51a EEG Compensation Mechanism in Detail, February 7, 2025
- Federal Network Agency — EEG Feed-in Tariffs and Market Premium as of August 1, 2026, accessed August 7, 2026
- Netztransparenz.de — Market Value of Solar Power in 2025 (annual average of 4.508 ct/kWh), accessed August 7, 2026
Edited by Logic Energy. Last updated: August 2026.
