Plug-in solar and the meter 2026: old meter, swap, surplus
A plug-in solar kit may run on the existing meter, even an old spinning-disc one, until the metering operator fits a bidirectional meter on its own initiative. Of the 951 kWh from a 900 Wp device, 479 kWh go to the grid unpaid at 2,000 kWh of consumption.
Checked by Radif Partners · Editorial policy · How we calculate
How much your balcony system pushes into the grid
Surplus to the grid
479 kWh
| Share of output | 50 % |
| Payment for it | none (unpaid acceptance) |
| used at home | 470 kWh |
For the electricity meter (Stromzähler) behind a German balcony power plant, three rules of the EEG apply since the Solar Package I. First, under section 10a(3) EEG a plug-in device may run on the existing metering equipment, including an old Ferraris meter with a spinning disc; its readings are presumed correct for billing until the swap, rebuttable only by proof of a technical fault or tampering. Second, under section 10a(2) EEG the metering operator fits the metering point with a bidirectional meter (Zweirichtungszähler) or a smart metering system without you having to order it; the trigger is the check of your data from the Market Master Data Register. Third, the device is assigned to unpaid acceptance (section 8(5a) EEG): the surplus goes to the grid without payment. With 900 Wp tilted 35° south and 2,000 kWh of consumption, that is 479 kWh a year on the German average, 50 % of output. With 2,000 Wp the surplus rises to 992 kWh, and a 2 kWh battery cuts it to 627 kWh.
Which meter you have
German meter cabinets hold three generations. The Ferraris meter has a spinning aluminium disc and a mechanical counter; some have a reverse-running lock (Rücklaufsperre), noted on the rating plate. The modern metering device (moderne Messeinrichtung) is a digital meter with a display that can record consumption and feed-in separately when set up as a bidirectional meter. The smart metering system (intelligentes Messsystem) is a modern meter with a communication unit, the smart meter gateway. Any of the three is fine for a balcony kit; the only question is what it shows.
What section 10a EEG says about the old meter
Until the Solar Package I the rule was: meter swap first, then operation. Since 16 May 2024 it is the other way round. Section 10a(3) EEG allows plug-in devices at the point of supply before a bidirectional meter is installed, using the existing metering equipment. The second sentence is the decisive one: the readings are presumed correct for billing and balancing, at most until the swap, and the presumption can only be rebutted by proof of a technical fault or tampering. A Ferraris meter that runs backwards with surplus is, by this wording, neither faulty nor tampered with; its reading counts as correct. If, however, you deliberately connect more panel output than section 8(5a) EEG allows, you fall outside the rule, because it only applies to plug-in devices within that section.
The swap comes by itself
The procedure is set out in section 10a(2) EEG. You enter the device in the Market Master Data Register, the Federal Network Agency asks the grid operator to check the data, and the metering operator then fits the metering point with a modern meter as a bidirectional meter or a smart metering system. A separate order from you is expressly not needed. The metering operator follows its own rollout planning, so the appointment may take months. Until then the device keeps running on the old meter. Your rights under the Metering Point Operation Act, such as choosing a different metering operator, are unaffected. How the register entry works is explained under register plug-in solar.
Before the swap: record the reading
When the fitter comes, the old meter is removed and billed at its last reading. Photograph the reading yourself on the day of the swap, with the meter number in the picture, and later compare it with the value on the exchange record and your next bill. Pass the reading to your supplier if the metering operator does not. On the new meter you will read two values: consumption, which sets your bill, and feed-in, which only shows how much balcony power you did not use yourself.
How much goes to the grid
| Panel output | 1,500 kWh use | 2,500 kWh use | 4,000 kWh use |
|---|---|---|---|
| 900 Wp | 550 kWh (58 %) | 419 kWh (44 %) | 293 kWh (31 %) |
| 2,000 Wp | 1,105 kWh (52 %) | 895 kWh (42 %) | 675 kWh (32 %) |
The bidirectional meter shows what used to stay invisible: on sunny middays part of the balcony power flows out through the meter, because the household is using less than the panels deliver. The smaller the consumption and the larger the device, the larger the share. Mounted upright, generation is spread more evenly; 900 Wp upright push out only 278 kWh at 2,000 kWh of use. A 2 kWh battery takes most of the midday peak at 2,000 Wp and lowers the surplus from 992 to 627 kWh; whether it pays is worked out under plug-in solar with battery.
Why the surplus earns nothing
Section 8(5a) EEG requires the plug-in device to be assigned to unpaid acceptance (unentgeltliche Abnahme). The grid operator takes the power but pays no feed-in tariff. What counts for you is therefore only what is used behind the meter in your own home. The feed-in register on the bidirectional meter is information, not a credit. If you want to avoid surplus, you can limit it with a battery or a control that matches output to current consumption; the principle is explained under zero-export solar. The Federal Network Agency answers meter questions in its questions and answers on plug-in solar.