Operating a photovoltaic system requires additional electricity meters. In addition to the electricity drawn from the grid, you also need to record the yield and the amount of electricity fed into the grid. In this article, we will show you which photovoltaic meters you need and what function they perform.
First things first
For photovoltaics you need the following meters:
- reference counter: Measures the amount of electricity consumed.
- feed-in meter: Measures the amount of electricity fed into the grid.
- bidirectional meter: Combines consumption and feed-in meters in one device.
- yield counter: Measures the electricity generated by the PV system.
- Smart Meter: An intelligent system that measures and stores both grid consumption and feed-in and yield.
feed-in meter
With a feed-in meter The amount of electricity fed into the grid by a photovoltaic system is recorded. This is because the vast majority of photovoltaic systems are not operated exclusively to produce electricity for their own use.
In order to have enough electricity available around the clock to cover your own needs, you would need to have an extremely large electricity storage facility. In most cases, this is not economical,
which is why either no solar storage or a relatively small storage unit is used.
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At times when more solar power is generated than can be consumed or stored, the excess electricity is fed into the power grid.
Since the amendment to the Renewable Energy Sources Act in 2009, the grid operator has been obliged to purchase electricity in this regard. The corresponding amount of electricity is recorded using a feed-in meter and can then be billed to the grid operator.
Feed-in meters should be fitted with a backstop and are usually installed in the meter box. However, this is not mandatory.
Feed-in meters can either be rented from the energy supplier or purchased by the customer. When purchasing such a meter, the operator of the solar system is responsible for properly calibrating the device. With rented meters, however, calibration and maintenance are carried out by the electricity supplier.
reference counter
A consumption meter records the amount of electricity that a consumer draws from the power grid. This is a normal electricity meter, like the one found in every private household.
Depending on the model, the meter measures the amount of electricity purchased from the supplier mechanically or electronically. The meter reading is taken at the end of the billing period.
While mechanical meters have to be read on site, many electronic meters can be evaluated wirelessly. Direct access to the meter box is therefore not necessary in such cases.
If you have a PV system with zero feed-in you only need one consumption meter and one yield meter. In the case of stand-alone systems, only one yield meter or no meter is necessary, since the yield can be read off modern inverters.
bidirectional meter
A bidirectional meter combines the functions of a feed-in and a consumption meter. It therefore records both the electricity fed into the grid by the photovoltaic system and the electricity taken from the grid. Compared to these two devices, a bidirectional meter takes up less space.
However, private customers cannot purchase this meter. Instead, they rent it from their electricity provider. There is usually an annual fee
of around 40 euros as rent. The costs for maintenance and calibration of the meters are often already included in this price.
The disadvantage of using a bidirectional meter is that it remains the property of the electricity provider. Therefore, the meter must be replaced if the electricity provider is changed. In addition, the annual rental is higher in the long term than the cost of a theoretical purchase.
yield counter
The yield meter measures all the electricity that a photovoltaic system produces and not just the portion that is fed into the public grid. It serves as proof of the solar power that is consumed by the system itself. It is relevant for tax purposes, as sales tax or, in the case of small businesses, income tax, must be paid on the system's own consumption. The yield meter has a backflow preventer so that the inverter's own consumption is not taken into account. It is always the property of the system operator.
The income tax on the solar income generated will no longer apply with the new tax relief from January 1, 2023. This applies to all private PV systems on one's own property with a size of up to 30 kWp for single-family homes and up to 15 kWp per residential unit for multi-family homes.
Smart Meter
A Smart Meter is an intelligent measuring system that uses a communication network to send and receive data. It consists of a digital meter and a communication module, the so-called smart meter gateway. The meter measures and stores both grid consumption and feed-in and yield. The gateway transmits the data between the consumer and the grid operator. Smart meters are part of the digitalization of the energy transition and are already mandatory for PV systems with a nominal output of over 7 kWp. In this case, you do not need the meters mentioned above. The smart meter is provided by the grid operator for a fee of €20 to €50 per year.
Buy or rent a PV meter?
The measuring devices are usually rented from the network operator. They are housed in the meter cabinet and are therefore the responsibility of the network operator. The operator is responsible for installation, repair, replacement and maintenance. PV system operators can also buy the necessary meters themselves, but must ensure that they are calibrated regularly. This means that they must calibrate electromechanical meters every 16 years and electronic meters every eight years. They are responsible for the functionality of the meters. However, this option does not make sense for most operators and is rarely used.
Are counters that run backwards allowed?
Electricity meters are not allowed to run backwards in Germany. It is actually considered a criminal offence and usually results in a fine of up to €1,000. Theoretically, a prison sentence of two to five years is even possible.
You don't have to worry, though, because to commission a PV system you have to register it with the grid operator. The operator is responsible for the grid connection and also tells you whether you need a bidirectional meter or a smart meter. The risk of electricity meters running backwards only exists with balcony power plants.
