Connecting generating equipment and battery storage systems to the electricity network

Information on all equipment connected to Caruna's network that can supply electricity to the electricity network must be provided on the general request form. In addition to solar panels, these include battery storage systems, bidirectional car charging points, batteries and small-scale wind power stations.

Your electricity contractor fills in the general request form on Caruna's website.

Even if your generating equipment or battery storage system is scaled to utilise most of the production in your own consumption, the electrical energy you generate may exceed your own consumption momentarily. In this case, the surplus or stored electricity is transferred to Caruna's network. This is common for solar plants, which have the highest output in the summer when consumption is usually lower than in the seasons in which buildings are heated.

Small-scale generators must have a buyer for the electricity they produce. Even if there is no surplus output, you need to make an agreement in accordance with the general terms of network service. This also applies in the event that an electricity supplier's agreement ends due to a move or change of supplier. In these cases, a new agreement must be made with the selected electricity supplier for the generation and consumption point.

If a power plant has a nominal output of up to 100 kW, no electricity tax is paid on the generated electricity, and Caruna does not collect a fee for the surplus electricity fed into the network. Most ordinary solar power plants used by households and agricultural sites have nominal outputs within this range.

If the output power exceeds 100 kW, we charge for the surplus electricity fed into the network in accordance with the electricity generation network service and connection fee price list.

You can monitor your electricity consumption and the volume of surplus electricity generated in Caruna+ once you have received a connection permit for the generating equipment.

You can monitor the total amount of electricity your solar panels generate by checking the screen on the inverter connected to your solar panels or by accessing your equipment supplier's service.

Caruna is responsible for measuring the volumes of consumed energy and energy fed into the network. The same electric meter is used for these purposes. We measure consumed and generated electricity as 15-minute average values. Netting of generation and consumption is carried out in the datahub service maintained by Fingrid.

Almost all Caruna electric meters can be remotely activated as bidirectional without changing the meter. Activation takes place when processing the production general request form from your electricity contractor. We will contact you if the meter must be changed. We deliver the metering data through datahub to your electricity supplier, which buys the surplus energy fed into Caruna's network.

All equipment under 100 kW is automatically covered by netting when a connection permit has been granted.

The recommended size of the generation plant depends on several factors, such as the volume of electricity you currently consume, your consumption profit (including how you heat your property and the effect of charging electric vehicles), location and your budget.

The factors specific to solar plants include your roof's surface area, direction and any shadows cast upon it. An expert supplier or electricity contractor can help you decide on the ideal size of your power plant.

The peak power of generating equipment is calculated according to its technical properties. For example, the nominal output power of a solar plant is determined based on the inverter data. The units of power may be kW (kilowatts) or kVA (kilovolt-amperes), which are equal to each other in this case.

The amount of compensation depends on your agreement and the services provided by your electricity supplier. You can find out about compensation by requesting quotes from different electricity suppliers.

Some municipalities may require a permit for measures such as installing solar panels. You should verify local requirements with your municipal building control authority.

Caruna will issue commissioning approval for the generation system by text message once:

• You have verified that the system can be connected to your electricity connection.
• Your electrical contractor has submitted the General Information Form.
• You have signed an agreement for the sale of surplus electricity with your electricity supplier.

If we are unable to grant connection approval directly, we will contact you.

It must be possible for a Caruna technician to disconnect your generating equipment from the electricity network if necessary, for example, to repair a fault. For this purpose, there must be a disconnection switch installed in an accessible location, such as the exterior wall of the building. If the disconnection switch is in a locked area, such as an engineering and utility services room, you must arrange access according to our guidelines.

Housing companies typically install a shared generation system connected to the property's common electricity meter.

Individual apartment-specific generation systems are also possible, for example if solar panels can be installed on the roof of a terraced or detached house and the housing company has granted permission. In semi-detached houses, it is advisable to agree on the installation with your neighbour. Separate generation systems may be installed for both dwellings.

When sizing generation systems for housing companies and semi-detached houses, the output of all systems connected behind the same electricity connection must be added together. Different generation technologies, such as solar and wind power, must also be aggregated because they are located behind the same physical connection.

The owner of the electricity connection can verify connectability in Caruna Plus.

If the power or technical implementation of the generating plant changes, your electricity contractor must notify us of the changes using the general request form. We will check the connectivity of the equipment based on the changed output power.

Example: A 15 kW battery storage system is installed alongside an existing 3 kW solar power system. Connectability will be assessed based on the combined maximum export capacity of 18 kW.

Software-based power limitations are accepted. In such cases, connectability is assessed based on the limited output.

You can build a power plant on property other than the consumption point of delivery connected to it (such as a house or industrial facility). The real estate may be owned by a different party, and the property does not need to be geographically adjacent. 

The landowner must grant permission to build the power plant, and you must get the necessary permits from the authorities and municipality. You are responsible for building a connection line between the generating plant and the switchboard at the consumption point of delivery.

No. For electrical safety reasons, power plants switch off automatically at the beginning of a power cut and back on after the power cut.

If your power plant is connected to a battery, you can use the electricity stored in the battery if there is a fault in the electricity network. Consult the equipment supplier or your electricity contractor to check the technical implementation.

A small-scale power plant is usually a profitable investment that raises the value of real estate. When you sell your real estate, it is a good idea to tell potential buyers about the power plant – for example, solar panels on the roof.

When you have sold the property, the new owner should transfer the electricity connection into their name and make an agreement with their chosen electricity supplier for the consumption and generation point of delivery. This will enable the buyer to take advantage of the electrical energy they generate.

Please notify our customer service when your generation system is being removed.

We will delete the equipment details from the point of delivery and end the agreement for the generating point of delivery. We will also notify your electricity supplier.

If the generating equipment is removed when the building is demolished, the change can be made when the electricity connection goes into maintenance or is terminated. The generating point of delivery agreement can end on the day when our technician removes the electricity meter. After that, we will delete the equipment details from the point of delivery.

If the maximum power fed to the network by the generating equipment is limited by a separate smart control system, connectivity can be considered on the basis of the limited output power. This can make sense, for example, for sites with more than one form of production. Without such limitations, the generation capacity must not exceed the maximum capacity allowed under the connection agreement and installed main fuses.

If the generation system exceeds the connection's permitted capacity, you should apply to upgrade the connection to a production connection.

Electricity generators fall into three categories in terms of their electricity tax liability:

Output power up to 100 kVA

Small-scale generators are not liable for electricity tax. Small-scale generators do not need to register as liable for tax, nor do they need to file tax returns on their electricity generation.

Output power over 100 kVA, up to 800,000 kWh of electrical energy generated per year

The electricity generator must register with the Tax Administration as an entity liable for electricity tax. The electricity generator must file an annual tax return so that the annual generation limit can be supervised.

Output power over 100 kVA, more than 800,000 kWh of electrical energy generated per year

The electricity generator must register with the Tax Administration as an entity liable for electricity tax. The electricity generator must file a monthly tax return, irrespective of whether the power plant feeds electrical energy into the network. No electricity tax is levied on the electricity used for the power plant's internal consumption.