Most of the small-scale power plants connected to Caruna's distribution network use solar panels to capture energy from the sun. Most solar power plants are connected alongside houses or agricultural buildings that have several solar panels installed on their roofs.
A solar power plant consists of multiple solar panels with the total panel power designed to be close to the nominal power of the inverter, which determines the maximum possible output.
For example, the total panel power may be 13.24 kW and the inverter power is 12 kW, so the maximum possible output power is 12 kW.
Solar panels can cover the electricity consumed by a property
The electricity generated by solar panels can cover some or all of the property's electricity consumption. Solar power can also be used to charge electric cars.
In terms of profitability, it is essential that the solar panels provide the correct output and, insofar as is possible, that the solar panels generate electricity when you need to consume it.
In Southern Finland, a solar power plant of the right size can generate as much electrical energy as a plant installed in Northern Germany. Even when solar plants are installed further north in Finland, they are not far from these figures. In the darkest months of the year, solar panels only generate electricity for a short time, although the panels have a higher efficiency rate in colder weather.
Solar panels require very little maintenance, and they usually increase the value of a property. The break-even period for modern solar power plants is from 10 to 15 years, depending on the customer's own consumption and the scale of the solar panels.
Use the Caruna load control service to make the most of your solar panels
Electrical load control turns the heating and water boilers in the home on and off via the electricity meter. Customers often benefit from this service if they buy market-priced exchange electricity, but it is also a great way for solar panel owners to concentrate their electricity consumption in the daytime.
It makes sense to use water boilers and other heating or cooling using air-source heat pumps when the solar panels are generating electricity at the sunniest times of the day. The service can also be used to charge electric cars according to a schedule. The Caruna+ mobile app enables you to change the load control times to suit your needs.
Small-scale generation with other forms of generation
If you plan to generate electricity yourself using equipment other than solar panels, contact our customer service team to check the technical implementation of your power system. First of all, contact the supplier of the power plant or your electrical contractor to find out the following information:
The form of generation and the method for connecting to the network, e.g., a power plant with an inverter connection
The maximum output power
The technical realisation of protection, e.g., the applicable standard
The location of the power plant
You can provide these details to our customer service team using the chat feature.
Technical implementation of small-scale generation
Power plants, such as solar panels, are often connected to the main distribution board via a network device (also known as an inverter). Generator-type power plants, such as biogas plants, can be connected directly to the main distribution board via the generator.
The inverter changes the direct current that is generated to alternating current, and it also comes with protective devices and a user interface that enables the customer to monitor the volume of electricity generated.
The nominal output of a small-scale power plant is determined according to the plant's technical details. For example, the output power of a solar power plant is determined according to the nominal output of the inverter, such as 8 kW. The units may also kVA (kilovolt-amperes), which are equal to kilowatts in this case (8 kW = 8 kVA).
There is a disconnecting switch between the distribution board and the inverter so that the power plant can be safely disconnected from the electricity network. The disconnecting switch is usually installed on the exterior wall of the building or otherwise in a place that can be readily accessed by Caruna's technicians.
If there is a battery (or electricity storage system), it may be installed between the inverter and the main distribution board. A battery enables the generated electrical energy to be used at a suitable moment, and it also enables the generating plant to continue operating in the event of a fault in the electricity distribution network. The installation technician should be aware of the correct way of operating the generating equipment as a reserve power plant. For further details, see our contractor instructions <text link to the contractor instructions/reserve power>.
The generated and consumed electrical energy is metered at the accounting point's main distribution board or sub-meter reading centre (for example, if there is more than one electricity meter on the property). This ensures that the generated electricity is distributed for the property's use and/or any surplus electricity is transferred to Caruna's distribution network, and the electricity supplier compensates the customer for the metered number of kilowatt-hours fed into the grid.
Technical requirements for small-scale generating equipment
Small-scale generating equipment must comply with the SFS-EN 50549-1 standard. VDE-AR-N 4105 2018:11 is also approved for the time being, but no new equipment complying with this standard may be connected to the network after 2022.
All generating equipment rated at over 0.8 kW must comply with Fingrid's Grid Code Specifications for Power Generating Facilities (VJV2018).
Most ordinary solar power plants used by households and agricultural sites are micro-generation plants. It is usually possible to connect them within the limits of the accounting point's existing fuse size without making any changes to the distribution network.
The customer is not charged for any surplus electricity generated, and no taxes are levied on the generating equipment, irrespective of whether the small-scale producer consumes the electricity themselves or sells it to the market.
The generating equipment is also covered by netting, enabling an energy community to be set up. We provide more information about energy communities in a separate section.
Small-scale generation – output power from 100 kW to 2 MW
A larger output power may be of interest on service, commercial and industrial sites and on larger agricultural properties. If you are planning to install generating equipment with a power rating of over 100 kW, contact our customer service team using the chat feature at the start of the project so that we can clarify the requirements for connecting the generating equipment to the electricity network.
Generating equipment rated at over 50 kW is required to have a separate, centralised protection system, and it must not use ROCOF protection, which reacts to the rate of change in the frequency. Centralised protection may be relevant if you are using several inverters.
We charge for the energy fed into the grid in accordance with our electricity generation network service and connection fee price list.
The electricity generator must register with the Tax Administration as an entity liable for tax. If the output is over 100 kW, it is not possible to net the metered electrical energy or set up an energy community.
Netting of small-scale generation – output power up to 100 kW
When generating equipment is connected to an existing accounting point, the consumption and generation can be metered via the same electricity meter. The metering period is one hour, during which the electrical energy generated and consumed by the customer is netted, or calculated together for the same hour. Netting is used for generating equipment rated at up to 100 kW. In such cases, Caruna does not collect a fee for the distribution of the production to the distribution network, but a small producer needs to have an agreement for the sales of any surplus production.
Any unused surplus production transferred to the distribution network within one hour will reduce the small producer's distribution invoice by the corresponding amount.
If the customer generates more electricity than they consume in the same hour, the electricity supplier will compensate the customer for the surplus generation after netting.
If consumption is greater than generation in the same hour, the customer pays for the difference between consumption and generation for the hour in question.
All small-scale generators in Caruna's network areas are covered by automatic netting, and Caruna's electricity meters balance the small-scale generation and consumption of electricity momentarily between phases. Without netting, it would be possible to accrue both consumption and surplus generation in the same hour if these do not occur at the same moment in time. Netting improves the position of small-scale electricity generators, as Caruna nets small-scale generation and consumption on an hourly basis.
Example of the effect of netting on a small-scale generator
Caruna distributes a total of 2 kWh of electricity from the distribution network to a small-scale generator between midday and 1 pm.
In the same period, the small-scale generator's power plant generates a total of 7 kWh.
The small-scale generator consumes 4 kWh of this production, and 3 kWh is fed into Caruna's distribution network via the electricity meter in the home
Caruna deducts the 3 kWh surplus production, which has been distributed to the distribution network, from the 2 kWh of electricity distributed from the distribution network.
The small-scale generator pays nothing for the electricity distributed between midday and 1 pm from the distribution network. Instead, the small producer will be compensated by the electricity retailer for the remaining 1 kWh surplus production.
If there were no hourly netting, the customer would pay for 2 kWh of electricity distribution and receive 3 kWh of compensation for surplus generation from the electricity supplier in the same hour. It makes the most financial sense to consume the generated electricity on-site, and hourly netting makes this possible.
The customer's Caruna distribution invoice shows the amount of consumption to be invoiced after netting. The netted volume of electricity for the hour has, in other words, already been deducted from the amount of electricity distributed from Caruna's distribution network to the small-scale generator in the same hour.
The online Caruna+ service provides a wide range of metering data. You can see your billable consumption, as well as the volume of electricity generated. The service shows the amount of surplus electricity for which you will receive compensation from the electricity supplier. You can also see the net amount of electricity, which is directly deducted from your consumption and invoice thanks to netting.