Solar power for your home

Frequently asked questions

Do you have any questions about solar power? See our frequently asked questions about microgeneration of solar power.

Solar panel on a roof 


In a solar power inspection, the most suitable solar photovoltaic system for the customer is designed and an offer on the installation work and equipment, including installation accessories, is made according to the specifications of the installation site.

You can deduct the share of installation work on your solar power package from the tax you pay. It is possible to receive tax credit for domestic costs up to the value of €2,400 in 2018. Our invoice includes itemisation of the share that is eligible for tax credit for domestic costs. You can make a tax deduction of 50 per cent of the installation costs from the total price of the solar photovoltaic system, and the excess is €100. Further information

Usually there is no need to apply for a separate action permit when the panels are installed parallel with the roof and the building is not marked for preservation. The operating models of different local authorities have not been harmonised yet, and therefore it is worth checking the matter with the building supervision authority of your own municipality before placing an order for a solar photovoltaic system.


In Southern Finland, the annual output of a solar photovoltaic system with a 1,100 Wp system at an angle of 30–45 degrees is about 900 kWh. Total annual output in the southern parts of Finland is about the same as in Northern Germany.

Annual amount of solar radiation (click to open the picture)

Wp stands for the peak output of the system in watts and kWp in kilowatts.

The solar panels come with an inverter, which is a device that converts the direct current produced by solar electricity into alternating current so that it can be used and fed into the electricity network. You can monitor on the device how much electricity has been produced. 

In the solar power inspection, we dimension the system according to your need. You will benefit the most from your solar photovoltaic system when all of the energy produced can be utilised in connection with the installation property, and therefore it is worth carrying out the dimensioning on the basis of normal property-related consumption. For example, during a holiday period, the consumption may be smaller than production and there will be enough surplus production to feed to the network. Therefore, it pays to draw up a sales contract with us with regard to surplus electricity.

Allocating electricity consumption is easier in a three-phase system than in a single-phase system. The three-phase system operates in the same way as network electricity and there is no need for changes related to the load allocation that may be necessary in a single-phase system. In a single-phase system, you have to choose the phase of the electrical centre where the system production is allocated to.


In order to operate, a photovoltaic cell does not need direct sunshine as it also develops electricity on a cloudy day. No solar energy is produced at night, and that is when the required electricity is taken from the electricity network. The biggest benefit and savings will be gained when you only consume electricity when the solar panels are producing it.

It is always worth positioning solar electricity panels so that they will not be in shade. Trees and structures that overshadow the panels will diminish the production of the system. It is more useful to rather build a smaller solar photovoltaic system than one with a larger nominal production which, however, will be partially in shade.

In practice, solar panels are maintenance-free and it is not necessary to clean them in any special way. Pollen washes away along with rainwater.

If the production of a solar photovoltaic system is higher than the property consumes, the surplus production will be fed back into the network. For the surplus electricity, Helen will pay an hourly price in accordance with the Finland price area on the Nordic electricity exchange (Nord Pool Spot). Draw up a sales contract by sending us an email to


The systems we offer are 230 V systems connected to the network, and their surplus electricity is not stored in accumulators, but fed to the network. Therefore, it is necessary to have an electricity connection at the installation site.

Unfortunately, a solar photovoltaic system connected to the network is not suitable to be used as reserve power because in an electricity network fault situation the solar photovoltaic system is automatically switched off in order to ensure the safety of the workmen repairing the system.