All about the solar energy calculation

The reduction in electricity costs is one of the primary motivations for investing in a solar power plant. Find out more about how solar energy is calculated.


The power of your solar power plant depends on the consumption of electricity and the technical capabilities of the facility (type of electrical connection, size of the facility, the material of the roof…).

Models for the calculation of electricity

In Croatia, there are two types of models for calculating electricity from solar power plants: a user of a solar power plant for household self-supply and a user with their products for other categories of customers (for example, companies that use renewable energy for production purposes).

The user of the solar power plant is connected to the power grid. Furthermore, the electricity that the user did not use is sold to the grid. If the user consumes more electricity than he delivers to the supplier (HEP), based on the calculation of the electricity of solar power plants, the user pays the difference between the used and delivered energy at the previously agreed tariff.

On the other hand, if the user’s solar power plant produces more electricity than the user needs, the unused electricity is sold to the power grid. Therefore, the excess electricity reduces the electricity bill.

The owner of a solar power plant can choose between single-tariff or two-tariff calculations of the electricity from solar power plants.

With the single-tariff calculation of the electricity from solar power plants, the user always pays for electricity according to the same daily tariff, while with the two-tariff calculation, there is a higher and lower electricity tariff (for example, the night is the period of the lower tariff).

SEMS, the GoodWe platform for monitoring the production of a solar power plant, also enables the display of available energy so that the user can adjust his consumption.

Electricity suppliers and solar energy calculation

The contract on the supply of the end customer with its production, allows the electricity suppliers to buy the excess electricity of solar power plant owners.

Under the conditions that the solar power plant owner:

  • has the status of a privileged producer of electricity
  • has the right to permanent connection to the electric power network
  • the total connection power of all production facilities in one metering point does not exceed 500 kW
  • connection power of the solar power plant’s production, is not greater than the connection power of the
  • owner’s connection power as a producer, is not greater than the owner’s connection power as a customer (of the electricity from the electricity supplier)

The solar calculator based on parameters such as the location of the facility, annual electricity consumption, and the type of power connection calculates the approximate power of the solar power plant needed to produce the average electricity needs and the minimum rooftop area needed to install the desired solar power plant.

One of the benefits is the calculation of the time in which you will return your investment.

Which electricity tariff you choose depends on the amount of consumption and the period when you consume the most electricity.
*each supplier contracts its terms and billing rates.

It takes a couple of minutes for you to calculate the expense of your solar project. Try it out here.