Hydropower is one of the oldest forms of energy used and is most often produced in hydropower plants (HPPs). In them, the water flow falls on the turbines, turns them and generates electricity during the rotation process. In 2019, about 16% of all electricity consumed in the world was generated using hydropower. In 2020, in Latvia, approximately 44% of the total amount of electricity was generated using hydropower.

There are three types of HPPs:

• with water storage reservoirs,
• river run-offs,
• pumping plants.

HPPs with a water storage reservoir are most often built. Then it is possible to use the stored water at a time when there is a high demand for electricity or when there is a supply disruption from other countries. The water storage reservoir reduces dependence on the hydrological regime of the river, which can change due to different weather conditions. The volume of river water flow is particularly badly affected by extreme heat, significantly reducing the amount of water in it. Most electricity can be generated from HPPs in the spring months, when snow melts and water supplies in rivers increase.

Although HPPs are one of the most advanced renewable energy technologies, it is still possible to increase the amount of electricity generated in them without increasing the size of the water storage reservoir. The efficiency of HPPs can be improved by using more modern turbines, thus increasing the water flow force falling on the turbines, as well as by digitising HPPs.

Latvenergo AS generates most of its electricity from three Daugava HPPs – Pļaviņas, Ķegums and Rīga, the total installed capacity of which was 1,558 MW in 2020.