Hydropower
Hydropower is electricity generated from the kinetic energy of flowing water. In Finland hydro accounts for about 15–20 % of production and its great strength is fast controllability.
Hydropower's special quality compared to other renewables is controllability: turbines can be started and stopped rapidly and reservoir storage lets production be timed to expensive hours. In practice hydro rarely loses money on Nord Pool — it only runs when the price exceeds its cost level.
Finland's hydro plants are mostly in the north (Kemijoki, Iijoki, Oulujoki). Reservoir levels vary with the season and rainfall. After a dry year hydro can be scarce; after a wet year abundant.
Hydro's role is to balance wind variability: when the wind is low, hydro produces more, and vice versa. Together they form the largest share of Finland's renewable electricity.
Hydropower's special role in the power system
Hydro is the only renewable whose output can be adjusted rapidly to demand. The water behind the dam acts as a "battery" — the dam opens when electricity is needed and closes when not. Start-up and shutdown are a few minutes (vs nuclear: hours).
This makes hydro the power system's balancer. As wind varies, hydro fills in — on windy nights reservoirs refill (output saved), on calm days they are released. Together wind + hydro form a reliable renewable combination.
Finland's largest hydro operators
Northern Finland river plants — Kemijoki Oy (Kemijoki, parts of Oulujoki), Vattenfall (Ii, Oulu, Jolma) and Fortum (several river stretches).
Largest single stations: Vuolteenlampi (Kemijoki, 70 MW), Petäjäskoski (Kemijoki, 177 MW), Jylhämä (Oulujoki, 60 MW).
Finland's hydro capacity is about 3,200 MW. Annual production is 15–17 TWh — varying with rainfall (up to ±25 %).
Hydropower and the spot price
Hydro follows the spot price: output is adjusted to market price since storage allows timing. Hydro usually runs at full output during morning and evening peaks and reduced output at night.
Dry years (e.g. 2018) raise the spot price significantly — Finland's overall production drops, import need from Sweden rises. A wet year (e.g. 2024) lowers prices and Finland may occasionally export to Sweden or Estonia.
Frequently asked questions
Why is hydro important for the spot price?
Hydro output can be timed — on windy nights reservoirs fill, during more expensive evening hours they open. This balances wind variability and smooths spot price peaks.
How much hydro is produced in Finland?
Annual average 15–17 TWh, about 15–20 % of Finnish production. Dry years (e.g. 2018) up to 10 % less, wet years (2024) 20–25 % more.
Can more hydro be built in Finland?
The main rivers (Kemijoki, Iijoki, Oulujoki, Kymijoki) are already largely developed. Small uplifts are made via new turbines and dams, but no significant growth is foreseen — additional capacity will come primarily from wind and solar.
See also
- Wind power — Wind power is electricity generated by wind turbines. Finland's largest renewable source and a strong driver of the…
- Renewable energy — Renewable energy is electricity production based on continuous natural flows: wind, hydro, solar and biomass. In the Finnish…
- Nuclear power — Nuclear power is electricity from uranium fission. Finland has nuclear at Loviisa (2 units) and Olkiluoto (3 units)…