The power reserve as insurance for the electricity system 

The power reserve is a resource that Svenska kraftnät has at the ready in the event of any electricity shortage in Sweden. During the winter, Karlshamnsverket is part of Svenska kraftnät’s power reserve. The power plant can also deliver other supporting services to ensure a secure electricity supply. 

Hydropower, nuclear power and wind power normally meet Sweden’s electricity needs. But when normal production is interrupted, or when the need for electricity is unusually high, Karlshamnsverket can be started up at short notice to deliver electricity. It only takes two hours for Karlshamnsverket to go from standby to production. 

Karlshamnsverket is fueled by oil and has a total capacity of 662 MW. It’s been a reserve power plant since the beginning of the 1980s. This is a task that we take very seriously and that we have done quite well at. You could say that the power plant functions as insurance for the entire electricity system. 

Karlshamnsverket – a reserve power plant in a constant state of readiness

This is how Karlshamns power station works

Listen to Henrik Pagels, operations manager at Karlshamns power station, when he shows us how Karlshamns power station works


The power reserve is the life line of the Swedish electricity system

Over a longer period, for example an entire year, Swedish has a surplus of energy and we export large amounts of fossil-free electricity to other countries. However, this doesn’t meant that there is enough electricity at any given moment. Karlshamnsverket is there for those moments – when the system suddenly needs extra capacity. This is mostly during the winter, when we use a lot of electricity in Sweden. That is why Svenska kraftnät has been tasked with managing the power reserve from November 16 to March 15 every winter. Karlshamnsverket is the production portion of the power reserve, contributing 562 MW. As the system operator, Svenska kraftnät has extended the power reserve agreement until 2025. 

The power plant is always staffed, regardless of the season or time of day, since interruptions to our electricity system can occur at any time. In addition to the power reserve, the power station can deliver several other supporting services, such as helping maintain a stable frequency in the electricity grid. The need for these services varies during the year – they’re not limited to the winter months. 

It’s essential for a reserve power plant to be able to start up quickly when needed. That is why maintenance and improvement projects are so important at Karlshamnsverket, and what we spend the most of our time on when we’re not in operation. Many employees have expertise both in maintenance and in operations. Operational staff work with preventative maintenance, and we start up our maintenance technicians jump in as reserve power technicians and operate the power plant together with their operational colleagues. 

Read more about how procurement with Svenska kraftnät works.

With the environment in focus 

The environment is very important to us. When you see smoke coming out of our chimneys or a large oil tanker in our port, remember that we work deliberately and systematically with all kinds of environmental issues that are relevant for our operations. We are ISO 14001 certified, which is an international standard that establishes what a company needs to do to have a structured environmental agenda. Certification means that we meet the high standards that certified companies adhere to in terms of environmental expertise and procedures. If you have questions about our environmental policy or goals, you are welcome to contact us at  [email protected]

In the 1990s, we made major investments to reduce the power plant’s emissions. We installed an NO₂ catalytic converter in blocks 2 and 3. In block 3, there is also an electric filter and a desulfurization facility, with a proprietary technology and removal rate of more than 98%. That also makes it possible to use higher sulfur oil in block 3, and still keep emissions well below the given maximum levels. 

Burning oil also creates carbon dioxide. Karlshamnsverket is part of the EU’s Emissions Trading System, which is an important tool for reducing carbon dioxide emissions. 

Effective flue gas cleaning in three steps 

Effective flue gas cleaning in three steps

Step 1

Nitrogen oxides are removed from the flue gas in a catalytic converter 
Flue gases pass through the catalytic converter after being injected with vaporized ammonia through narrow ceramic channels. The ceramics are doped with vanadium pentoxide, which is the active component in the catalytic reaction. The subsequent chemical reaction creates water and nitrogen gas, which are both natural components in the air we breathe. The catalytic converter removes over 85% of the nitrogen oxide. 

Step 2

Dust and soot is removed from the flue gas using an electric filter 
In the electric filter, flue gases pass through an electrically charged field where dust particles are trapped in large sheets. The removal rate is over 90%. The dust is sent to reprocessing, where its valuable contents of the metals vanadium and nickel are collected. 

Step 3 

In the desulfurization facility, sulfur is removed from the flue gas to become usable gypsum 
The desulfurization technology used is based on an idea developed at the power plant. The desulfurization facility has a removal rate of over 98%. 

The first step in the desulfurization facility is a scrubber. Here, any particles that passed through the electric filter are removed and the flue gases cooled and injected with liquid. This high level of dust removal means that the flue gases are almost entirely free from dust and heavy metals when they go to the absorber for desulfurization. This guarantees that the final product from the facility, gypsum, is extremely clean. 
In the absorber, sulfur dioxide in the flue gases reacts with finely ground limestone to produce gypsum. The gypsum produced in the absorber is removed using hydrocyclones and vacuum band filters. Gypsum is primarily used as raw material in gypsum boards.

This is how flue gas cleaning works at Karlshamns power station

Listen to Henrik Pagels, operations manager at Karlshamns power station, when he shows us how flue gas cleaning at Karlshamn power station works.

The latest news about Karlshamnsverket (Swedish)

All our power plants in Sweden


OKG is a nuclear power plant situated in the Simpevarps Peninsula, Oskarshamn, Sweden.

Hydro powerplants in Sweden

Uniper engineer inspecting a hydro plant in Sweden
Our hydro power assets in Sweden includes 76 run-of-river plants, located from Lycksele in the North to Kristianstad in the South.


Karlshamnsverket is an oil-fired peak and reserve power plant. It’s situated in southern Sweden, which requires more capacity than other parts of the country. Karlshamnsverket is the production portion of the power reserve, which is procured by Svenska kraftnät for the winter period.


Barsebäck is a decommissioned nuclear power plant situated in Barsebäck, Skåne, Sweden.

Find out more

Karlshamnsverket is the largest peak and reserve power plant in Scandinavia. The facility is final life line of the Swedish electricity system.  

We work deliberately and systematically with all kinds of environmental issues that are relevant for our operations.

The laboratory at Karlshamnsverket conducts analyses for Uniper as well as external customers.

Our global presence

We continue to strengthen our presence in key markets, develop innovative solutions and acquire companies in prioritized areas. Uniper solutions are sold to over 100 countries and we currently operate in over 40 countries.