HORSENS DISTRICT HEATING SCALES UP GREEN HEAT SUPPLY WHILE TRIPLING ITS CUSTOMER BASE

Over a 10-year period, Fjernvarme Horsens (Horsens District Heating) has expanded from 8,200 to 22,400 customers and invested heavily in biomass, heat pumps, electric boilers, and surplus heat to maintain security of supply and support the municipality’s climate ambitions.

Original Danish text by Joel Goodstein, Danish District Heating Association, translated by DBDH | 17 March 2026

“The connection of new customers has taken place alongside the expansion of our production capacity, so it is very satisfying that we have now reached our goal – and in fact with more customers than originally planned,” says Christian Niederbockstruck, Managing Director of Fjernvarme Horsens.

In December 2025, Fjernvarme Horsens commissioned two new biomass boilers with a combined capacity of 30 MW, which proved their value already during their first winter in operation.

“Our new biomass boilers have already made a very valuable contribution during commissioning in a long, cold winter – and that is promising, even though the plant is still being phased in,” says Christian Niederbockstruck.

But the two biomass boilers are not stand-alone additions. They are, for now, the latest stage in a 10-year journey involving major investments in new heat production facilities at Fjernvarme Horsens.

“Since 2015, we have invested a total of DKK 2.3 billion in new plants and in connecting many thousands of new customers to district heating. Most of that investment, however, has gone into expanding the pipeline network. We now have a robust production mix and are well prepared to handle harsh winters, even though today we have more than 14,000 additional customers connected to the system compared to when we began the expansion,” he says.

From 2015 to 2025, the number of customers at Fjernvarme Horsens increased from 8,200 to 22,400 – a rise of 173%. In total, 470 km of new pipework has been established to serve the new customers.

The journey towards more customers and more sustainable heat production plants began with the approval of a project proposal to expand district heating in Horsens, also intended to support the municipality’s climate goals. At the time, the rollout benefited from mandatory connection requirements.

As more customers were connected, additional green heat capacity had to be established to phase out natural gas and reduce CO2 emissions.
Initially, 30 MW of biomass capacity was installed, but a range of other options for further expansion was later explored. These included wind power, surplus heat, geothermal energy, PtX, electric boilers, heat pumps, and carbon capture.

“We have turned over almost every stone to find the right sustainable solutions – even looking at a transmission pipeline that could transport surplus heat to Eastern Jutland from potential PtX plants near Esbjerg,” says Christian Niederbockstruck.

Future-proofing district heating

Originally, heat in Horsens was produced using natural gas and waste incineration. Today, heat is produced using waste incineration, four biomass boilers, surplus heat, heat pumps, and electric boilers – with a small amount of natural gas remaining for peak and emergency load.
Christian Niederbockstruck believes these billion-kroner investments have now future-proofed district heating in Horsens.

“Our forecasts indicate that we can reach 25,000 customers by 2030, including more commercial customers. But we expect to be able to supply the necessary amount of heat at least until 2040 with the plants now in operation,” he says.

Originally, the plan had been to introduce even more electrification of heat production rather than additional biomass.

“Before we installed the electric boiler and heat pump in 2021, we covered the cost of upgrading the underlying electricity grid, while our service connection had sufficient capacity. In 2022, we again entered into dialogue with our grid company about the possibility of connecting more electric-driven units to heat production. Already then, we found that the power grid – both DSO and TSO – in Horsens was undersized and underprioritised, and that grid capacity was fully booked,” says Christian Niederbockstruck. “For reasons of security of supply, we could not accept that, so we chose instead to expand with an additional 30 MW of biomass, which was a known and reliable solution with access to local biomass.”

He believes the current pause in the expansion of the Danish electricity supply system – with no clear timeline – will challenge the continued electrification of district heating across the country.

“In the current situation, phasing out biomass does not increase the sector’s security of supply. Instead, we need to introduce new technologies as they become ready. It may take 10 years before the power grid and electricity generation are sufficiently expanded, and until then we must use the technologies already available, including biomass, so that we do not compromise security of supply. Fortunately, we have other types of plants to produce heat until electricity capacity is expanded. That is our strategy in Horsens,” he says.

End of mandatory connection

There have also been other challenges and uncertainties along the way.

“Until 2019, we had mandatory connection requirements, which helped drive conversions, but it is important to remember that mandatory connection also comes with an obligation to supply. When the mandatory connection requirement ended, we became even busier. We chose a strategy where new customers receive a 50% discount on connection within the first year, and that has been a great success. In many areas, connection rates have been between 80% and 94%,” says Christian Niederbockstruck.

“All our customers were connected under mandatory connection requirements. Before these ended, we had all project areas approved with mandatory connection. That is why we were very busy connecting the remaining customers,” he adds.

The last customers in the project had the opportunity to connect in 2023. In some years, as many as 3,000 new customers were connected to the network. At times, more than 400 people were working on district heating installation.

“The connection of new customers has taken place alongside the expansion of our production capacity, so it is very satisfying that we have now reached our goal – and in fact with more customers than originally planned,” says Christian Niederbockstruck.