The district heating system with its constituent components that was leased in 2000 by Akmene’s energija for modernisation and optimisation, counted from 30 to 40 years of operation and demonstrated extremely poor operation results such as the inefficiency of energy generation and huge technical losses in the system. The variety of fuel used, such as environmental polluting coal and crude oil were still used and did not correspond to the modern perception of efficient and sustainable energy production. The result of the investments into modernization of probably the oldest district heating network in Lithuania certify a number of key indicators, among which the decreased heat transmission losses from 45% in the beginning of modernization in 2000 down to 8,8 % this year, as well as savings of fuel and electricity in the production process.