The district heating power plant Neudorf-Werndorf was erected by Steirische Wasserkraft- und Elektrizitäts-AG (STEWEAG). The planning for this power plant was part of a concept which provided for the construction of four power plants on the Mur between Lebring and Spielfeld as well as an oil-fired steam power plant. The realisation of the concept commenced in 1962 with Gralla power plant. In 1966, a decision was taken to erect the steam power plant Neudorf-Werndorf. With a capacity of 120,000 kW, this power plant would cover the winter supply gap of the run-of-river power plants on the Mur and Enns.
Due to the cooling water requirements, the selected location lay on the Mur south of the consumption center Graz, namely in the municipalities Neudorf and Werndorf. Decisive factors in the determination of the exact location were the 175-meter high stack - due to air traffic - as well as the possibility of establishing a rail connection. The planned construction of a refinery 15 km from the power plant location was also considered as this would greatly reduce transport costs for the heating oil. From the beginning, the power plant was designed to accommodate two machine units. As the selected site is a flood drainage area, the power plant was constructed approximately 80 m from the bank of the Mur, the ground level was raised by approximately two meters and a flood-proof dam was erected around the oil tanks.
The construction decision for the first block "Neudorf-Werndorf 1" was issued on 17 September 1966. The construction contracts for the machine units and the boiler had been awarded prior to this. Ferdinand Schuster, who claimed to be an "expert in matters relating to form" and was also a member of the planning team right from the start, was commissioned to handle the architectural design. When constructing the buildings for Block 1, the architect Ferdinand Schuster included the planned expansions of later years in his concept and positioned the boiler house, machine hall, outdoor switching station and oil tanks in such a way that each of these elements could be extended in at least one direction. This approach was, however, not pursued consequently. The stairwell tower of the boiler house for Block 1 proved to be a hindrance during the construction of Block 2 and therefore had to be removed. The structural steelwork, including the boiler, was completed by Waagner-Biró. The construction work included the implementation of technical innovations in Austrian thermal power plant construction, such as the braced steel stack, the sprung foundation for the turbine and the lightweight construction of the machine hall. The main works were completed in 1967 and 1968. The assembly of the framework for the boiler commenced in spring 1967 and the first part of the turbine, namely the condenser, was mounted in autumn of the same year. The first heating oil was delivered in April 1968 and the preparatory work prior to commissioning was carried out from May to September 1968. The power plant was finally commission in October 1968. The power plant had a capacity of 120,000 kW and was powered with heavy heating oil. At the beginning of plant operation, trucks were used to transport the oil at the rate of one truck per hour. A two-story steel building was constructed by Waagner-Biró for the construction workers. On completion of the construction work, this building was signed over to STEWEAG and was subsequently used as an administrative building.
In the years 1972 to 1975, the second block "Neudorf-Werndorf 2" was added and, in the course of the construction work, the air preheaters and blowers for Block 1 were also housed in 1976. Prior to the commissioning of Block 2, Neudorf-Werndorf 1 was operated as a base load power plant. In July 1976, a new railway station was erected thus facilitating the delivery of oil by rail. For noise protection reasons, the open aggregates and air ducts that were built onto the boiler house were enclosed in 1976. In 1978, Neudorf-Werndorf 1 received a gas connection. In 1981, Steirische Wasserkraft- und Elektrizitäts-AG (STEWEAG) was awarded the Geramb Rose for the design of the stack, which had been planned by Waagner-Biró in cooperation with Ferdinand Schuster. The boiler in Block 1 was renewed between 1982 and 1985. Following the commissioning of the district heating power plant Mellach in 1986, Neudorf-Werndorf 1 was used to cover peak demand periods and also served as a failure reserve for Mellach. In 1989, Neudorf-Werndorf 1 was converted to facilitate low-emission firing with natural gas in low-nitrogen boilers. In addition, extra light heating oil could be used as an emergency fuel. This led to a reduction in capacity from 120,000 kW to 110,000 kW. In 1992, the condensing turbine was converted into an extraction condensing turbine and the required components for district heating decoupling were installed. This resulted in a maximum heating capacity of approximately 180,000 kW and a maximum electrical capacity of around 70,000 kW. The office space added to the machine hall was planned by the STEWEAG architect Petric, who was also responsible for the enclosure of the heat exchanger on the east side of the machine hall. The power plant was taken off line in 2004.
Following the construction decision on 16 November 1971, the block "Neudorf-Werndorf 2" with a capacity 175,000 kW was erected between 1972 and 1975. Together with Block 1, the power plant generated 295,000 kW and, at the time it was built, would have been able to cover approximately half of the electricity requirements in Styria. The architectural design of Neudorf-Werndorf 2 originated from Ferdinand Schuster, the architect who had already planned Neudorf-Werndorf I. The buildings were completed according to his plans after his death in 1972.
With a view to taking advantage of the low groundwater levels, excavation and foundation work commenced in November 1972. The first foundation concrete was laid in mid-December on completion of the soil compaction measures. The stairwell tower of Block 1, which was located on the north side of the boiler house and therefore within the area planned for the new Block 2 buildings, had to be completely removed.
The underground construction of the machine hall, including the concrete work for turbine decks, was completed by the end of August 1973. The entire machine hall including housing and roofing was completed by December 1973. The assembly of the boiler commenced in September 1973. The steel structure for the boiler house was completed in December 1973 and work on the assembly of the boiler was continued in 1974 and 1975. Full steam capacity was achieved for the first time on 27 September 1975.
Two heating oil tanks, each weighing 50,000 tons, were erected within the framework of the construction work thus increasing the storage capacity to a total of 200,000 tons. This amount more or less corresponds to the annual requirement of the power plant. The excavation and soil compaction work for the oil trough was completed in spring 1974 and the steel construction for both oil tanks commenced at the beginning of July in the same year and was finally completed in February 1975. The excavation work for a second pump house for cooling water also commenced in March 1974, the workshops were extended, chlorination facilities and a second storage building were erected, the outdoor switching station was expanded and the oil pump house was modified. The residential area for the workers was extended through the addition of a six-flat apartment building. Most of the work was completed by 1975. The construction of a gas reduction facility and a connecting railway line for oil filling commenced in July 1975 and was completed by mid-1976. The power plant's own natural gas connection to the network of Steirische Ferngas-Ges.m.b.H. exists since 1975 and, from 1976 onward, it was also possible to operate Block 2 with natural gas.
During the construction of the district heating power plant Mellach from 1983 to 1986, one of the two oil tanks in tank yard 2 was converted to an ash silo which is now used to carry the ash produced in the district heating power plant Mellach over the Mur via a bridge. As the emission values for Block 2 lay above the limits specified in the Clean Air Act, it was decommissioned in 1989 and extensive work was carried out in the following years to reduce pollutant emissions. The first Eco Audit in accordance with ISO 14001 was carried out in March 1995. In 1996, the buildings for the flue gas cleaning system and the wet electrostatic precipitator buildings were erected in accordance with the design of the architectural firm Gamerith-Kampits. The same architects were responsible for the adaptation measures for Block 2. Following the integration of flue gas and waste water purification facilities as well as a combined heat and power generation system, "Neudorf-Werndorf 2" was commissioned in 1997 after being out of operation for eight years and has been supplying district heating ever since. The office space added to the machine hall was planned by the STEWEAG architect Petric, who was also responsible for the enclosure of the heat exchanger on the east side of the machine hall. The costs of the adaptation measures came to approximately 1.1 billion Austrian Schillings. In 2005, a 25,000-liter oil tank, which originally contained extra light heating oil, was rented out and filled with bio diesel. The extra light heating oil was sold.