By the end of the 1970s, Gothenburg system had grown to encompass eight large ‘district heating islands’ in Gothenburg. All power and heating plants were fed by oil-fired hot water stations. At this time, electricity prices were low and oil prices had reached record heights. The situation for district heating operations in Gothenburg was not economically sustainable. Goteborg Energi decided to make a change. The eight district heating islands were linked together, producing a connected network. The next major step was receiving large amounts of waste heat. Fuel efforts began in the early 2000s. Rya heating plantas hot water boiler was converted from natural gas to wood pellets in 2003. In addition to waste heat generated by electricity production in Gothenbiurg’s plants, waste heat is recycled from two large refineries and from the region’s waste incinerator at Renova. Waste heat recovery by Goteborg Energi’s district heating network produces great environmental benefits. Today, nearly 80% of the city district heating is based on waste heat.