Frimley Park Hospital received a grant of £2.7m for the combined cooling, heat and power plant (CHP).
The plant has resulted in a carbon saving of 1,260 tonnes each year, the hospital claims, with surplus electricity sold to the National Grid.
A new surgery unit and increased theatre capacity had led to a higher demand for energy, said the NHS trust.
The combined heat and power plant, which was winched into place at the hospital in October 2008, has four blast coolers and two absorption chillers.
It provides a heat sink to run air conditioning systems in the summer and warms the main heating system in the winter.
The trust has a carbon management plan which sets out how it will reduce its carbon footprint by 15% by 2015.
The plan includes the replacement of 9,000 lights for energy-efficient lighting and upgrading the heating system in ward areas, saving about 90 tonnes of carbon dioxide per year.
Colin Mapperley, general manager of facilities, said: “The project has been a big success both in terms of the money it has saved and the lower impact on the environment. It really is a win-win.”