The Royal Alexandra and Albert School in Gatton Park is to spend #163;670,000 to make its heating and lighting more eco-friendly.
Surrey County Council has agreed to lend the money to the 150-pupil state boarding and day school to pay for green schemes.
The heating system in the school is on the same system as the residential areas - meaning that during the winter the school is heated at the weekends and overnight. By separating them, the school hopes to save #163;109,000 a year. New lighting will save a further #163;50,000 a year.
Peter Martin, the council's member for children and learning, said: "Our aim is for Surrey to have the lowest carbon emissions of any council in the country." hw.