Energy costs for Harvard's school buildings have plummeted by about 23 percent over the past four years, according to a report from the Harvard Energy Advisory Committee. The drop in energy consumption, with its corresponding savings in dollars and cents, resulted from a series of upgrades to equipment and control systems, Energy Advisory Committee Chairman Brian Smith told the School Committee in a report on Oct. 11.

The report showed that the schools' total energy bill in fiscal year 2008 was $414,036. For fiscal year 2011, that bill was down more than $90,000 to $320,823. Costs in the interim years were even a little lower, but a bump in energy prices and a slight increase in usage during last year's cold winter raised the 2011 total, Smith said.

Smith explained that the Bromfield School has shown the biggest improvement—a 40 percent drop in energy usage—because it is the biggest energy user among the school buildings. Bromfield accounts for about two-thirds of the energy usage, according to a pie chart in Smith's presentation. Hildreth Elementary School accounts for about one-third, and Bromfield House (the administration building) uses only a tiny sliver of the energy total.

While energy usage at the elementary school has changed little, costs have nonetheless dropped because of the conversion from oil to less expensive natural gas, Smith said.

Smith listed some of the changes that the schools have implemented since 2008 at his committee's recommendation, including new boilers and burners, upgrades to lighting, and improved control systems for heating and ventilation.

In looking for further energy savings, Smith said the Energy Advisory Committee hopes to do another school staff survey to find remaining problem areas. The committee also plans to review gas usage at the elementary school and electricity usage at Bromfield.

Smith noted that Bromfield's electric usage has increased in the past year. One possible cause is that some air handlers that were broken are now working again, providing better temperature control in the gym and the science wing, but at the expense of some electricity.