Officials say the extra hour of daylight this evening won’t mean big energy savings in Illinois.

ComEd expects only a small reduction in electricity use from customers waiting to switch on the lights.

Spokesman Luis Diaz says daylight-saving time isn’t usually one of the main factors affecting electricity use.

Diaz: The principal drivers on the ComEd system are weather. Hot weather’s going to put more air conditioners in use and that’s what really drives demand up. What daylight-savings time does is it reduces the demand for illumination, but it’s the major appliances in the households that are big drivers.

Congress decided in 2005 to move daylight-saving time from the first Sunday of April to the second Sunday of March. The change was intended to help save energy.