Carrier and IBM are testing an Internet-based ac control service this summer in Europe that would let consumers start cooling their homes before leaving work and could help utilities conserve power.

Homeowners would be able to use a Web site, www.myappliance.com, to control the operating temperatures of their Carrier brand air conditioners from work or elsewhere. They could set back on the cooling when they leave for work in the morning, then change it again before they leave work for home. Dealers, installers, and engineers could diagnose mechanical trouble without home visits.

A pilot program will be launched this summer in Britain, Greece and Italy.