This spring, residents of seven western Massachusetts communities may see a hybrid SUV roaming the streets at night. There should be no cause for panic, though, because the people inside the SUV just want to use thermal imaging technology to measure and evaluate each home's energy performance. The initiative, which state officials are lauding as a national model for energy efficiency, is projected to save participants up to 20 percent on their electric and natural gas bills. The state's Department of Energy Resources is working with a Massachusetts-based contractor to identify spots where additional insulation and air sealing can prevent heat loss -- all from inside the SUV. Residents can then go online to see their home's thermal image, discover incentives, and find out their home's energy performance score, which takes energy use and carbon emissions into account. The program is funded by a U.S. Department of Education grant, which also financed similar efforts in Washington, Virginia and Alabama. Homeowners who would rather not have their homes subject to imaging can opt-out, and the contractor will delete photos as requested.