A well-maintained furnace is a better means of keeping warm than cuddling with a camp stove or flooding the den with chicken soup. Raise the Fahrenheit with this Groupon.

$49 for an Air-Conditioner or Heater Tune-Up and Diagnostic Exam ($159 value)

After technicians arrive in a specially equipped service van, they awaken sputtering air conditioners and make whimpering heaters roar with a professional tune-up. The service includes a diagnostic exam to ensure optimum efficiency for year-round use.

J.H. Simpson Company

Established as a sheet-metal and furnace shop in 1944, J.H. Simpson Company has changed hands over the years but managed to keep up with the fickle winds of time by refocusing its efforts on reliable heating and air-conditioning services. J.H. Simpson Company's team of skilled designers, engineers, and technicians goes through the cramped corridors of ventilation shafts and into the bellies of furnaces to regulate household temperatures. When they aren't engaged in basic repairs, the team tackles new construction projects—from architectural sheet metal to stainless steel work—with the level of craftsmanship one might expect from dedicated Sheet Metal Workers Union members.