How to Install a Programmable Thermostat

By: Lance Marques, HVAC contractor, Swezey Fuel Co., This Old House magazine

a programmable thermostat with a hand-held remote

Photo: Ryan Benyi

4: Mount the Outdoor Sensor

About 1 hour
About $475 for the thermostat shown

Difficulty: Easy But if additional wires are needed, hire a contractor.

Q: I'd like to put in a new programmable thermostat to better control my energy costs. Can I install it myself?
—Sam Aleksy, Chicago

Lance Marques, HVAC contractor, Swezey Fuel Co., replies: Sure you can. Upgrading to a thermostat that automatically changes the indoor temperature setting is fairly easy, and it can trim about $180 off your annual heating and cooling costs, according to the EPA.

Simple models that only control heat are sold at home centers for around $25. More expensive products, such as the Honeywell Prestige that I installed here, handle many more functions, including cooling and humidifying. Typically they're purchased through and installed by HVAC contractors, but you can also buy them online.

Before you buy a replacement thermostat, however, take a peek at your existing wiring. If there are only two wires, the simplest solution is to get a replacement with a battery-powered display. Full-featured devices like the Prestige need power from a third wire, something best installed by an HVAC or electrical contractor.