A programmable thermostat is nearly as effective at saving energy as a smart thermostat, according to tests conducted by Stelpro and the École Polytechnique de Montréal:

Mechanical (Bimetallic) Thermostat : Baseline energy usage

Electronic Thermostat : 12-16% yearly energy savings

Programmable Thermostat : 20-24% yearly energy savings

Smart Thermostat: 25-30% yearly energy savings

Nevertheless, 89% of people who own a programmable thermostat don't take the time to program it, according to research conducted by the American Council for an Energy Efficient Economy.

This laziness is expensive. "The average household spends more than $2,200 a year on energy bills, with nearly half of this going to heating and cooling costs," according to the U.S. Environmental Protection Agency. Meanwhile, a well-reviewed programmable thermostat sells for around 1% of that cost.

How Much Does a Smart Thermostat Cost?

A good smart thermostat (with verified, above-average reviews) costs approximately $126, according to a 12-month analysis of price trends. Those same WiFi thermostats cost around $92 while on sale: an average discount of 27%. Many utility companies also offer rebates on Energy Star certified smart thermostats.

For example, Con Edison offers up to $210 in rebates on Honeywell and Nest Thermostats. New Yorkers can effectively get a "free" smart thermostat and start saving on energy costs immediately.

Not every program is as generous as Con Edison's, but the Energy Star Rebate Finder publishes a list of local subsidies, rebates and discounts on thermostats and other energy-saving products.

Is a Smart Thermostat Worth It? Lowering (or shutting) the thermostat while away is one of the most effective ways to minimize electricity and natural gas consumption, according to a study published by the Institute of Electrical and Electronics Engineers. For example, Energy-Star certified smart thermostats save at least 8% in heating energy and 10% in cooling energy per year in 4 out of 5 American homes. Therefore, a $100 WiFi thermostat should pay for itself in around a year; a $200 learning thermostat should pay for itself in around two years.

This article is focused on Wi-Fi connected thermostats that allow temperature adjustments to be made on a smartphone or tablet, but the majority of these smart thermostats are not "learning thermostats."