Slash energy costs by 30%

Ecobee Smart Thermostat ($385, Ecobee.com) / Honeywell RTH 7600d ($84, Amazon.com)

What it does: Lets you plug in times of day - such as when you leave for work or go to bed - to automatically raise or lower the temperature a set amount. The newest ones do some nifty things: The Honeywell offers settings for every day of the week, plus a vacation override; it even reminds you when to change your AC and furnace filters. The more expensive Ecobee (right) offers similar features and also allows remote programming over the web. So if you're stuck at work late, you can change the settings from the office.

Payback time: Set the temp 8° higher (lower in winter) for eight hours daily, and the Honeywell will realize savings in six months, the Ecobee in 26, as calculated from Energy Star data.

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