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Thermostats Without Mercury

Most thermostats sold today don’t contain mercury. Programmable electronic thermostats and many manual thermostats are now mercury-free. Honeywell makes a round thermostat that doesn’t contain a mercury switch that looks exactly like the older mercury-containing thermostat.

How to find out if a thermostat contains mercury

Two types of thermostats typically do not contain mercury switches:

  • Electronic thermostats with a digital display: these are programmed to go on and off using a key pad;
  • Thermostats controlling electric baseboard heaters (the metal heaters that run along the bottom of a wall, controlled by a knob or dial).

For new thermostats, check on the package. Thermostats with mercury will have the “Hg” sign for mercury on the packaging.

For thermostats in use, take off the cover and look inside. If there is a glass ampoule (or ampoules) containing a silvery substance, the thermostat contains mercury.

Are thermostats without mercury reliable?

Mercury-free thermostats are just as reliable and easy-to-use as those that contain mercury—and they conserve energy. These thermostats are widely available.


Check energy utilities like Seattle City Light or Puget Sound Energy to see if rebates are available for the purchase of programmable thermostats.

For more information contact Taylor Watson, Health and Environmental Investigator, at