Economizers don't heat or cool anything - they simply bring in cool, fresh, outdoor air to help cool a building naturally.  When outdoor conditions are favorable for cooling, the economizer brings in fresh cool outdoor air.  If the outdoor conditions aren't favorable, the system uses air conditioning. Using a Honeywell economizer with demand control ventilation can reduce your energy costs as much as 40 percent when installed and maintained properly, depending on geographic region and building usage.  Learn more about Honeywell economizers, including the JadeTM Economizer here.