Earth Month Tip: Change your HVAC system filter
Check your filter every month, especially during heavy use months (winter and summer). If the filter looks dirty after a month, change it. At a minimum, change the filter every 3 months. A dirty filter will slow down air flow and make the system work harder to keep you warm or cool — wasting energy and contributing to climate change.
More tips: http://www.epa.gov/earthday/actonclimate/