In November 2007, Maryland enacted legislation creating a sales and use tax "holiday" for certain energy-efficient appliances, beginning in 2011. Under the law, qualifying appliances purchased during a designated period are not subject to the state sales and use tax (6%). The holiday time frame is established as a three-day period running from "the Saturday immediately preceding the third Monday in February through the third Monday in February each year". In 2015, the holiday runs from February 14 to February 16. 

In order to qualify for the exemption, qualifying pieces of equipment must be designated as meeting or exceeding the efficiency requirements of the ENERGY STAR program. The law defines eligible ENERGY STAR product types as follows:

• Air conditioners (ENERGY STAR designation includes both central and room air conditioners)
• Clothes washers*
• Furnaces
• Heat pumps
• Standard size refrigerators
• Compact fluorescent light bulbs
• LED lighting
• Dehumidifiers
• Boilers
• Programmable thermostats**

The law also lists solar water heaters and heat pumps (presumably including geothermal heat pumps) as eligible for the exemption. However, a separate law offers a less restrictive year-round sales and use tax exemption for renewable energy equipment, including both solar water heaters and geothermal heat pumps. Frequently asked questions about the incentive can be accessed here. 

*While the law also defines clothes dryers as an eligible appliance, the ENERGY STAR program does not currently certify clothes dryers.

**The ENERGY STAR specification for programmable thermostats was suspended December 31, 2009.