Energy Rebate Glossary

The process of closing gaps and cracks in a home's exterior to prevent unwanted air leakage. Common areas include around windows, doors, electrical outlets, and where pipes enter walls.

A heat pump that transfers heat between your home and the outside air. Works for both heating and cooling. Modern cold-climate models work efficiently even in sub-zero temperatures.

The midpoint of a region's income distribution. Used to determine eligibility for income-qualified rebate programs. Different from State Median Income (SMI).

A diagnostic tool used during home energy assessments to measure air leakage. A powerful fan is mounted in an exterior doorway to depressurize the home and identify where air is escaping.

A unit of energy equal to the amount needed to raise one pound of water by one degree Fahrenheit. Used to measure heating and cooling capacity of HVAC equipment.

A measure of heat pump efficiency showing the ratio of heat output to electricity input. A COP of 3.0 means the system produces 3 units of heat for every 1 unit of electricity used.

A heat pump specifically designed to operate efficiently in temperatures as low as -15°F or below. Required for Mass Save rebates to ensure performance in Massachusetts winters.

A heating/cooling system that uses ductwork to distribute conditioned air throughout the home. Includes traditional furnaces and some heat pump configurations.

A type of heat pump with individual wall-mounted indoor units connected to an outdoor compressor. Doesn't require ductwork, making it ideal for older homes or room additions.

A measure of cooling efficiency calculated by dividing cooling output (BTUs) by power input (watts). Higher EER means better efficiency. Used alongside SEER for air conditioners and heat pumps.

See "Home Energy Assessment." A comprehensive evaluation of a home's energy use and efficiency, identifying opportunities for improvement.

Also called geothermal, these heat pumps use underground loops to exchange heat with the earth. More expensive to install but extremely efficient, with rebates up to $25,000.

A 0% interest loan program offered through Mass Save for energy efficiency improvements. Loans up to $25,000 with terms up to 7 years, available to customers of participating utilities.

An electric system that moves heat rather than generating it by burning fuel. Provides both heating and cooling. Types include air source, ground source, and heat pump water heaters.

A water heater that uses heat pump technology to heat water 2-3 times more efficiently than conventional electric water heaters. Eligible for rebates up to $1,250.

A free, comprehensive evaluation of your home's energy performance conducted by a certified Mass Save specialist. Identifies efficiency opportunities and determines rebate eligibility.

A measure of heat pump heating efficiency over an entire heating season. Higher HSPF means better efficiency. Minimum requirements apply for rebate eligibility.

The updated testing standard for heat pump heating efficiency, introduced in 2023. Mass Save rebates require minimum HSPF2 ratings (typically 7.8 or higher).

Programs offering enhanced rebates (often 2-3x standard amounts) for households meeting income guidelines. Typically at or below 60% or 80% of State Median Income.

Uncontrolled air leakage into a building through cracks, gaps, and holes. A major source of energy loss that air sealing addresses.

Material that slows heat transfer between inside and outside of a building. Measured in R-value. Common types include fiberglass, cellulose, and spray foam.

A unit of power equal to 1,000 watts. Used to measure electrical capacity. A typical home uses 10-15 kW of solar panels.

A unit of energy equal to using 1,000 watts for one hour. What you're billed for on your electric bill. Average Massachusetts home uses about 600 kWh per month.

An electric vehicle charger that uses a 240-volt outlet (like a dryer outlet). Charges 5-10 times faster than a standard outlet. Eligible for rebates up to $1,400.

Low Income Home Energy Assistance Program. Federal program that helps low-income households pay heating bills. Participation may qualify you for enhanced rebates.

Massachusetts' statewide energy efficiency program, sponsored by utilities and energy companies. Offers rebates, incentives, and 0% financing for energy upgrades.

A locally-owned and operated utility company. Massachusetts has 40+ municipal electric utilities. They don't participate in Mass Save but may offer their own programs.

Utility companies that fund and participate in Mass Save programs. Includes Eversource, National Grid, Cape Light Compact, Unitil, Berkshire Gas, and Liberty Utilities.

Required authorization from Mass Save before starting certain projects. Mandatory for rebates over $10,000. Ensures equipment meets efficiency requirements.

A measure of insulation's ability to resist heat flow. Higher R-values mean better insulation. Attic insulation in Massachusetts should be R-49 to R-60.

A partial refund after purchasing qualifying equipment or completing energy efficiency work. Can be instant (applied at purchase) or mail-in (check sent after application).

A contractor approved by Mass Save to perform rebate-eligible work. Using a registered contractor is required for most rebates. Find them on masssave.com.

The perimeter of a home's floor framing system, sitting on top of the foundation. A common area of heat loss that benefits from insulation and air sealing.

A measure of cooling efficiency over an entire cooling season. Higher SEER means better efficiency and lower operating costs.

The updated testing standard for cooling efficiency, introduced in 2023. Mass Save rebates require minimum SEER2 ratings (typically 15.2 or higher for heat pumps).

Solar Massachusetts Renewable Target. State program providing incentives for solar installations based on the electricity generated. Payments last 10 years.

The midpoint of Massachusetts household income. Used to determine eligibility for income-qualified programs. Different from Area Median Income (AMI).

Insulation that expands when applied, filling gaps and creating an air barrier. Available in open-cell (R-3.7 per inch) and closed-cell (R-6.5 per inch) varieties.

A dollar-for-dollar reduction in taxes owed. Federal tax credits for energy improvements (25C, 25D, 30D) can be combined with Mass Save rebates.

Heat transfer through building components (like studs) that conduct heat better than surrounding insulation. Causes hot/cold spots and energy loss.

A unit of cooling capacity equal to 12,000 BTUs per hour. A typical home needs 2-5 tons of cooling capacity depending on size and climate.

The process of making a home more resistant to weather and temperature changes through insulation, air sealing, and other improvements.

A heat pump system sized to heat the entire home, typically replacing or supplementing an existing heating system. Eligible for rebates up to $10,000 (standard) or $16,000 (income-qualified).