GLOSSARY
This page provides descriptions of common terms related to energy efficiency.
AIR SEALING
The process of locating and blocking gaps, cracks, and holes in a home's building envelope (walls, floors, and ceilings).
BATTERY STORAGE
A home battery storage system captures and retains electricity (from solar panels or the grid) for later use. It boosts energy efficiency by allowing you to store surplus power for use during expensive peak hours or outages, rather than relying on grid power.
BTUs (BRITISH THERMAL UNIT)
BTUs measures your equipment's heating or cooling capacity. Specifically, it measures the rate at which your equipment generates heat or removes heat per hour.
COP (COEFFICIENT OF PERFORMANCE)
COP is a measure of how efficiently heating and cooling systems, like heat pumps and air conditioners, operate. COP is measured as a ratio: the amount of heating or cooling produced per electrical energy consumed.​
Example: If a heat pump consumes 1 kilowatt (kW) of electricity to deliver 3 kW of heat, its COP is 3.0. (This means the heat pump is producing x 3 more heat than the electricity it takes from the grid)​
CONTRACTOR
Also referred to as vendors, contractors are professionals that diagnose, design, and install upgrades to improve a home's thermal performance, comfort, and energy usage.
CAPACITY
Capacity is a measure used to size heating and cooling systems. If the capacity is lower than the heating or cooling load, the system will struggle to reach the design temperature; if it's too high, it will cycle on and off too frequently (short-cycling).
Cooling Capacity:
The amount of heat an air conditioner or heat pump is capable of removing from a home per hour. Measured in BTUs.​
Heating Capacity:
The amount of heat a heating system is capable of transferring or producing per hour. Measured in BTUs.​
DESIGN TEMPERATURE
Outdoor and indoor design temperatures are metrics used to size heating and cooling systems.
Outdoor Design Temperature:
Extreme local weather thresholds used to calculate the absolute heating or cooling capacity a home requires.
Indoor Design Temperature:
The standard, comfortable indoor temperatures that a home's system is expected to maintain.
ELECTRIFICATION
Home electrification is the process of transitioning a household's energy consumption from fossil fuels (like oil, natural gas, and propane) to clean, electric-powered systems​ (like heat pumps and induction stoves).
ENERGY AUDIT
A home energy audit is an inspection and evaluation of a property to identify energy waste, air leaks, and heating or cooling inefficiencies. See the Getting Started section for more.
ENERGY EFFICIENCY
Home energy efficiency means using less energy to perform the same household tasks and maintain comfort.
HOME ENERGY UPGRADE
When we talk about home energy upgrades, we are commonly referring to the changes that make your home more energy efficient, such as weatherization work or installing heat pumps. The process of upgrading a building with new technologies or materials is also called retrofitting.
IAQ (INDOOR AIR QUALITY)
IAQ refers to the management of fresh air, moisture, and pollutants in a home. See the Air Quality Considerations section for more.
KILOWATT (kW) & KILOWATT-HOUR (kWh)
kW:
Indicates the amount of electricity required to run your appliances (1 kW = 1,000 watts).
kWh:
The total amount of electricity used over a period of time (kW × hours = kWh). Example: An AC unit that draws 4 kW for 3 hours consumes 12 kWh of power.
LOAD
Cooling Load:
The amount of heat that must be removed from a space to maintain a comfortable, steady indoor temperature. Measured in BTUs.​
Heating Load:​
The amount of heat required to add to a home to maintain a comfortable temperature.Measured in BTUs.
NET ENERGY BILLING
Also called net billing, Net metering is an offset a customer may receive on their electricity bill for selling excess electricity from a solar system to the grid.
R-VALUE
Measures the resistance of materials (like insulation) to heat flow. Higher R-values means less heat flow.
THERMAL PERFORMANCE
Describes how well your house retains heat in the winter and blocks heat in the summer. Thermal performance is evaluated through specific metrics and testing, often via an energy audit.
U-VALUE
Measures the rate of heat transfer (loss or gain) through a building component, such as a window or wall. Lower U-values indicate less loss or gain.