Energy TermsGlossary
Understanding the language of solar, HVAC, and home energy solutions
20 terms found
Air Sealing
The process of identifying and sealing air leaks in your home's envelope to prevent heated or cooled air from escaping. Critical first step before insulation.
Example:
Air sealing can reduce heating and cooling costs by 15-20%.
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BLS (Bureau of Labor Statistics)
The U.S. government agency that tracks economic data including electricity prices. Their historical data shows consistent increases in energy costs over time.
Example:
BLS data shows electricity costs increased from $0.062/kWh in 1978 to $0.25/kWh in 2025.
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Battery Storage
A system that stores excess solar energy in batteries for use during nighttime, cloudy days, or power outages. Provides backup power and energy independence.
Example:
A home battery system like Tesla Powerwall can store 13.5 kWh of energy.
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Energy Assessment
A comprehensive evaluation of your home's energy use identifying opportunities to save energy and money. Mass Save offers these for free.
Example:
A free Mass Save energy assessment includes blower door tests and instant savings measures.
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Federal Tax Credit (ITC)
A federal tax incentive that allows you to deduct a percentage of your solar installation costs from your federal taxes. Currently 30% through 2032.
Example:
For a $30,000 solar system, you can claim a $9,000 federal tax credit.
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Grid-Tied System
A solar system connected to the utility grid that can both draw power from and send excess power to the grid. Most common residential setup.
Example:
Grid-tied systems automatically switch to grid power at night when panels aren't producing.
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Heat Pump
An efficient electric heating and cooling system that transfers heat rather than generating it. Can reduce heating costs by 50% compared to oil or propane.
Example:
Ductless mini-split heat pumps are popular Mass Save upgrades for Massachusetts homes.
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Inverter
A device that converts DC (direct current) electricity produced by solar panels into AC (alternating current) electricity used by your home and the electrical grid.
Example:
The inverter is typically installed on the side of your house or in your garage.
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kWh (Kilowatt-Hour)
A unit of energy equal to 1,000 watts used for one hour. This is how utility companies measure your electricity consumption and what appears on your electric bill.
Example:
If you run a 100-watt light bulb for 10 hours, you've used 1 kWh of electricity.
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Mass Save®
A state-sponsored program offering Massachusetts residents rebates, incentives, and no-cost services to improve home energy efficiency and reduce utility bills.
Example:
Mass Save offers up to $10,000 in rebates for heat pump installations.
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Net Metering
A billing mechanism that credits solar system owners for excess electricity they add to the grid. When your panels produce more than you use, the meter spins backward.
Example:
With net metering, excess solar production during sunny days offsets your usage at night.
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PPA (Power Purchase Agreement)
A financing arrangement where a third party owns the solar system on your property and you buy the electricity it produces at a fixed rate, typically lower than utility rates.
Example:
With a PPA, you pay $0 upfront and immediately start saving on electricity.
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Payback Period
The amount of time it takes for your energy savings to equal your initial investment in a solar system or energy efficiency upgrade.
Example:
With current incentives, most Massachusetts solar systems have a payback period of 6-8 years.
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Production Estimate
A calculation of how much electricity a solar system will generate based on location, panel orientation, shading, and weather patterns.
Example:
A south-facing 6 kW system in Boston produces approximately 7,200 kWh per year.
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ROI (Return on Investment)
A measure of the profitability of an investment, calculated as the net gain divided by the initial cost. For solar, this includes energy savings, tax credits, and increased home value.
Example:
Solar systems typically provide a 10-20% ROI over their lifetime.
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Rate Escalation
The annual percentage increase in utility electricity rates. Historically averages 3-5% per year, with recent years seeing higher increases.
Example:
If rates increase 5% annually, a $200 monthly bill becomes $325 in 10 years.
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SREC (Solar Renewable Energy Credit)
A certificate that represents the environmental benefits of generating 1 MWh (1,000 kWh) of solar electricity. SRECs can be sold to generate additional income.
Example:
Massachusetts homeowners can earn additional income by selling SRECs generated by their solar systems.
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Solar Panel (PV Panel)
A device made of photovoltaic cells that converts sunlight directly into electricity. Also called a photovoltaic (PV) panel or module.
Example:
A typical residential solar installation has 15-30 solar panels on the roof.
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System Size
The total power output capacity of a solar system, measured in kilowatts (kW). Typical residential systems range from 5-10 kW.
Example:
A 7 kW system typically produces 8,000-9,000 kWh of electricity annually in Massachusetts.
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Utility Rate
The price your utility company charges per kWh of electricity. Rates typically increase annually and vary by time of day and season.
Example:
Massachusetts average utility rate is around $0.25/kWh as of 2025.
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