Solar terms homeowners should know

You do not need to be a solar expert to compare a proposal. Start by checking what the system is supposed to include, how its production was estimated, and who will handle utility and permit steps. The terms below help you ask for the same information from each installer.

This guide is for a homeowner reading a rooftop solar proposal. The practical answer is to use these words to compare written scopes and to flag any term that a proposal leaves unexplained. Your next action is to ask each installer to define their assumptions in writing.

Terms to recognize

Kilowatt (kW): A kilowatt measures power at a moment. In a solar proposal, kW usually describes the system’s rated size, not the amount of energy it will make in a year.

Kilowatt-hour (kWh): A kilowatt-hour measures energy over time. Your electricity bill and a solar production estimate often use kWh, so compare the same periods rather than treating kWh as the system’s size.

Module or panel: The surface that converts sunlight into direct-current electricity. Ask for the model name, quantity, and wattage rating so you can confirm what the proposal actually lists.

Inverter: Equipment that changes the panels’ electricity into electricity that the home and grid can use. Inverter choices can affect what equipment is included and how the system is monitored, so the proposal should name them.

DC and AC: Direct current (DC) is the electricity produced by panels; alternating current (AC) is the form used by typical home wiring and the grid. This distinction helps you understand why inverters and other electrical equipment appear in the scope.

System size: The combined rating of the panels or a related proposal-design measure. Ask whether the number is DC kW of panels or AC rating of the inverter, because these measures are not interchangeable.

Production estimate: A modeled forecast of electricity the system may generate over a period, often a year. It depends on site, shade, weather, equipment, and model assumptions; it is not a guarantee of bill reduction or performance.

Shade and shade analysis: Shade is the sunlight blocked by trees, buildings, chimneys, or other obstacles. A shade analysis is the installer’s method for building that exposure into the production estimate; ask what site data and assumptions it uses.

Interconnection: The utility’s process for reviewing and approving a system that connects to the grid. Rules, timing, fees, and required paperwork depend on the utility and location, so ask who submits it and what might change the project schedule.

Net metering or net billing: A utility billing arrangement for energy your system exports to the grid and for energy you buy. The name, credit rate, eligibility, and rules vary by utility and can change; do not treat a proposal projection as a promise.

Permit: Local authorization to do installation work. A proposal should say which permits the installer intends to handle and any conditions that could require a revision.

Rack and mounting: The rack is the frame that secures panels to the roof; mounting is how the rack and panels are attached and sealed. Ask how the written scope addresses roof penetrations, flashing, or open roof conditions; do not inspect or probe them yourself.

Rapid shutdown: A safety function that reduces or controls voltage in the solar array when the system is required to shut down. Ask the installer to explain the equipment and who will test and document it; do not attempt to activate it yourself.

Battery and backup loads: A home battery stores electricity; backup loads are the specific circuits or appliances the design intends to supply during an outage. A battery does not automatically mean whole-home backup; ask what loads and limits the proposal actually includes.

Degradation: A modeled decline in a panel or battery’s expected output or capacity over time. It is a projection based on product terms and assumptions, so read the warranty document and ask what measurement and redress it actually provides.

Warranty: A written promise from a manufacturer or installer about defined coverage. Separate panel, inverter, battery, roof-penetration, and workmanship warranties, and ask who makes a claim and what can void coverage.

Use the terms to compare proposals

Ask each installer to map the proposal’s system size, production estimate, shade assumptions, equipment models, permits, and interconnection steps to the same property. Then compare written scopes for mounting, electrical work, utility paperwork, warranties, and change-order process. For a step-by-step framework, read How to compare solar installation proposals. You can also use How to prepare for rooftop solar to gather the information that makes that comparison more useful.

Questions to ask your solar professional

1. Is kilowatt size in this proposal the panels’ DC rating, the inverter’s AC rating, or both, and what production assumptions go with it?
2. Which shade, utility, interconnection, and permit assumptions could change this proposal or its schedule?
3. What equipment, roof-mounting work electrical work, testing, and warranty responsibilities are included, and what is excluded?

Sources

• U.S. Department of Energy, Homeowner’s Guide to Going Solar (retrieved October 1, 2026).
• U.S. Department of Energy, Solar Photovoltaics (retrieved October 1, 2026).
• Federal Energy Regulatory Commission, Interconnection and Net Metering (retrieved October 1, 2026).

Be ready for the conversation

3 questions to ask your solar installer

1. 1What annual production are you estimating for this roof, and which assumptions drive it?
2. 2What equipment, roof work, electrical work, permitting, and utility coordination are included?
3. 3What could change the price or design after the site visit, and how will you document it before work begins?