Solar panels on a house convert sunlight into electricity. A typical system has 1 main conversion stage: an inverter changes the panels' direct-current (DC) electricity into alternating-current (AC) electricity for the home. Extra electricity can charge a battery or flow to the utility grid. When solar production falls short, the home draws electricity from the battery or grid.
A Home Solar System at a Glance
| Component | What it does |
|---|---|
| Solar panels | Convert sunlight into DC electricity |
| Inverter | Converts DC electricity into AC electricity for household appliances |
| Electrical panel | Sends electricity to the home's circuits |
| Utility meter | Measures electricity bought from or sent to the grid |
| Battery, if installed | Stores solar electricity for later use |
| Utility grid | Supplies electricity when solar production is insufficient |
How Solar Panels Produce Electricity
Solar panels contain photovoltaic, or PV, cells. Each cell uses semiconductor material, usually silicon, to absorb energy from sunlight.
When sunlight reaches a PV cell, its energy causes electrons in the semiconductor to move. That movement creates an electric current. Multiple cells connect to form a panel, and multiple panels form a rooftop solar array.
The electricity produced by the panels is direct current, or DC electricity.
Why a Solar Inverter Is Needed
Most household appliances and the utility grid use alternating current, or AC electricity. A solar inverter converts the panels' DC electricity into AC electricity that the home can use.
A house may use either:
- A string inverter, which converts electricity from a group of panels in one central location
- Microinverters, which attach to individual panels and convert electricity at the panel level
Microinverters can help when panels receive different amounts of sunlight, such as when part of a roof is shaded.
How Solar Electricity Powers Your Home
After the inverter converts the electricity to AC, the electricity flows into the home's electrical panel. The panel distributes it to lights, outlets, heating and cooling equipment, appliances, and other circuits.
In practical terms, electricity is used in this order:
- Solar electricity powers appliances operating in the house.
- Excess electricity charges a connected battery, if available.
- Remaining excess electricity flows to the utility grid.
- If the home needs more electricity than the panels are producing, the home draws the difference from the battery or grid.
Solar panels do not need to power each appliance separately. The system connects to the home's electrical system, where the electrical panel distributes power across the house.
What Happens to Extra Solar Electricity?
Solar panels can produce more electricity than the house is using, especially during sunny periods when household demand is low.
The extra electricity may flow to the utility grid. Depending on the state and utility company, the homeowner may receive a bill credit through net metering or another solar compensation program. Credit rates, eligibility rules, and system limits vary by utility and location.
A battery stores surplus electricity for use later in the evening, overnight, or during a power outage.
How Solar Panels Work at Night and on Cloudy Days
Solar panels produce electricity when they receive sunlight, but production falls when sunlight is weaker. At night, the panels do not produce electricity.
A grid-connected home normally gets electricity from:
- Solar panels when sunlight is sufficient
- A battery after it has been charged
- The utility grid when solar and battery power are insufficient
Cloudy weather does not necessarily stop solar production, but reduced sunlight usually lowers output. Roof orientation, shading, panel angle, system size, and local weather also affect production.
Will Rooftop Solar Work During a Power Outage?
Solar panels alone usually will not keep a grid-connected house powered during an outage.
Most standard grid-tied solar systems automatically shut down when the utility grid fails. This protects utility workers who may be repairing power lines.
A solar system can provide backup power when it includes a battery and an inverter designed to operate independently from the grid. The battery and system controls isolate selected household circuits from the failed grid, allowing the system to supply those circuits safely.
A backup system may power essential loads such as:
- Refrigerators
- Lights
- Internet equipment
- Medical devices
- Selected outlets
It may not run every appliance indefinitely. Large loads such as electric heating, air conditioning, water heaters, and electric vehicle chargers can use substantial power.
What Affects How Much Electricity a House Produces?
A home solar system's output depends mainly on:
- The number and power rating of the panels
- The roof's direction and angle
- Shade from trees, buildings, or roof structures
- Local sunlight and weather
- Panel temperature and condition
- Inverter and system losses
- Household electricity use
A south-facing roof is often productive in the Northern Hemisphere, but east- and west-facing roofs can also work well depending on the roof design and when the household uses electricity. An installer should evaluate the roof and model expected production before sizing the system.
The Simple Version
A rooftop solar system works like this:
Sunlight → solar panels → DC electricity → inverter → AC electricity → home appliances
When the panels produce more electricity than the house needs, the surplus goes to a battery or the utility grid. When the panels produce too little, the home uses stored electricity or power from the grid.