How rooftop solar works, in the time it takes to boil a kettle
Four pieces of equipment, one meter and a set of rules. That is the whole system.
The equipment
Panels turn sunlight into direct current (DC). A typical new panel is about 1.7 by 1.1 metres and rated 400–450 watts.
Inverters turn DC into the alternating current (AC) your home uses. Either one box serves the whole roof (a string inverter), or a small inverter sits under each panel (microinverters).
Racking bolts the panels to the roof. Monitoring reports what the system makes, usually on your phone.
kW and kWh, the two numbers on every quote
A kilowatt (kW) is the size of the system: its output in perfect, cool sunshine. A kilowatt-hour (kWh) is energy: what your bill charges for. A 7 kW system in Phoenix makes about 12,500 kWh a year; the same system in Seattle makes about 8,000. Size is what you pay for; kWh is what you get. More on kW vs kWh.
What happens in a blackout
Ordinary grid-tied solar switches off when the grid goes down, so it cannot feed power onto lines that line workers are repairing. To keep power during an outage you need a battery, or an inverter with a sunlight-only backup socket. Chapter 7 covers batteries.
Watch: the best short video on this step
More in solar videos and resources.
Checklist for this step
- I can explain the difference between kW (size) and kWh (energy)
- I know that solar without a battery does not work in a blackout