kW vs kWh in solar, explained with your electric bill
kW is how big a system is (its power at full sun). kWh is how much energy it makes over time — the unit on your bill.
A kilowatt (kW) is a rate: how fast energy flows. A kilowatt-hour (kWh) is an amount: 1 kW flowing for 1 hour. Your utility bills you in kWh; installers size systems in kW.
Solar panels are rated in watts of direct current (DC) under a lab standard of 1,000 W/m² of sunlight at 25 °C. A “7 kW system” is 7,000 W of panel ratings added up — a peak number it rarely reaches on a real roof.
The link between the two is the location’s yield: how many kWh each kW of panels makes in a year. In Seattle that is roughly 1,100 kWh per kW; in Phoenix nearer 1,750. The same 7 kW system therefore makes very different amounts of energy in different places.
Batteries use both units too: kWh is how much they store (a Powerwall 3 holds 13.5 kWh) and kW is how much they can deliver at once (11.5 kW continuous) — which decides whether they can start an air conditioner.