Watt

A watt (W) is the standard unit of measurement for electrical power. It represents the rate at which energy is produced or consumed at any given moment.

In solar energy, watts are used to describe the power output of individual solar panels under standard test conditions. A typical residential solar panel produces 350–450 watts. When you see a panel rated at “400W,” it means that panel can generate 400 watts of power at peak sunlight. System sizes are usually expressed in kilowatts (kW), where 1 kW equals 1,000 watts. The cost of solar is often quoted in dollars per watt ($/W) — for example, $2.75/W means a 8,000-watt (8 kW) system would cost $22,000 before incentives. Understanding watts vs. watt-hours is important: watts measure instantaneous power, while watt-hours measure total energy produced or consumed over time.