Think of it like water in a hose: kW is the pressure and flow rate, kWh is how many gallons actually came out. A 7.2 kW charger running for two hours delivers 14.4 kWh of energy to your car.
In practice: your electricity bill is measured in kWh (how much energy you consumed that month). A solar installer talks in kW when describing system size and kWh when estimating annual output. Home batteries are rated in kWh (how much they store) and kW (how fast they can discharge). Getting these straight makes it much easier to compare quotes — a “10 kW solar system” and a “10 kWh battery” are very different things.
When you’re getting quotes
Watch for this in solar proposals: installers typically show system size in kW and estimated annual production in kWh. Compare the annual production figure against your actual annual consumption (found on your Duke Energy bill or account portal). For batteries, the kWh number tells you how long it can power your home; the kW number tells you how many appliances it can run at once. Both matter.
Common questions
- What's the difference between kW and kWh on my Duke Energy bill?
- Your Duke Energy bill charges you for kWh — kilowatt-hours — which is the total energy you consumed over the billing period. kW (kilowatts) is the rate of consumption at any given moment. Think of kWh as the total distance driven and kW as the speed. Duke Energy may also show a demand charge in kW on commercial accounts, but residential bills are purely kWh-based.
- How many kWh does the average North Carolina home use per year?
- The average NC residential customer uses roughly 11,500–12,000 kWh per year according to EIA data, which is above the national average of around 10,500 kWh due to higher cooling loads in summer. Homes in Raleigh and Charlotte with electric heat or a heat pump often run higher. Your actual figure is on your Duke Energy annual usage summary, which installers use to size a solar system.
- What kW solar system do I need for a home in Raleigh or Charlotte?
- A rule of thumb is to divide your annual kWh consumption by 1,200–1,400 (the typical annual production per installed kW in central NC) to get a rough system size in kW. A household using 12,000 kWh per year would need roughly an 8–10 kW system. A good installer will model this precisely using your actual Duke Energy bill and your roof's orientation and shading.