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What does kWp and kWh mean?

Solar PV

Solar electricity systems are given a rating in kilowatts peak (kWp). This is essentially the rate at which it generates energy at peak performance for example at noon on a sunny day. The kWp of a domestic system will vary depending on how much a customer wants to spend and the roof area available to accommodate the panels.
The total amount of electricity the system actually generates in a year is measured in kilowatt hours (kWh). This will depend on the system’s orientation, shading and how sunny your site is, as well as the size of the system (in kWp) that you have installed.

A typical domestic system is between 1.5 to 3kWp. Each kWp should generate around 800 to 850kWh per year if unshaded and perfectly south facing with a tilt of around 30-50°. A solar roof array would typically generate 1200 to 2400kWh per year depending on size.

By contrast an average home uses 4000kWh of electricity per year on lights and appliances. However, an energy efficient home using A rated appliances and lighting could conceivably use half this value.