What is kWp in solar power?

kWp means kilowatt peak, the rated power of solar photovoltaic panels under reference conditions [S1]. For example, an assumed 100 panels rated at 0.45 kWp each make a 45 kWp array. That describes capacity, rather than annual electricity production. Ask for a separate site-specific generation estimate before assessing a business proposal. Checked October 2026.

Last checked 16 October 2026

What is kWp in solar?

kWp is kilowatt peak: a way of stating the rated power of a solar photovoltaic, or PV, array. A kilowatt (kW) measures power. The peak rating gives you a reference for comparing panel capacity; it is not a promise that your roof will produce that power throughout the day [S1].

For your business, separate the size of the proposed array from the electricity it is expected to deliver. Panel orientation, shading and local sunlight affect the estimate. PVGIS lets you model production for a location, panel arrangement and assumed system losses [S2].

How much electricity does installed capacity produce?

Here is an illustration, not a quote. Assume you install 100 panels, each rated at 450 watts peak:

• Array capacity = 100 × 450 ÷ 1,000 = 45 kWp.
• Assume a site-specific yield of 900 kilowatt-hours (kWh) per kWp each year.
• Estimated annual energy = 45 × 900 = 40,500 kWh.

The panel count, rating and yield are assumptions. The arithmetic illustrates how a capacity rating and a generation forecast fit together; the yield needs checking for your roof. PVGIS provides monthly and annual production estimates, rather than treating peak power as continuous output [S2].

What should you request with a solar quote?

Ask for the panel schedule, total kWp, inverter output, monthly generation estimate and the assumptions behind it. Also request a comparison with your electricity use during opening hours. This gives you something useful to discuss alongside the commercial solar sizing guide.

Use kW versus kWh to check the units in proposals. If charging vehicles is part of the project, compare the proposed generation pattern with your load profile.

Next step

Bring your roof details and electricity bills to get matched with an installer that covers your area. Piggy Pineapple Ltd operates this referral service. We refer enquiries to installer partners and may be paid a fee. Our owner holds shares in at least one partner. Before sharing your details, we name the proposed partner and disclose any shareholding in it.