The kWp meaning is simple: kWp stands for kilowatt-peak, the rated power of a solar system under standard test conditions. It tells you how big the system is, not how much electricity it will produce. A 6 kWp system has panels whose combined lab rating is 6 kilowatts. How much energy it actually produces over a year, measured in kWh, depends on where you live, which way the panels face, shade and weather.
kWp meaning vs kWh: capacity vs energy
The easiest way to understand the kWp meaning is to compare it with kWh.
Term
What it measures
Example
kWp (kilowatt-peak)
The system’s rated power: its size
“A 6 kWp system”
kWh (kilowatt-hour)
Energy produced or used over time
“It produces about 7,000 kWh a year”
Think of kWp like the size of a water pipe, and kWh like the amount of water that flows through it over a year. A bigger pipe can move more water, but how much actually flows depends on conditions.
“Standard test conditions” are lab conditions used to rate every panel the same way. On a real roof, panels rarely hit their full rating for long, and output varies with the sun’s angle, temperature, snow and cloud.
How kWp turns into kWh where you live
To estimate yearly production, multiply the kWp by how much one kWp produces per year in your area. Natural Resources Canada publishes this figure for thousands of municipalities in its photovoltaic potential maps. For south-facing panels tilted at the latitude angle:
City
kWh per kWp per year
A 6 kWp system produces about
Regina
1,360
8,160 kWh
Calgary
1,291
7,750 kWh
Winnipeg
1,272
7,630 kWh
Ottawa
1,200
7,200 kWh
Montréal
1,190
7,140 kWh
Toronto
1,163
6,980 kWh
Halifax
1,073
6,440 kWh
Vancouver
1,007
6,040 kWh
Estimates for well-oriented, unshaded panels. East- or west-facing and shaded roofs produce less.
Why the kWp meaning matters when you compare quotes
Price: quotes are often expressed in dollars per watt. A 6 kWp system at $2.80 per watt costs $16,800 before incentives. (Illustrative price; use your own quote.)
Sizing: kWp is how installers size a system to your usage.
Fair comparison: two quotes with the same kWp can promise different kWh. Ask each installer for estimated annual production in kWh, and how they calculated it.
How to work out the kWp you need
Find your yearly use on your bills or your utility account, in kWh.
Look up your local production per kWp from NRCan’s maps.
Divide: yearly use ÷ production per kWp = system size in kWp.
Count panels: kWp ÷ panel rating in kW. For example, 400 W = 0.4 kW.
Hypothetical example: a Toronto home uses 9,000 kWh a year. 9,000 ÷ 1,163 ≈ 7.7 kWp. With 400 W panels, that’s about 19–20 panels.
Gradual panel degradation over the years, as stated on the panel warranty
Good installers include these factors in their production estimate.
The bottom line
The kWp meaning comes down to this: it’s the size of your solar system, not its output. Multiply kWp by your local production figure to estimate kWh, compare quotes on both kWp and kWh, and use your own usage to decide how big a system you need. To weigh cost against savings, try our solar ROI calculator in Excel or see how much a 5 kW solar system produces.
Frequently asked questions
What does kWp mean in solar?
kWp means kilowatt-peak: the rated power of a solar system under standard test conditions. It describes the system’s size, not how much energy it produces.
Is kWp the same as kWh?
No. kWp is capacity (power), while kWh is energy produced or used over time. A 6 kWp system in Toronto produces roughly 7,000 kWh a year, according to NRCan’s data.
How do I calculate the kWp I need?
Divide your yearly electricity use in kWh by the yearly production per kWp for your location, from NRCan’s photovoltaic potential maps.
Can I increase my system’s kWp without adding panels?
Not usually. kWp is the combined rating of your panels, so increasing it means adding panels or replacing them with higher-rated ones.
