When looking into solar panels, you’ll see two important metrics – KWh and KWp. Both refer to energy and power output but have different meanings. Understanding the difference between KWh and KWp is important when determining what size solar system you need. This article explains what KWh and KWp mean, how to calculate KWp and the relationship between KWh and KWp.
What is KWh?
KWh stands for kilowatt-hour and is a measure of energy over time. Specifically, it refers to the amount of energy used or produced in one hour. For example, if a 100-watt light bulb is left on for 10 hours, it has used 1,000 watt-hours or 1 kilowatt-hour (kWh) of electricity (100 watts x 10 hours = 1,000 watt-hours = 1 kWh).
When talking about solar panels, KWh refers to the energy output over a period of time, usually per year. For example, a 5 kilowatt (kW) solar system may produce 8,000 kilowatt-hours (kWh) of electricity annually. The kWh produced over a year is important for estimating how much electricity the solar panels will generate and offset from your utility company.
What is KWp?
KWp stands for kilowatt-peak and refers to a solar panel system’s maximum potential power output under ideal test conditions. It measures the instantaneous power, not over time. For example, a 5 KWp solar system can deliver 5,000 watts of power at peak performance.
KWp is commonly used to rate the power and size of solar panel systems. It represents the maximum possible power output, but the actual output will be lower depending on environmental factors like sunlight and temperature. KWp gives an idea of how many panels are needed to meet energy needs.
The Relationship Between KWh and KWp
While KWh measures total energy production over time and KWp measures peak power, they are related. The KWh output of your solar panels depends on the size of KWp. However, the kWh per KWp, or the solar panel yield, can vary.
Here’s an example to illustrate:
– A 5 KWp solar panel system
– With a solar panel yield of 1,500 kWh per KWp per year
– Would produce 7,500 kWh in a year (5 KWp x 1,500 kWh/KWp = 7,500 kWh)
So for a given system size in KWp, the kWh production per year depends on the estimated solar panel yield. Solar panel yields vary and depend on location, climate, sunshine hours, and panel efficiency. So while a 5 KWp system may produce 7,500 kWh in one climate, it could produce 9,000 kWh in another sunnier location.
How to Calculate Solar Panel KWp
When designing a solar panel system, you must determine the right KWp to meet your energy needs. Here are the steps to calculate KWp:
1. Estimate your annual energy usage (kWh per year)
Review 12 months of past electric bills to get your annual kWh consumption. Only look at usage, not the costs. You can also use an online calculator to estimate usage based on home size and appliances.
2. Determine the solar panel yield for your location (kWh/KWp)
Use solar maps to estimate the average annual solar production in kWh for each KW of solar panels. This varies by location and climate.
3. Divide your annual kWh by the solar panel yield.
For example, if you use 12,000 kWh per year and the solar yield is 1,500 kWh/KWp, you would need an 8 KWp system:
12,000 kWh / 1,500 kWh/KWp = 8 KWp
This calculates the approximate system size needed to offset your annual usage, though some extra capacity is recommended. Solar installers can help pick the right system size.
KWp Meanings Summary
– KWh = Kilowatt-hour, a measure of energy produced or consumed over time. Used to measure solar panel electricity production per year.
– KWp = Kilowatt-peak, a measure of the maximum potential power output from a solar panel system under ideal conditions. Used to rate solar panel system size and capacity.
– KWh per year depends on the KWp system size and your location’s estimated solar panel yield.
– To right-size your system, calculate KWp based on your annual energy usage divided by the solar panel yield.
Understanding the difference between KWh and KWp is key for properly sizing and evaluating solar panel systems. While KWh measures annual energy output, KWp is a better indicator of solar panel system size and capacity. The KWp calculation using your location’s solar panel yield helps ensure your solar panels meet your electricity needs.