Electrical power is how much a solar system produces at any given time, and it is measured in W (a kW is 1000W). A solar system’s potential power is also measured in kW – i.e. a 10kW system is a system with panels that can produce up to (and sometimes slightly more than) 10kW of DC electricity.
Electrical energy is measured in Wh (a kWh is 1000 Wh). The amount of electricity that you use at home is measured in kWh on your electricity bill. The amount of electricity that your solar system produces, or is capable of producing, in a given period of time is also measured in kWh.
The amount of energy that any given solar system can produce depends on the location of the system, and specifically the amount of sun that location gets. For example a 10kW solar system in southern Australia, or northern USA, with a perfect installation, may expect around 35kWh of energy on average per day throughout the year. Whereas a 10kW system in northern Australia or southern USA may expect 55kWh a day on average throughout the year.
There are actually lots of factors that determine how much energy a solar system can produce. They include:
- Sunlight – PV (or photovoltaic panels) require light to produce energy. Factors that decrease sunlight are:
- Dirt – Dirty panels obstruct sunlight and reduce power output.
- Shade – Trees or buildings can get in between sunlight and your panels.
- Heat – You might expect heat to help in solar production, actually heat is detrimental to the output. The best conditions are lots of light, and low heat.
- Installation of the solar panels – The angle relative to the suns path, and the azimuth (direction the panels face) are a big factor in the ability of the panels to produce power.
There are other factors that matter, and I’m sure I’ll get a few electricians or engineers posting corrections. Please do!
W = watt
kW = kilowatt
kWh = kilowatt hour
DC = direct current
*The other form of electricity being AC (alternating current). Solar systems produce DC, the inverter turns that into AC, which can be used in your home.