I have always had a fascination for electricity – when I finished school I spent a few years deciding whether to take a degree in electrical engineering or accounting. In the end international travel beckoned and I decided accountancy was the more portable option.
Now, as we develop Energy360 and our renewable energy solution, a key element of the discussion with clients revolves around the capacity of our renewable energy equipment and the amount of energy the client uses. Both being a different measure of electricity as explained below.
The first measure of electricity is the capacity of the system or the rate at which energy is generated or used in 1 hour. A little like the speed at which a car is driving. This is generally expressed as kW (or MW where 1,000kW equals 1MW and of course 1,000W equals 1kW.).
The second measure of electricity is the measure of the consumption of energy over a specific period of time. Similar to the measure of distance a car has driven. This is generally expressed as kWh (or MWh where 1,000kWh equals 1MWh).
Light bulbs are a simple example of these two measures. Take a 100W light bulb – you know that when powered up, it will generate 100W. Thus over a two hour period the consumption of energy will be 100W x 2 hours which equals 200Wh.
Take this example further for roof top solar panels. The average size or capacity of an Australian residential rooftop solar panel system is 5kW (source: REneweconomy July 2015). However the average Australian home has an average daily energy consumption of 16kWh (Source: Australian Energy Regulator March 2015). How does this work?
The average daily energy consumption is the total energy consumed in 24 hours, for example:
Capacity multiplied by hours used = Consumption
• The 0.2kW television on for 6 hours = 1.2kWh
• Washing machine 4.5kW doing a 1 hour warm wash twice = 9.0kWh
• The 0.05kW refrigerator on for 24 hours = 1.2kWh
• Five 0.1kW (100W) light bulbs on for 5 hours each = 2.5kWh
• The 2.0kW oven on for one hour = 2.0 kWh
The table shows us that if the total capacity of the rooftop solar panels is 5kW, then we can only run the washing machine and the lights with the solar panels (4.5kW + 0.5kW). The remaining electricity requirements of the house – will have to be sourced from the grid or not turned on when the washing machine is running because the consumption is greater than the capacity!