Saving on electricity: Understand what your appliances are costing you
When we talk about electricity, we refer to energy in Kilowatt-hour abbreviated as kWh. kWh implies a Kilo (that is 1,000) Watts of power for one hour. Note the use of power and energy: Think of power as the speed at which you use energy. So power, multiplied by the time in hours, is the total energy you use in kWh.
In terms of cost a kWh from Eskom costs between R1.70 and just over R2, let’s work on R1.80 per kWh as an example. So if your pool pump uses 1.1kW and you run it for four hours per day, it will cost you about R7.92 per day (for 4.4kWh). If you want to conserve energy, you have to think of how much power each appliance uses, and the length of time you use it.
Some devices, for example a kettle, uses 2kW but we only use it for three minutes at a time, so boiling a kettle takes 0.1kWh to boil, costing you 18 cents. The geyser is a special case, and deserves to be a topic on its own, but the next worst device at home is a tumble dryer. It uses about 2.8kW and you run it for say 40 minutes. That would be 1.87kWh or R3.36.
Notice that all these amounts are small; the problem is they add up. Lights are a good example, let’s say you have a room with six halogen down lights, and you switch them on for five hours per day. That would be 50 Watt x 5 hours x 6 lights = 1.5kWh or R2.70. Now do that in four rooms for 30 days then it becomes R324 per month.
I get irritated at energy conservation campaigns telling us to unplug things like cellphone chargers. It’s a waste of advertising time to “educate”, which can be put to better use. My charger uses less than 25 cents per month if it is left plugged in all the time.
So, in general, devices that are used to heat up anything use the most power and devices that have electric motors are next. Then there are lights, which use less power, but stay on for long, and lastly electronic devices. For example: a 42 inch LCD TV plus a DStv decoder left plugged in for 18 hours per day while you don’t use it, costs R30 per month.
Reproduced here with the kind permission of GreenPro Consulting
Who is Marius Fourie?
Marius Fourie is a consulting engineer specialising in renewable energy systems and power optimisation. Marius studied Engineering at the University of Stellenbosch and is registered as a professional engineer with the Engineering Counsel of South Africa. He is also a certified energy manager at the International Association of Energy Engineers. He has many years management and technical experience across a number of sectors including energy, industrial process control, IT and communication where he has delivered many large projects. Find out more about Marius and GreenPro Consulting here.