When the monthly rates & taxes bill arrives, many of us are gobsmacked looking at the price of electricity and the cost of running a home. Where does it all go?
How to conserve energy may seem like a complicated challenge, but working out your home or business’ power consumption is not that tricky. It just requires a bit of auditing your electrical appliances, then making a few quick sums. Doing so is not only worthwhile if you aim to save money, but will also be incredibly useful when buying a generator.
There are numerous measures for power, all of whom can be explored in our handy guide to electrical jargon. But you only need to use one measure to determine the cost of electricity: the Watt.
Most electrical items are marked with Watts – a number with a big W at the end. If that is not available, you can multiply the amps (A) and volts (V) to get the Watts. Alternatively you can consult an electrical chart such as this to see the average Watts of common items.
Working out consumption
Once you have the Watts, working out how much running that device costs you is not difficult.
Let’s start with a device quite common everywhere, at the office or part of the cost of running a home: the kettle. At the bottom you should see the watts: in this example our kettle is 1850-2200W.
Why are there two numbers? The first number represents the average use of Watts when you run the kettle, but the second number shows the peak use. This kicks in when you start the kettle.
For the sake of simplicity, let’s say our kettle averages 2000W. Now we need to work out how many watt-hours is used every day. Assuming this is a busy kettle that is used twenty times a day and it takes six minutes to boil water, that comes to two hours of use in a day:
6 minutes x 20 uses = 120 minutes
120 minutes equals two hours. Now we multiply the amount of watts to the hours, so:
2 hours x 2000 watts = 4000 watt-hours per day
But electricity is sold in kilowatts, so we need to convert this number. A watt is 1/1000th of a kilowatt, so we divide the watt-hours:
4000 watt hours / 1000 = 4 kilowatt hours
So our kettle, which is used for 6 minutes at a time, 20 times a day, uses 4 kilowatt hours (kWh) per day. Assuming this is a kettle at an office, it will be used every workday, so 5 days a week or around 20 days a month:
4 KwH x 20 days = 80 kWh per month
Now we have a number we can work with. Unfortunately there is no flat rate for electricity in South Africa: it depends a lot on how much you use per month, whether you are residential or business, etc. So you will need to scrutinise your bill for such detail.
But let’s assume for this exercise that you pay R1,10 or 110 cents per kWh. The next step, thus, is:
80 kWh x 110 cents = 8800 cents or R88 per month.
Pick a room
The next step in working out the cost of running a home or office is to decide what you want to quantify. You could look at all the lightbulbs or work out how much your television consumes in a month. But the best approach to go room by room: choose a location, take stock of the electrical appliances in there and estimate how often they are used. Then apply the above calculations.
Don’t forget about the hidden appliances, such as geysers or security system batteries. Figuring out their consumption may not be as clear cut, but at least you can get a general idea. Above all, though, you may be surprised how much electricity everyday appliances such as office equipment or air conditioners can use.
Use Online Calculators
There are several electricity calculators you can use to help determine electrical usage…
This breaks down usage per appliance:
If you want to switch between watts and kilowatts per appliance, this calculator will help:
For an overall consumption, this electricity cost calculator is best. It gives results per unit, but it’s not a change. One unit = one kWh: