The Beginners Guide to Understanding Electricity Consumption

Electricity. We all need it. We all pay for it. Most of us would like to keep our electricity consumption (and our bills) to a minimum. But most of us also have no idea where to begin when it comes to calculating our own personal electricity expenses, or understanding how electricity consumption varies from appliance to appliance. To help you better understand your electricity consumption habits and expenses, we’ve put together a very basic guide to help you understand how your electricity bill is calculated. Woman holding lightbulb How is a unit of electricity measured? The power of electricity is measured in watts (W). While watts are used to measure the power of an electrical appliance or product, the amount of energy converted in a one hour (h) period is known as kilowatt-hours (kWh). Therefore the units of electricity we purchase in store for our paid meters or on our electrical bill are equal to the kilowatts of electricity consumed per hour. So, one unit of the electricity that we purchase is equal to 1000 watt-hours (Wh) or one kilowatt hour (kWh). By the numbers:
  • 1 unit of electricity bought = 1 kilowatt hour = 1000 watt-hours.
  • The wattage of something tells you how much electricity it consumes.
  • The higher the wattage of an item or appliance, the more electricity it uses in a standard period of time.
Watt watt How much electricity will an item or appliance use? An appliance will use its wattage worth of electricity in an hour (if left on, uninterrupted for an hour). For example, a 60 watt light bulb will use 60 watt hours of electricity in one hour. It will use 120 watt hours of electricity if left on for 2 hours, and more electricity as the time passes and it is left on to operate. The higher the wattage, the more electricity is required to run the item per hour. How is the price of electricity determined? In South Africa, the government has established an independent collective of experts who help to determine the prices we are charged by utilities such as electricity. This collective acts as a regulator and is known as the National Energy Regulator of South Africa (NERSA). It helps to determine the price of electricity by considering the cost to the supplier (as it should be if they run the company efficiently) and what a reasonable profit (rate of return) would be on the regulatory asset base. The electricity costing program established by NERSA runs according to a semi-set Multi-Year Pricing Determination (MYPD). Currently NERSA operates on a five-year (macro-style) Multi-Year Pricing Determination plan (due to end in March 2018). This is so that the increase in the cost of electricity per year is slightly more predictable. The current price for 1 unit (1 kilowatt-hour) of electricity varies based on numerous factors, but hovers at around roughly R1.50 in domestic environments. How much electricity does your home use? To simplify things and help you make educated decisions about how you choose to use your electricity, we’ve compiled a guide to estimating how much electricity your home uses on average. See the appliances below found in a common household, along with their power ratings in Watts, and follow the instructions to calculating energy consumption:

Appliance power rating (in Watts) X hours in use i.e. 40W x 2hrs = 80Wh or 0.08kWh.

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Being informed when it comes to how electricity-heavy various appliances are can help us make better informed decisions with regards to effectively saving electricity. But ultimately, the price of electricity is only set to increase with time. As a result, changing your energy consumption habits and investing in energy efficient appliances now will ultimately cut your energy bill in the long run. So the next time you purchase an appliance, do your future self (and bank balance) a favour and consider investing in a solar or alternatively powered version if possible.