The 96-hour energy efficiency ‘audit’ of the Smith family

Meet the Smith family – They ‘Know their Number’, and it is 75.

This case study revealed that the Smiths, just as many others residing in the Bedfordview and Edenvale area, are guilty of leaving bathroom lights on, wasting water by washing hands with warm water,  filling the kettle for one cup of coffee, and the list goes on…

Does this sound similar to your household? By examining the Smiths’ behaviour, we can all learn some valuable lessons for a guilt-free, energy-saving experience during our daily, busy lives and schedules.

So, what is all the fuss about knowing your number?

Everyone wants to save electricity! After all, every little bit helps. Any saving effort you make not only helps you have more money available for the small little luxuries in life, but also contributes significantly to reducing the environmental impact your consumption has. This is where Knowing Your Number comes in handy – it provides you with a starting point to set out on the path to becoming energy efficient.

The figure provided by the Know Your Number formula is an Energy Rating and indicates your electricity use based on your house size.

Using a practical example, the Smith’s consume 7184 kWh per year, based on the units indicated on their municipal account statements. The livable space under roof in their home is 96sqm. 7184 kWh/96sqm = 75 kWh/sqm/year, so their energy rating is 75 which places them in a C category on our rating scale. To improve their cost savings, the Smiths need to set themselves a target. Let us pin the target at saving 25%, so they need to reduce their electricity savings by 1⁄4.

To help the Smiths identify why their number is this high, we placed several CCTV cameras in their home to identify their good and not-so-good energy behaviors.

Here is what we found:


In the passage

The first camera catches the Smiths leaving the bathroom light on for five minutes, despite no-one using the facilities. However, Mom Tracey comes to their rescue and switches it off as she passes by.

In the kitchen

Here everyone (including Mom) is guilty of wasting water – and electricity – by washing their hands with hot water, which is not necessary. This no doubt contributes to the Smith’s geyser consumption of about 12.7kWh per day, or 4635kWh a year, which is equal to more than half of their overall electricity consumption in a year. Using cold water saves huge amounts of electricity. A Solar Water Heater (SWH) would save them even more as it only consumes 5.2kWh a day, equal to 1898 kWh a year, which will have a significantly impact on your finances. The info bar below shows how they could save over R4,000 each year by installing a Solar Water Heater.


Still in the kitchen…

The Smiths wash their dishes by hand, which means that they use hot water from the geyser. Investing in an A+++-rated dishwasher will not only save energy, but will also allow them to sit back after dinner and enjoy some family time.

In the lounge

After washing dishes, our cameras catch Mom Tracey leaving the kitchen light on when she goes off to pack clothes away. The 18-watt CFL light bulbs in the kitchen (of which there are 4) means that they use 4 x 18 watts for every hour that they leave it on.

If the lights are left on unnecessarily for one hour a day, it equates to about 27 kWh for the year that are simply wasted. Switching to LED bulbs could save the Smiths 350kwh per year. Run your mouse over the info bar below to see how their savings are calculated.



Back to the kitchen

We find that Tracey wastes electricity by using a pot that does not match the size of the stove plate. Placing the lid on the pot would also increase the cooking pressure, thereby reduce cooking time.

Still in the kitchen…

Dad Wayne leaves the fridge door open for four minutes while discussing with Mom Tracey what they should have to drink. Virtually all the cool air escapes from the fridge, which means the fridge motor has to work at its peak to recover all that cold air.

Run your mouse over the info bar below for more cooking tips.


As the family sits down for dinner, they are so keen to get stuck into Mom’s delicious meal that they forget the lights on in the kitchen. Being energy efficient is not a natural behavioural process for us, so practicing this over time will have a lasting impact on our behaviour.

If you enjoy a good cup of coffee after dinner, remember to only fill the kettle with the amount of water you need. Boiling more water than is required is wasteful.

Back in the lounge

Our lives are very busy so it becomes more and more difficult to spend quality time with your loved ones. Using dinner time to catch up on what happening in your family’s lives is much more impactful than catching up on the latest soap. Switch off the TV and have some real fun.


In the passage

The bathroom light was left on for 30 minutes without anyone going in – this is a long time and the amount of electricity wasted adds up to be significant!

The laptop and other gadgets

Our cameras catch Mr Smith getting up from where he is working on his Laptop and leaving the TV on for more than 30 minutes. All appliances left on standby continue to consume a lot of electricity, and end up being unnecessarily wasteful.


In the laundry

Today we observe the domestic worker ironing. There are so many items in that laundry basket that can easily be folded up without having to be ironed. Doing this saves electricity. We’ve calculated that the Smiths waste 114kWh of electricity each year through leaving the iron on. Iron clothes that are required to be ironed, on the hottest setting first, and then turn the iron down to the cooler settings to iron more fragile clothes.


Still in the laundry…

Front-loader washing machines are more efficient than top loaders, and if you are in the market for a new one choose one with an A+++ rating as they are most efficient. Remember to load your washing machine to full capacity as this reduces the number of loads to wash, which obviously saves electricity. View other valuable power-saving tips in the info bar below.


In conclusion…

The Smiths have some bad behavioral habits that can easily be changed to save them a lot of money.

Their current energy rating is 75 kWh per sqm per year. This places them in the C- rating category and that means they can do a lot more to reduce their energy rating. If we include all the potential savings the Smiths could make by adopting energy efficient habits, they would save as much as 3410 kWh per year.

The 3774 kWh/96sqm equals 39 kWh per sqm per year. This means the Smiths move from a C category to a B category. So, their rate is on average R1.54 per unit, meaning that if they save 3410 kWh per year, they save R 5251.40 per year!

And just think what they can do with that extra money, especially with Christmas around the corner. Challenge on!

About 49M: The 49M campaign was launched in March 2011 as a response to the country’s constrained power system. The campaign encourages individuals and corporates to lead energy smart lifestyles thereby saving the planet and their pockets. South Africans are encouraged to join the campaign by visiting to pledge their support. Go to the 49M Facebook page or tweet @49m_Co_Za.

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