Average Electricity Wastage at Home Assessed — I Did the Math
By: Audrey Hmt
Tags: Climate Action, Environment, Energy, Sustainability, Emissions

How do we often waste electricity at home?

In a simple model I built, there are 5 common energy waste categories and in which we can easily reduce our emissions by being mindful and aware of it. Calculations and assumptions are my own, with figures taken from various sources and appropriately referenced in the model.² Let’s start off with the obvious ones that most of you might already know about.

1. Air conditioning

According to a study conducted in South Africa, increasing the temperature set-point by 1°C could reduce the average annual energy usage by 7.92%. Many others often estimate similar percentages as well.

If we take an average of 13.5 kwh/m² annual electricity usage on ACs in Shanghai as a proxy, an increase of 3°C could amount to an annual decrease of 64 kwh for the average person in shared housing, or 44 kwh for a person living alone in a studio. The difference could be greater in different areas of the world where the average electricity usage on ACs is higher. This adjustment is also even more effective when the outside temperature is higher, as it could also decrease the amount of degree days. Important to note is that there were no significant heat waves at the time of the study yet — nowadays occurring more frequently. Temperatures have been rising in general as well, so the potential impact could be more far reaching.

2. Central heating

Similarly to ACs, a different temperature set-point by 1°C could lead to an annual 13% reduction of energy. The average EU dwellings use 125 kwh/m² electricity in a year — if we decrease the heating by 2°C, it could lead to a 661 kwh reduction for a person in shared housing and 456 kwh for a person living alone.

3. Laptops and Desktop Computers

Although the following categories don’t have huge numbers like ACs and heating, it does stack up over time and possible reductions are not disturbing at all. Let’s assume a person living alone has 1 laptop, and a household has 3 laptops and 1 desktop.

The first one is sleep mode drainage. Both Windows and Macs go into sleep mode by default, and go into hibernate or standby mode after 3 hours of sleep. Though energy usage in sleep mode is less than when in use, it still drains the battery slightly as it does not close down the applications that are running. Laptops usually use 2W in sleep, and the average of desktops is at 7.5W. By contrast, hibernate or standby uses no power as it turns off but keeps the running applications in temporary RAM storage. When you want to continue your work, everything will still be there. So when we close down our PCs before ending our day, it wastes energy for 3 hours every day. For a laptop, this leads to an annual wastage of 2.2 kwh, and 8.2 kwh for a desktop. For a person in a shared household, this could save 3.7 kwh annually.

And now I’m sure we’re all guilty of the second one; stepping away from your PC for a short bit while taking a break, getting snacks, or anything else really. If we do this several times a day, it might amount to 15 minutes per day. With an average laptop energy usage of 35W and desktop computer of 115W, this totals to 3.2 kwh per laptop and 10.5 kwh per desktop PC annually. So, a person in shared housing could save 5.2 kwh. More often than not, we leave our PCs on for way longer periods than 15 minutes a day thinking it won’t make a big difference. But this does stack up over time.

4. Vampire Energy

Vampire energy drains electricity from our homes without us noticing. A charger left plugged in can drain 1.5 kwh annually. We assume that a person living alone keeps 2 chargers plugged in, and in shared housing 5 chargers as they might share some in the shared spaces. For the person alone, this would be 3 kwh annually, and a person in shared housing 1.9 kwh.

More notably, we waste a lot of energy through standby modes of appliances. These are often left on standby, with people thinking they are turned off. However, they are still on and ready to receive signals from remotes whenever and continue to drain energy. The perpetrators are anything with a remote, or any kind of digital clock. Although a lot of progress has been made to reduce their usage by regulations such as the one from the European Commission that limits it to a maximum usage of 0.5W, this still adds up. If a person living alone has 2 things left on standby — a microwave and one other appliance, it adds up to 8.8kwh annually. In a shared housing, we assume there are 6 appliances kept on standby — a microwave, TV, TV box, printer, coffee machine, and a stereo system. This would be an annual usage of 6.6 kwh per person.

5. Lights

Modern LED lightbulbs don’t waste a lot of energy anymore. But if we assume a person living alone leaves the lights on while moving and switching from room to room for 10 minutes per day, and 30 minutes per day in a shared household, it also adds up. With a LED lightbulb of 15W, this could be 0.7 kwh per year per person in shared housing, and 0.9 kwh per year for those living alone.

Another thing to note is that you could save a lot if you downgrade the number of lumens on your lightbulb. This determines how much light you get, the brightness. If you switch your bulb from 1250+ lumens to 500 lumens, and assume 3 hours daily light usage for those living alone, we can save 11 kwh annually. If we take 8 hours of light usage for those in shared living taking into account common room and private room lighting, this adds up to 7.3 kwh per person.

Lastly, if you still use CFL bulbs at home… You’re probably in for even more. Make the switch to LEDs right now.