Summary
Computers cost almost nothing compared to other seemingly low-energy-use household products, such as coffee makers and ceiling fans.
Would you have predicted that? I sure wouldn’t have. Before this basic exercise, that is…
The Details
Let’s compare electricity use levels among two common household products. You can easily find these numbers matched elsewhere, as well as on their manufacturer’s sites and labels on the product themselves. This is how much electricity each device pulls from the wall when it’s in use (not just when it’s plugged in):
- Laptop computer: 45 watts
- Coffee maker: 900 watts
But how often are these devices used? “Surely, Tyler,” you say, “even though the coffee maker uses significantly more electricity while actually in use, the laptop is used significantly more often. Shouldn’t that outweigh the coffee maker’s abhorrent electricity draw?” Let’s find out…
Average time usage for Internet among teens is 31 hours/week. Even though that’s not all on laptop computers (teens are well-known for their smartphone usage), let’s be liberal with our numbers. If we assume 4 hours/day, 7 days/week, that comes out to 28 hours/week. I doubt you’ll find an average American who uses their computer more than 28 hours/week.
To figure out total kWh used/year, we use this formula: Total hours used each year * device watt use /1000.
Then, we simply multiply the result by the cost of a kWh. In 2009, the average US residential electricity rate was $.11/kilowatt-hour (kWh)1.
So our resulting formula is: Yearly cost = ((Total hours used each year * device electricity usage /1000) * $.11)
The math quickly paints a much clearer – and gently disturbing – picture:
- Laptop computer: (1456 hours * 45 watts) / 1000 * $.11 = $7.21/year
- Coffee maker: (260 hours * 900 watts) / 1000 * $.11 = $25.74/year
Electricity for the laptop costs only $7.21/year.
Electricity for the coffee maker costs $25/year. The coffee maker is only used 5 hours weekly, whereas the laptop is used 28 hours weekly. The laptop is used 5.6x as often. And yet you pay 3.6x as much for the coffee maker’s electricity.
Clearly, neither device is burning a whole in your utility bill. Hopefully you see how bad we all are when predicting costs. On top of that, basic awareness of electricity consumption is a homeowner’s responsibility. More importantly, it’s your duty as a responsible citizen and human being.
Bonus
For those interested, here are the numbers for desktop computers. Desktop computer hardware is more powerful than laptop hardware; hence, it will use more power, much the same as a Hummer uses more fuel than a Prius. Or rather, it uses it more inefficiently.
Total electricity usage by (typical) desktop computers – like laptops – is still significantly less than coffee makers.
- Desktop computer: 150 watts (Asleep: 1 watt)
- Desktop computer: (728 hours * 150 watts) / 1000 * $.11 = $12.01/year
Other good resources on this topic
- http://michaelbluejay.com/electricity/howmuch.html
- http://www.tpcdb.com/
- http://michaelbluejay.com/electricity/computers.html
Next Week’s Article
Do I need to put my computer to sleep?