Computers
Below are frequently asked questions about the energy consumption of computers.
Q: I am interested in finding out if a computer is considered a high-energy
user compared to other appliances, such as a toaster or hair dryer. Are any comparisons
available?
A: Computers and their peripherals by themselves are not large
energy users. However, if left on for long periods of time, their operating expense
can add up. A computer, monitor and printer consumes about 750 Watts, so one hour
of operation in the summer will cost about $.06. Therefore, running your system a couple
of hours a day will cost about $3.60 per month. However, if you run the system 24 hours
a day, it will cost about $43 per month.
While toasters and hair blowers consume more power -- 1,200 Watts and 1,000 Watts
respectively -- their use is so short that the cost to operate them is minor. For example,
a hair blower running for two minutes would cost about $0.0027.
Q: About half of computer experts suggest turning your computer off to save
power if you are not going to use it for several hours. The other half say keep it on.
So about how much does it cost to run a typical home computer consume for eight hours
with the monitor turned off?
A: To come up with an accurate answer, I started out by asking three
major computer manufacturers this question and received an "I don't know" answer from
each. So, I conducted my own consumption test using a Watt recorder. I ran the computer
with both the processor unit and monitor on and then with just the processor.
Together, the processor and monitor consume 121 Watts.
121 Watts x 8 hours per day = 968 Watts, divided by 1,000 = .968 kWh x $0.065 = $0.063 per day
(average).
The processor only, without the monitor, consumed 38 Watts.
38 Watts x 8 hours per day = 304 Watts, divided by 1,000 = .304 kWh x $0.065 = $0.020 per day
(average).
So, running your system with the monitor on will cost about $.06 per day for eight hours, while
the same system running with the monitor turned off will cost about $.02 per day for eight hours.
Q: We are on SRP's Time-of-Use price plan, which offers lower prices for electricity
during certain times of the day. On this plan, which method will use less electricity in the long
run: starting up the computer during off-peak hours and shutting it down before on-peak,
turning it on again only after 8 p.m., or starting it up during off-peak and leave it running all
day if we intend to use it again during the same day?
A: To save energy and reduce costs, the best way to operate your
computer system is to turn it on when you need it and off when you don't. A middle-of-the-road
computer and monitor will consume about .13 kW per hour. Therefore, if you turn it on and let it
run for 24 hours it will cost about $0.25 per day, or $7.54 per month.
If your computer has an energy savings or "sleep" mode, this consumption and cost can be
reduced to .042 kW per hour, which amounts to $0.08 per day and $2.40 per month.
Keep in mind that printers and scanners can easily double these costs if they are left on.
