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Amid rising energy costs, we're motivated more than ever to switch off unused lights and electronics at home to save power. As an engineer in the electronics industry, I was curious how high these electricity costs really are. How much do we really save when we turn off our computers or TVs when not being used? And, what difference (if any) does saving power make in the grand "green" scheme of things?
With these thoughts in mind, colleagues and I began to calculate the electricity costs for common household electronic devices as well as the resulting CO2 emissions from generating this electricity. The results surprised us. For example, a 500-watt, 65-inch LCD TV left on all the time would cost the consumer $484 in electricity per year and the generation of that electricity would produce 5873 pounds of CO2 per year. In terms of carbon footprint, that's equivalent to about half a car on the road in the U.S. — a pretty significant impact.
Standby power
Switching off electronic devices may not solve the power problem completely, however, since many of our home electronic devices consume a significant amount of power, sometimes referred to as "vampire power," when turned off or in "sleep" mode. It's not just the big appliances such as TVs and stereos that consume power in standby mode. Power supplies and battery chargers, such as cell phone chargers, may also draw significant power when unused but left plugged to the wall.
Vampire power is estimated at 25 watts per home. That doesn't sound like much, but multiplied by 110 million households in the U.S., vampire power costs U.S. consumers $2.7 billion per year in electricity, requiring the equivalent of 2.5 large power plants. We estimate generating this electricity also results in 32 billion pounds of CO2, which is equivalent to the CO2 from 2.8 million cars on the road (that's about 1% of the passenger vehicles in the U.S.). In light of the impact from vampire power, it's clear that electronics manufacturers should strive to minimize not only active "on" power, but also standby or "sleep mode" power, too.
The growth of gadgets
The preceding example shows that small power savings multiplied by many units can have a significant impact. Although the average consumer may worry more about the battery life than environmental impact of their small music/game player or cell phone gadget, electronic system manufacturers and chip vendors sell millions of devices (and the power supplies/chargers that go with them), so trimming even a little bit of power from each device can make a difference.
For example, the electricity needed to power just 1000 relatively low power 1-watt electronic devices is:
1 watt x 1000 systems x 8760 hours/year = 8760 kilowatt-hours per year
Assuming electricity costs on average $0.1064 per kilowatt-hour, then the total cost of electricity is:
8760 kWh/year x $0.1064/kWh = $932 per year
Or almost $1,000 in electricity costs per year at current rates (more in the future if energy costs continue to climb). That's almost a $1 per device — and these were low power products!
Greener power
In an ideal world, we'd get all of our electricity from clean sources such as solar and wind. Unfortunately, power generation in most countries is far from green and therefore power consumption of our electronics has an environmental cost in addition to the purely financial electricity cost. In the U.S., for example, the average CO2 emission for electricity generation is 1.34 pounds of CO2 per kilowatt-hour. Therefore, the power consumed by our 1000 1-watt gadgets results in:
8760 kWh/year x 1.34 lbs CO2/kWh = 11,738 pounds of CO2 per year
This CO2 emission is solely from powering the electronic gadgets and does not include the environmental effects of manufacturing and distribution. In addition to reducing power consumption on the demand side, it's also interesting to note that technology can be applied to reduce CO2 emissions from electricity generation, i.e. on the supply side, by finding cleaner and/or more efficient ways to generate and distribute electricity.
It's hard for most people to relate 11,738 lbs of CO2 to their daily lives. We wanted to find ways of comparing this number to everyday quantities. For example, the average U.S. car emits 11,395 lbs CO2 per year, so powering a thousand, 1-watt systems from our example is equivalent to 1.03 cars on the road in terms of CO2 emissions.
Some other fun and interesting carbon equivalents can be calculated for our example from statistics found on the internet. 11,738 lbs CO2 per year equates, on average, to:
- 23.63 typical PCs (CO2 from electricity generation to power these PCs)
- 18,945 air miles flown
- 25,072 minutes showered (based on CO2 impact from heating water)
Web calculator
We found these calculations fun and interesting, so we developed a web-based calculator (figure 1) to show costs in dollars and CO2 impact for powering electronic devices. It calculates either costs or savings depending on whether you enter total power consumed or power saved.
(Click on image to make your own calculations!)
Figure 1: Electricity cost and CO2 calculator (Gadget Version)
A full version of the calculator is also available at www.national.com/co2calculator, which lets you enter your local electricity utility rate as well as device duty cycle (what percentage of the time the electrical device is actually on).
Industry change
Electrical power consumption of our electronic appliances and gadgets does have a real cost in terms of dollars as well as environmental impact. With rising energy costs, consumers are motivated to buy lower-power electronics and turn them off (or put them into sleep mode) when not being used. But the electronics industry can play a major role in reducing consumer energy costs, as well as the impact on the energy grid and environment.
Here are some things National Semiconductor is doing to address these issues from both the electricity demand and supply perspectives:
- Energy-efficient PowerWise solutions with clearly labeled power/ performance specifications
- Enable more efficient and cleaner generation of energy through SolarMagic technology
Even with small changes in consumer behavior, improved electronic systems design and chip technology, and with improved energy generation, it all adds up to be a big difference. Milliwatts do matter.
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