If cellphone chargers waste over 1 TWh/yr, how much energy is leaking out of other devices in U.S. households?
We could not find enough reliable data on the number and usage of light fixtures to study lighting.
We were able to study consumer electronics. The Energy Information Administration produced a lengthy study on the types of appliances and electronics in American homes [n.d., Table US-1]. Many other sources detail wattages and average kWh/yr consumed by various devices [Ames City Government 2002; Seattle City Light n.d.; ABS Alaskan n.d.; Fry 2006; Dot-Com Alliance n.d.; MacKay 2008; afterdawn.com 2007; Fung et al. 2002].
However, Roth and McKenney [2007] was by far the most thorough. The only major consumer electronics that they did not report on were digital TVs, and they could also provide only yearly consumption estimates for component stereos, printers, and modems. We checked all of their data against the other sources and filled in the gaps with corroborated data and estimates. We also updated the study (completed in January of 2007) as best we could, especially considering VCRs and game consoles, whose use has changed drastically in the last two years. Table 7 shows total consumption by all electronic devices by type, with relative numbers of each device taken into account.
We offer a few notes on some kinds of devices.
• Analog TVs: They waste 4 W when turned off.
• Digital TVs: There is huge variation in wattage, from 100 W to 500 W.
CNET.com [n.d.] shows an average for new HDTVs of 250 W, with standby power 1 W. We assume that in most cases the digital TV, being
Table 7.
Annual electricity consumption of consumer electronics (TWh).
Active Idle Off Total
Analog TVs 43.6 n/a 6.4 50.0
Digital TVs 37.8 n/a 0.4 38.2
Desktop computers 20.2 0.1 1.0 21.3
Set-top boxes 6.4 n/a 13.3 19.7
Compact audio 1.4 0.9 3.8 6.2
Component stereo 1.5 0.9 2.9 5.3
Game consoles 1.7 2.4 0.7 4.8
DVD players 0.5 1.2 2.6 4.3
VCRs 0.2 0.6 2.5 3.3
Laptop computers 2.3 0.1 0.4 2.8
Modems 0.7 n/a 1.8 2.5
Home theaters 1.5 0.6 0.1 2.2
Printers 0.3 0.5 0.2 1.0
the newest TV, would be used the most; so we apply usage data from Roth and McKenney [2007] for the most-used TV. About 19.25 million flat-screen TVs have been sold since the study was done, meaning that there are now 59.25 million digital TVs in the country [Burritt 2009].
• Desktop computers: We combine CRT and LCD monitors into a weighted total, taking into account time spent in screensaver and standby modes.
• Set-top boxes (cable, satellite, and other TV boxes): These waste more energy than any other type of electronics device—a surprising fact, since there are almost a million fewer set-top boxes than analog TVs—because they still use 15 W when off, presumably to stay in contact with the service provider and in some cases to perform services (e.g., to turn on at a certain time to record a show).
• Compact audio: We use data from Roth and McKenney [2007].
• Component stereo: Roth and McKenney [2007] estimated that a compo-nent stereo uses 115 kWh/yr, with an installed base of 50 million units.
We decided that a stereo would have a usage pattern similar to a compact audio system, with wattage more like a home theater; we calculate that a stereo uses about 105 kWh/yr.
• Game consoles: Roth and McKenney [2007] reported only 2.6 TWh used by game consoles, with 1.0 TWh in active state, 1.3 in idle, and 0.4 while off. But game consoles have not only become more popular since Jan-uary 2007, but the proportion of older-generation consoles to new ones has also gone down. This is important because newer ones are consid-erably more power-hungry. Roth and McKenney reported an average of 36 W for consoles, but multiple sources cite the new Xbox 360 at 173 W, the Playstation 3 at 190 W, and the Nintendo Wii at 18–19 W. Roth and
McKenney reported 64 million consoles, but since then Wiis have jumped from 1.5 million to 13.5 million, Xbox 360s from 4.8 million to 11.9 mil-lion, and PS3s from 0.8 million to 5.9 million [Brightman 2008]. With these 24 million new game consoles, we estimate that 12 million older ones have been removed from use. So, there are now about 52 million older consoles averaging 36 W, plus 12 million new Wiis at 19 W, 7 mil-lion new Xboxes at 173 W, and 5 milmil-lion new PS3s at 190 W. Weighting appropriately gives current average wattage at 56 W.
• DVD players: They waste a staggering 87% of the energy that they use.
• VCRs: This was another area where we felt we had to correct for the two years since Roth and McKenney [2007]. They cited 5.0 TWh used by VCRs, but the number of VCRs in use has dropped since. Data from previous studies cited by them indicate that the number of VCRs de-creased by 11.25% per year from 2001 to 2005. We extend this trend to the end of 2008, for an estimate of 71 million VCRs operational today. We also adjust their usage numbers downward by 15% to account for more families preferring to use a DVD player.
VCRs turn out to be the energy-wasting champion by percentage, wasting over 95% of the energy that they consume.
• Laptop computers: Surprisingly efficient, laptops as a whole used one-seventh as much electricity as desktop computers, even though there are only twice as many desktops. A laptop uses only use 25 W while active instead of the 75 W that a desktop uses, despite the fact that the laptop wastes 18% of energy compared to only 5% for the desktop.
• Modems: Left on all the time, they have a low wattage (7 W), for 55 kWh/yr, close to the 53 kW of Roth and McKenney [2007]. Assum-ing that modems are used 6 hr/d (about 25% less than computers), only 0.7 TWh/yr is used by modems while people are actually connected to the Internet; the other 1.8 TWh lost as waste could be saved if people would unplug modems not in use.
• Home theater: This was one of the most efficient devices when off, prob-ably due to Energy Star standby-power guidelines, since they are rela-tively new devices.
• Printers: Printers on average are in use for only a few minutes per day, but their idling wattage is quite high. A reasonable average is 300 W active and 12 W idle [Dot-Com Alliance n.d.]. Assuming that a printer is used 5 min/d and left on 4 hr/d, a printer would use 34 kWh/yr, close to the estimate of 30 kWh/yr of Roth and McKenney [2007].
This analysis reveals that it is the TV complex, not the computer complex, that is responsible for the bulk of waste: 4.7 TWh idling and 26.1 TWh off for TV-associated devices vs. 0.7 TWh idle and 3.5 TWh off for computer-associated devices.
If the TV and related devices were plugged into a power strip that was turned off when the electronics are not in use, households would use 18%
less energy on electronics. Since the average household uses 11% of its energy on household electronics, this would represent a 2% reduction in overall residential electricity usage. A power strip could even be fitted with a remote-control switch—the strip would consume slight standby power waiting for the remote signal, but the devices plugged into it would not.
This would be a convenient way to turn off electronics that would also save electricity.
In all, this selection of household electronics consumes 169 TWh/yr of electricity, or the equivalent of 99 million bbl/yr of oil—considerably more than the 1.3 TWh/yr wasted by cellphone chargers. Of the 169 TWh, 125 TWh is for devices in use, 7 TWh idle, and 37 TWh waste. By percentage, 26% of a house’s energy spent on electronics is wasted: 22 million bbl/yr of oil wasted by standby power and 4 million by electronics on but idle. David MacKay attempted to minimize his standby power waste by unplugging everything he could, finding that he could save 1.1 kWh per day [2009].
Our data suggest that the average American could save just about as much (376 kWh/yr, or 1.0 kWh/d) by doing the same.
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Advisor Michael Hitchman, with team members Benjamin Coate, Nathaniel Landis, and Zachary Kopplin.
Modeling Telephony Energy Consumption
Amrish Deshmukh Rudolf Nikolaus Stahl Matthew Guay
Cornell University Ithaca, NY
Advisor: Alexander Vladimirsky
Summary
The energy consequences of rapidly changing telecommunications tech-nology are a significant concern. While interpersonal communication is ever more important in the modern world, the need to conserve energy has also entered the social consciousness as prices and threats of global climate change continue to rise. Only 20 years after being introduced, cellphones have become a ubiquitous part of the modern world. Simultaneously, the infrastructure for traditional telephones is well in place and the energy costs of such phones may very well be less. As a superior technology, cellphones have gradually begun to replace the landline but consumer habits and per-ceptions have slowed this decline from being an outright abandonment.
To evaluate the energy consequences of continued growth in cellphone use and a decline in landline use, we present a model that describes three processes—landline consumption, cellphone consumption, and landline abandonment—as economic diffusion processes. In addition, our model describes the changing energy demands of the two technologies and con-siders the use of companion electronics and consumer habits. Finally, we use these models to determine the energy consequences of the future uses of the two technologies, an optimal mode of delivering phone service, and the costs of wasteful consumer habits.
The UMAP Journal 30 (3) (2009) 353–365. c!Copyright 2009 by COMAP, Inc. All rights reserved.
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Introduction
The telephone has become a fundamental part of our social fabric. In the past couple of decades, we have seen a shift from fixed landline telephones, generally one per household, to individual ownership of cellphones. We attempt to determine the impact of this change on American energy con-sumption.
The factors that go into accurately modeling telephony energy consump-tion are complex. We need to take into account also the energy consumpconsump-tion of peripheral devices, such as answering machines for landline phones and chargers for cellphones. Moreover, landline phones are not a uniform prod-uct. Cordless phones consume considerably more energy than their corded counterparts. Likewise, the total energy cost of cellphone usage is com-plicated by such factors as recharging, replacement, and battery recycling.
Our model takes all of these factors into account, and additionally attempts to use the limited real-world data available to chart the changes in each of these factors over time.
Perhaps the most complex factor to model is adoption of technological innovations in a population. This is relevant not only to landline adoption and cellphone adoption, but additionally de-adoption of landline phones in the face of cellphone usage can be considered an independent innovation and modeled accordingly. Research into the phenomenon indicates that it can be modeled globally by the differential equation
dP
whereP is the proportion of the population that has adopted the innova-tion at timet,r is the adoption rate, and K is the saturation point for the innovation.
Using the descriptions of such a model, we arrive at an accurate fit to available data and can predict future demand for cellphones and landlines.
Determining the cost for these respective technologies we arrive at the total energy burden. Briefly, we explore how this question relates to the en-ergy consumption of other household electronics, and how much waste is generated therein. Additionally, we explore the caveat that technological development has been and continues to be wildly unpredictable, and the consequences of this reality.
A separate question is how best to distribute landline and cellphones throughout a population committed to neither, so as to minimize energy consumption while not violating social preference. This problem is ex-plored through an optimization with respect to energy usage, in which we discover that a country, here a “Pseudo-U.S.,” which supports a cellphone-only communicative infrastructure minimizes its total energy consumption, and also does not violate social demand for novel technologies. Finally, we
estimate the total energy consumption by such a nation over the next 50 years.
Model Overview
We examine two approaches to modeling technology diffusion through a population. The first attempts to gauge technology adoption at the house-hold level and aggregate these results to model global trends. However, this approach is unsuccessful, and we explain why. The second approach models technology adoption at the global level; it
• accurately models past and present telephony energy consumption,
• makes future predictions of cellphone saturation and landline de-adoption consistent with previous technological replacement paradigms, and
• encompasses a broad range of pertinent factors in telephony energy con-sumption.