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LCD vs CRT Energy Consumption A Market Study Prepared for Dell Computer by Mark Fihn DisplaySearch October 29, 2001 What Others Are Saying… Photon Dynamics Presents to White House
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A Market Study
October 29, 2001
Photon Dynamic’s VP of Marketing, Bruce Delmore, advises President Bush about the energy advantages of flat panel monitors.
Photon Dynamics’ demonstrated to President Bush on two separate occasions regarding the difference in energy consumption between a 17.0” LCD monitor versus a 19.0” CRT monitor by attaching power meters displaying watt usage. The difference in power consumption was dramatic, 73 watts. LCDs typically use approximately 30% of the power of similar CRTs. "Research shows that LCDs use about 74 percent less electricity and space, than their CRT predecessors, while reducing eye-strain and heat load," said Sollitto. "With more than 50 million CRTs in California, the state could save up to $1 billion a year or almost 5 billion kilowatt hours of its total electricity use if only half of the CRTs were replaced with LCDs," he added.
• Supply - California has the ability to generate 55.5 billion watts of power and can import another eight million watts per day. Actual capacity appears to be around 45 billion watts due to transmission losses and some plants not fully operational. For more info, see www.cpuc.ca.gov/published/report/GOV_REPORT.htm.
• Demand - Peak energy demand in California in the winter is 45.5 billion watts while summer 2000 demand reached 53 billion watts. For more information on California's energy demand, see www.energy.ca.gov/electricity/commission_demand_forecast.htm.
• Population - 33.145 million people according to the 1999 census.
• Number of CRTs per Person – Estimated at 1.5. Includes TVs monitors, public displays, ATMs, etc., so that the number of CRTs in California is estimated at 49.7 million.
• Watts per CRT - Estimated at 115. Depends on size, brightness, etc.
• Watts per LCD Monitor - Estimated at 35. Also depends on size, brightness, LCD mode, etc.
• Watts Consumed By CRTs - 5.72 billion Watts.
• Watts Consumed if All CRTs Replaced By LCDs - 1.74 billion Watts
• Power Savings from Migrating to LCDs -3.98 billion Watts. The four billion Watt reduction would solve many of California's energy problems by reducing power consumption by 9%. It would avoid blackouts and Stage 1, 2 and 3 alerts, which are defined as statewide power reserves falling below 7%, 5% and 1.5%. The four billion Watts is approximately equal to the combined output of all nuclear power plants in California and could power four million homes.
• Price per kW/hr - $0.10 - $0.30 depending on time, type, etc. Photon Dynamics assumes $0.12 on average. Price per W/hr would then be $0.00012.
• Cost Savings Per Day - Assuming monitors are operated for eight hours per day, cost savings would be $3.8 million per day or $1.4 trillion per year.
• Percentage of Power Consumed by CRTs - Based on Charles' assumptions, CRTs consume 12.6% of the power produced in California.
-- Analysis from Charles Annis, Photon Dynamics
A recent study by Fred Cohen at the Sandia National Laboratories was conducted to solve a practical problem of determining how to get 250 computers operational in a very small area and with a limited total power capability. The office situation meant that not all of the computers could be on at the same time, meaning that different projects had to be scheduled for different times. Moreover, since system turn-on transients use more energy than when the devices operate at a steady state, meaning that a schedule had to be created to turn on/off computers appropriately. The team at Sandia solved the problems by creating a database of the power consumption and turn on transient power consumption for every device in the laboratory. The database was then used to determine how many of what kinds of computers could most efficiently go on each circuit and to schedule power up sequences associated with the different devices.
Interestingly, the creation and implementation of the Sandia database identified some fascinating global consequences related to energy consumption. First of all, the team discovered that salvaging and upgrading older computers in order to reduce computer expense budgets did not always actually save money. According to Dr. Cohen, “We would take an 8 year old display and attach a $10 connector to get a working unit for next to nothing, but the power consumption was higher than a more recent display, so we were ending up paying more for electricity than we other wise would have had to”.
But it gets worse. The more energy required for a computer system, the more heat that is generated, which increases air conditioning loads. An additional side effect of higher temperatures is a more rapid degradation of computing devices resulting in shorter lifetimes and more failures. As reported by Dr. Cohen, “Every watt of power you save in computer energy, you save again several times over in air conditioning cost…Since almost all of the energy used by computers goes to heat, we have to pay for the power we use in computers twice; once for their use and once for the removal of their resultant heat”.
Although Fred Cohen’s study evaluated all computer equipment, the most telling results related to their calculations comparing CRT monitors and LCD monitors. The study indicated that the power consumption for a flat panel monitor is about 1/5 the power consumption of a typical CRT monitor.
The higher energy costs have been used by Japanese LCD monitor brands as a means to promote LCD monitors since the infancy of the LCD monitor market due to much higher energy costs in Japan. In a study by the Electronics Industry Association of Japan in early 1999, it was shown that the average cost of operation of a 15" LCD monitor over a 5-year period was lower than an average 17" CRT monitor due to 80% lower electricity costs, 75% lower cooling equipment costs and 58% lower space costs. The biggest savings in their study were from the space costs with energy costs accounting for just 8% of the total operating cost of a 17" CRT. Nonetheless, the EIAJ study showed that if 50% of Japan's CRT monitors were converted to LCDs, four power plants and 181,000 tons of CO 2 emissions could be eliminated.
A quick comparison of IBM’s various monitor products easily shows the substantially lower power consumption associated with TFT LCDs. Even at 200 pixel/inch, the industry’s highest performance TFT LCD monitor, the T221 consumes the same amount of energy as a high-end Trinitron CRT Monitor. This is significant since the T221 offers a 12% increase in diagonal size, and 480% more information content. In other words, the viewable information on the T221 would require more than 5 of the Trinitron monitors.
Source: Dr. Martina Ziefle, Technical University of Aachen, Germany, DisplaySearch High Resolution Symposium 2001.
15.0” UXGA 22 words
15.0” XGA 12 words
Better Word Comprehension
18” Viewing Distance
Wright, S.L., et. al. (1999) SID’99 Digest, 346-349.
A 15° eye movement is generally accompanied by a head turn. Using this rule you can estimate the number of head turns required to scan a screen width from an eye point 18 inches away.
Reduced Head Turns
8.5 x 11.0” paper requires no head turns.
Paperback books are sized to minimize head turns…
Higher dot pitches mean smaller display diagonals. This means fewer head motions and stiff necks.
Based on research from NASA Ames Research Center
LCD Pixel Density Advantage
Input Fields for Energy Cost Calculator
-- Based on inputs from Dell Computer
Note: Other Calculators on the Web: