LED or LCD displays: the cost savings equation

lenovo L2251 eco displayA colleague asked me if it was worth switching from LCD displays to the newer, lower power but more expensive LED variety. Good examples of 22″ widescreen displays from our usual supplier are:

Using my PC power saving spreadsheet and assuming typical ‘office’ work patterns:

  • An LCD system (computer + screen) would use 197.8 kWh per year
    (107.8 kg CO2, £23.74)
  • An LED system (computer + screen) would use 164.8 kWh per year
    (89.8 kg CO2, £19.77)

Note that the savings (from 39W to 21W in use, or nearly 50%) don’t produce quite as dramatic a reduction as you may have expected, because we are assuming that the computer power use stays the same (typically  around 48W in use)

So we’re saving 33kWh, 18 kg CO2 and £4 electricity per year per monitor. Over a 5 year life, the electricity saved just about balances the higher purchase cost, but we would also save 90 kg CO2. The cost of carbon is currently set at £12 per tonne, so 90kg is equivalent to a £1.08 saving.

Of course if electricity prices rise (a safe bet) and carbon costs rise (likely) then tangible savings might be made. More important is the HEFCE requirement on the University to reduce its carbon footprint and our consequent Carbon Management Plan. iSolutions manages around 8000 computers, so if just 25% of those have more efficient screens, the annual saving would be around 36 tonnes of CO2. Not much in the grand scheme of things (the 2005/06 baseline of 51,878 tonnes) but these new monitors would be contributing more than their fair share to the 20% reduction we are aiming for.

There is one more reason to pick the LED monitors over the LCD, and that is that they also have some other excellent green credentials. As the Insight webpage puts it:

The ThinkVision L2251x wide is Lenovo’s greenest and most ergonomic monitor ever and the world’s first TCO certified edge monitor at the cutting edge of environmental responsibility and usability. Pioneering the use of the latest recycling technologies, 30% of the total weight of all plastics in the product consists of post-consumer content plastic resins. The product also has 92% recycled plastics in packaging materials, a protective bag that is reusable, in addition to mercury-free, arsenic-free glass and low halogen. It is 33% more energy efficient than conventional monitors (29.7% more efficient than Energy Star 5.0 standard), has Ambient Light Sensor and Proximity Sensor that further conserves energy, and has an integrated webcam that helps boosts productivity saving traveling time and expense. The L2251x wide is a perfect choice for environmentally-conscious users seeking cutting edge productivity boost. The incorporated ThinkVantage design enhances usability and makes the monitor easy to use. As defined by EPEAT verification criteria for calculation of post-consumer recycled content. Many plastic parts used in this product consists of (by weight) 65% post-consumer content from sources like home appliances, computers, vehicles, and office equipment and 20% post-industrial content.

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