Published: September 11, 2011 11:00 PM
By Pierre-Jean Alzieu
Translated by: Sam McGeever

On the left, we have a plasma TV in the shape of the Panasonic TX-P42GT30, one of the best TVs to use active 3D TV and a great example of what plasma technology can do!
 
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On the right, LCD technology is represented by the LG 42LW550T, which has Edge LED backlighting and an IPS display.  This time round, support for 3D comes from passive technology which is easier on the eyes.

 
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Plasma | IPS
1920 x 1080 pixels | 1920 x 1080 pixels
Sizes: 42'', 46'' and 50''
| Sizes: 32'', 42'', 47'' and 55''
HDMI (x4) - Composite - Component - USB (x3) - Optical audio
| HDMI (x4) - Composite (x2) - Component - USB (x2) - Optical audio
178° / 178° | 178° / 178°


BACKGROUND

Over the past few years, manufacturers have managed to bring the energy consumption of both plasma and LCD TVs right down.  If you're just showing a still test card, then it takes about 250 W to power a 42'' plasma screen.
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LCD TVs still have something of an advantage because an average 42'' display only uses about 80 W.  Things are a little less clear cut on standby where these days both technologies use virtually no power—around 0.2 W for the vast majority of TVs.

Given how much energy consumption has fallen in the past few years, do LCD screens really still use less than their plasma cousins in the long term?  And if they do, how big are the savings you can expect?

 

TESTING PROCEDURE

We used two identical Wattmeters to measure the consumption of each TV.  The average household watches around five hours of TV a day, leaving their television on standby the rest of the time, so we chose two films and cycled them for five hours, followed by 19 hours of standby.  For theses tests, we  set the brightness to an average level of 170 cd/m² and looped Batman: The Dark Night and Monsters vs. Aliens.

We measured the energy consumption in W, and then used the average UK unit price from March 20011 of 12.04 p/kWh.  The amount you pay will, of course, vary depending on your circumstances and the electricity provider you use.

ENERGY CONSUMPTION: ONE DAY

We started both TVs in standby, and they both used around the same amount of power with only a negligible difference between them.  After 19 hours, the Panasonic TX-P42GT30 plasma had used 0.007 kWh, while the equivalent figure was 0.002 kWh for the LCD-based LG 42LW5500. 

The gap is much bigger when you switch them on: after five hours, the LG LCD had used 0.339 kWh, but the Panasonic plasma was up at 0.925 kWh.

If we assume a unit price of 12.04 p/kWh, the difference is less shocking because the plasma costs 4.08 p to run for a day, just over 7 p more than the LCD at 11.14 p per day—hardly enough to break the bank!
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Electricity costs per day (£)

consommation lcd plasma un jour
 

ENERGY CONSUMPTION: ONE YEAR

Of course, comparing these prices over a whole a year makes the difference stand out more.  Rather than just a few pennies, the difference is counted in terms of a few dozen pounds.

On average, the annual running cost for this LCD TV would be £14.89 while that figure is closer to £40.66 for the plasma.
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Electricity costs per year (£)
 
consommation lcd plasma un an

ENERGY CONSUMPTION: SEVEN YEARS

Electricity costs over seven years (£)

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The average consumer buys a new TV every seven years, so we calculated how much these two TVs would cost over that period.

Unsurprisingly, LCD won out again, costing just £104.23 over the lifespan of this LG, compared to the £284.42-worth of electricity the Panasonic plasma would have used.

VERDICT: LCD TAKES A STRONG LEAD

If anybody was still in any doubt on the matter, we can definitely say that there is a real difference between the energy consumption of plasma and LCD technology.

To produce a picture with the same brightness, an LCD TV needs around a third as much power as a plasma.
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If you watch a 42'' plasma for a year, it will cost you around £41 in electricity, compared to the mere £15 that the much more efficient LCD will set you back.

Our suspicions have been confirmed: the long-standing difference in energy consumption between LCD and plasma TVs hasn't gone away!

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