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Q: LCD vs CRT monitors in terms of energy savings ( Answered 5 out of 5 stars,   3 Comments )
Subject: LCD vs CRT monitors in terms of energy savings
Category: Computers > Hardware
Asked by: beta-ga
List Price: $10.00
Posted: 18 Apr 2002 16:08 PDT
Expires: 18 May 2002 16:08 PDT
Question ID: 1082
How long would it take to recoup the additional cost of an average 17" 
LCD monitor versus an average 17" CRT monitor judged from the amount 
on energy saved by using the more efficient LCD unit?
To put it a different way:  I'm interested in knowing more than just "LCD 
monitors are on average 30% more efficient", I'd really like to know how 
that additional efficiency translates into money saved and how long it 
would take to get that money back in saved energy bills.
Subject: Re: LCD vs CRT monitors in terms of energy savings
Answered By: bunny2-ga on 19 Apr 2002 18:04 PDT
Rated:5 out of 5 stars
Hi there –

You asked for specific information regarding the energy cost savings and pay-
off time for a flat screen vs. a CRT monitor.  As has come up in several 
comments, there are many specific factors that go into calculating this 
answer.  Among them are:

Time Usage – how often your monitor is on (and for a CRT is it asleep or 
awake?), hours used per day, days used per year
Energy usage – the wattages of the specific two monitors you wish to compare
Local energy costs – the cost charged per kW by your electric provider

While I cannot answer your question exactly (without further details), I can 
tell you how to make the calculation yourself.

First, you need to calculate the kW used per year for each monitor.  The energy 
usages can then be converted into costs by multiplying by your energy rate.  
The difference between the two costs reflects the cost savings you will recoup 
after using a flat screen (instead of a CRT) for one year.  You can apply this 
annual savings to the price difference between the two models to determine how 
long it will take to pay off the more expensive flat screen.

kW saved per year
The Energy Efficiency and Renewable Energy Network (EREN) is part of the US 
Dept of Energy.  At the EREN website they list the wattage of many appliances.
The wattage of a CRT monitor is listed as 150 watts (awake) or 30 (asleep).  
This means that in energy use, one hour of awake time = five hours of sleep 
time for the EPA example monitor.

According to IBM, the T Series flat panel monitors consume 3-4 watts asleep and 
30 – 65 watts awake. 
Note that the awake energy use changes by a factor of more than 2, depending on 
screen size.  For a flat screen monitor which uses 3.5 watts (asleep) and 50 
watts (awake) 1 hour of awake time = 14 hours of sleep time.

For an example solution (for a CRT) see below:

Time Use – hours/day:  6.5 (to account for sleep time)
Time Use – days/year: (52weeks/yr – 2weeks vacation/yr) x (5days/wk) = 250 
Monitor Watts: 150
Cost per kWh: $0.07

[(hours/day) x (days/year) x (watts)] / 1000 watts/kW = annual kWh consumption

(kW) x ($/kWh) = annual energy cost

[(6.5hr/day) x (250days/yr) x (150watts)]/1000 = 243.75 kWh annual energy 
(243.75 kWh) x ($0.07/kWh) = $17 per year
A CRT monitor costs $17 per year in electricity.

Using the above calculations for a flat screen monitor with the following data:
Time Use – hours/day:  6.2 (to account for sleep time)
Time Use – days/year: (52weeks/yr – 2weeks vacation/yr) x (5days/wk) = 250 
Monitor Watts: 50
Cost per kWh: $0.07
A flat panel monitor costs $5.40 per year electricity.

To do this yourself
To determine the exact answer to your question, perform the above calculations 
for each of the two monitors, and compare your results.  To determine your 
annual energy usage, use the wattage values printed on the back/bottom of the 
two monitors you are comparing.  To determine the Time Usage for a CRT that 
goes to sleep, use an average value of time based on the % time the monitor is 
Additional Information
Many resources can be found where the energy efficiency of flat screen monitors 
is touted.  Several of these sites are mentioned in the comments.  Others are:
UC Irvine News, March 14, 2001

National Renewable Energy Laboratory

Other Notes:
Be careful when using specific energy savings figures from a Manufacturer.  As 
shown above, there are many factors that go into these final figures, so 
anything quoted is just an estimate, and Manufacturers have an incentive to 
make their product more attractive.

While some of the energy used by a CRT is generated as heat, a CRT is generally 
not as efficient as a real heater.  For heating purposes it will still be more 
efficient to spend those kW on a heater not a CRT.

While the EPA Monitor Power Management Calculator is helpful in computing cost 
savings on the basis of certain criteria, this calculation does not allow you 
to calculate costs based on monitor type.

I used the following search terms: flat, screen, panel, monitor, “energy use,” 
efficiency, watts, utility, cost, electricity

Enjoy your new monitor! (whether it's a flat screen or a CRT) 
While it doesn't add to the energy savings, the flat screen sure looks cooler :)
beta-ga rated this answer:5 out of 5 stars
very thorough, thanks

Subject: Re: LCD vs CRT monitors in terms of energy savings
From: blader-ga on 18 Apr 2002 17:54 PDT
Hi! I believe I may be able to help you with this question.

Your question was how much money a LCD monitor saves in terms of energy costs 
over CRT monitors. The exact number depends on how often you use your monitor 
per day, as well as the energy costs per kilowatt in your local area, but I 
did find these statistics helpful:

According to, a monitor manufucturer, you will 
receive the following savings from the purchase of an LCD monitor over a CRT 
monitor. Keep in mind that these are on average, and the source may not be an 
impartial one.

$55 per year energy savings compared to CRT monitors
$550 savings due to space efficiency.

According to NEC-Mitsubishi's figures, each 5 watts of power consumption costs 
about a dollar per year. Using the 49-watt MultiSync LCD1830 as an example, 
the yearly LCD energy cost is about $10; the cost of a typical 19-inch CRT, 
which draws about 140 watts, would be $28. Over a period of five years, 
savings would add up to $90. Unfortunately, the retail cost of the LCD1830 -- 
one of NEC's "aggressively priced" models -- is $1,899, which is well over $90 
more than you'd pay for a comparable CRT. 

Google Search Terms Used: lcd monitor cost savings

Hope that helps!
Subject: Re: LCD vs CRT monitors in terms of energy savings
From: geo-ga on 18 Apr 2002 22:58 PDT
Energy savings can be a thorny problem to calculate completely. The extra 
energy consumed by a CRT monitor does not disappear. It is radiated into the 
room in the form of heat.

If it is winter, and you are otherwise heating the room with an electric heater,
you will require less electricity to heat the room when using a CRT monitor, so 
there may, in fact, be no total energy saving.

But if it is summer, and you are air conditioning the room, the savings
from using a cool LCD display will be both the electricity saved per hour to 
run the monitor and the savings gained from requiring less air conditioning to 
achieve comfort.
Subject: Re: LCD vs CRT monitors in terms of energy savings
From: dumdumdiga-ga on 19 Apr 2002 08:25 PDT
Monitor Power Management Calculator is Helpful in Computing the Cost Savings on 
the basis of certain criteria such as  “Number of Computers”, “Usage Per 
Day “, “Usage Per Week “, “Percent Turned of Nights & Weekend “ etc…

Monitor Power Management Calculator is available on the EPA (United States 
Environmental Protection Agency) Website.

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