CRT vs LCD monitor
There are bad LCD's and good CRT's, so verification through the specs in the EU ENERGY STAR database is important. Still...
LCD monitors use on average 50 to 70% less energy in on-mode than conventional CRT (Cathode Ray Tube) monitors. A recent LBNL study on new monitors and personal computers reports that in their sample 15" LCD monitors consume 30% as much power when on as 15" CRTs, and 17" LCDs consume 51% as much power when on as 17" CRTs. This advantage tends to get smaller as LCD screens become bigger.
That said, the actual size of a monitor may not be what it seems: A nominally 16" LCD screen will have approximately the same surface area as a nominally 17" CRT.
If the off-modes (when the power switch is on the low side of the power supply) of CRTs and LCDs are compared, off power consumption is similar: around 2W. (max 15 kWh/year. See also power supplies). However, many CRTs have the advantage of a hard-off switch on the high side of the power supply, whereas most LCD's have an external power supply.
In the sleep-mode, the LBNL study found similar energy consumption values of approximately 2W for both LCD and CRT.
All in all, at 8 working hours a day, the energy saving of choosing an LCD over an equal size CRT could typically be well over 100 kWh/year.
Depending on your local electricity rate, this may entail a saving of up to € 20/year and up to € 100 on the product life. Together with other advantages saving space, displaying a calmer image and possibly saving on air-conditioning the LCD monitor may therefore be not only the best environmental option, but also economical in terms of cost-of-ownership for office-workers or power users at home.
Especially now that some of the past snags of LCD technology have been eliminated there is hardly an area where LCD would be excluded: the latest generation of LCD monitors can now match and often beat CRT specs in terms of luminance, viewing angle, ailing, brightness, etc..
Courtesy of the French Energy Agency ADEME, Future Electronics project.
Power Levels in New Monitors and Personal Computers, LBNL-48581, July 2002. Download at : http://enduse.lbl.gov/Info/LBNL-48581.pdf