Two route to answer here.

The first is general green technology in general. Sustainability initiatives require reducing the energy intensity of industrial and consumer applications. Computing is part of that. Greener computing reduces the energy intensity of economic activities improving the energy intensity of economies (i.e. increasing the GDP per unit of energy used.) This has the same general impact as environmental sustainability issues in general.

Second is in terms of operations cost. For large data center or supercomputers the energy intensity is a big concern. Let's take round order of magnitude numbers. A top supercomputer today costs on the order of 100M$. (or maybe a little less, I overestimate a bit to make THIS calculation conservative.) The power required to run the machine is on the order to 10 MW. If the machine has a useful life of say 3 years. This is 26,000 hours. Now if you are lucky you can buy energy for $0.1/kWhr. That means your machine costs $1,000 per hour to run just for the electricity. Over the life of the machine you will spend 26M$ just for electricity! This has two BIG effects. First the total cost of ownership of supercomputers (or datacenters) is greatly affected by the energy use. Second, because of the high cost of energy, the lifetime of machines are shorter. Machines still work after 3 years but the cost to operate them are too high in comparison to value when the newer machines are available in three years and the old ones are too expensive to operate. Let me restate this in bold: supercomputers are turned off not because they end their useful life but because they use too much energy in relation to other options.

Green computing means less energy per computation which allows you to buy more computer per budget dollar on a lifetime cost basis and allows you to economically run the machine longer.

In fact it is so important that the logic runs in reverse. For example, early scoping studies for the US exascale effort REQUIRED the power of an exaflop machine to be less than 20 MW. Straight scaling from the petaflop era would have given a machine with a power well above 100 MW. So from the start, the exaflop project REQUIRED planners to plan for an increase in computing efficiency of an order of magnitude. To state it another way, green computing is a prerequisite to play the supercomputing game today. You must be this green to rider this ride.

Note: this discussion is not quite the same as the discussion of the "power wall" and the failing of Dennard scaling in HPC. There the issue is the inability to dissipate heat on a chip. However, the two problems scale similarly and the solution to one helps the solution to the other.

Thanks dear John W Cobb worthy insight.

The advantages of green computing can be seen on a large scale as well as a small scale. You can make use of green computing in the entire organization or just for a single workstation.

Unfortunately many businesses today are going for green computing because of the large initial costs involved, however they don’t understand how much savings they can make in the long run. Eventually the savings from green computing will outnumber the costs.

Cloud computing is the latest trend in the field of green computing. Cloud computing does away with the hardware servers and uses virtual servers also called servers in the cloud. Hence cloud computing will help the companies to get rid of their bulky servers that consume a lot of energy. Cloud computing will soon be used in areas such as networking, data storage and running operating systems. This way, businesses will save a lot of time and energy by switching to cloud computing architecture.

Green computing can also be used in other areas such as saving paper by sending email. You can even implement other practices such as printing your content in smaller fonts. Teleconferences and telecommuting can indirectly save a lot of carbon dioxide emissions in the environment.