Disadvantages

Green computing could actually be quite costly.

Given that there has been a green process that the computer will have gone through in order to make the computer in the first place; there will usually be some kind of added cost when the computer has been finished. Green computing takes a lot of new technology, and hence, you may find that you will have to pay a premium price for your new green computer.

A perfect example is that the greenest modern computers today are Mac books and Mac book Pros. These computers are hardly inexpensive - they're actually some of the most expensive computers in the market.

Some computers that are green may be considerably underpowered. 

Some people may need incredibly power-consuming and powerful computers to deal with the tasks that they need them to do. This is another disadvantage that many people who have high-powered computers believe to have with green computers. 

Another issue would be that powerful and green computers are more expensive. For instance, Apple's powerful range of computers, including their iMacs, is incredibly green but is also incredibly expensive.

Rapid technology change, low initial cost, and with planned obsolescence has resulted in a fast-growing surplus of unused hardware around the globe. Dave Kruch, CEO of Cash For Laptops, regards electronic waste as a "rapidly expanding" issue. 

Technical solutions are available, but in most cases a legal framework, a collection system, logistics, and other services need to be implemented before a technical solution can be applied.