The Economist has a well written article on the issues with Energy Conservation. It gives a good perspective from the holistic view of the potential energy savings from conservation and dives into details of implementing programs and energy saving appliances.

Anyone who is thinking of Green Data Center projects should read this article to get a good perspective on the issues on saving energy.

Here are a few highlights from the article.

Energy efficiency
The elusive negawatt
May 8th 2008
From The Economist print edition
If energy conservation both saves money and is good for the planet, why don't people do more of it?

IN WONKISH circles, energy efficiency used to be known as “the fifth fuel”: it can help to satisfy growing demand for energy just as surely as coal, gas, oil or uranium can. But in these environmentally conscious times it has been climbing the rankings. Whereas the burning of fossil fuels releases greenhouse gases, which contribute to global warming, and nuclear plants generate life-threatening waste, the only by-product of energy efficiency is wealth, in the form of lower fuel bills and less spending on power stations, pipelines and so forth. No wonder that wonks now tend to prefer “negawatts” to megawatts as the best method of slaking the world's growing thirst for energy.
The problem, analysts explain, is a series of distortions and market failures that discourage investment in efficiency. Often, consumers are poorly informed about the savings on offer. Even when they can do the sums, the transaction costs are high: it is a time-consuming chore for someone to identify the best energy-saving equipment, buy it and get it installed. It does not help that the potential savings, although huge when added up across the world, usually amount to only a small share of the budgets of individual firms and households. Despite recent price increases, spending on energy still accounts for a smaller share of the global economy than it did a few decades ago.
For all these reasons, homeowners, as Lord Stern pointed out in his climate-change report, tend to demand exorbitant rates of return on investments in energy efficiency—of around 30%. They generally want new boilers or extra insulation to pay for themselves within two or three years, says Mark Hopkins, of the United Nations Foundation, an NGO. Businesses are not quite so demanding, he says, but they still tend to put greater emphasis on increasing revenues than on cutting costs.
Similar stories crop up in the markets for new homes and offices, appliances and vehicles. Builders are not the ones who end up paying the utility bills, so have little reason to add to the construction costs—and hence the price of a home or office—by incorporating energy-saving features. The makers of appliances and cars also know that not all consumers and drivers will think as carefully about running costs as about the purchase price. By the same token, landlords have scant incentive to invest in energy efficiency on their tenants' behalf. And power companies are usually keen to encourage their customers to consume as much power as possible.

And, as Microsoft's Christian Belady has pointed out increasing efficiency does not necessarily decrease demand. The Economist reinforces the idea of the "rebound effect."

However, no matter what methods governments adopt to encourage energy efficiency, the results may not be as impressive as they imagine. The culprit is something called the “rebound effect”. Falling demand for electricity or fuel brought on by an efficiency drive should lead to lower prices. But cheaper energy, in turn, is likely to prompt greater consumption, undermining at least some of the original benefits. What is more, consumers with lower electricity or fuel bills often put the money they have saved to some other use, such as going on holiday or buying an appliance, which is likely to involve the consumption of fuel and power.
Economists disagree about the size of the rebound effect, which is hard to measure. The British government commissioned two studies of the effect, from two different universities. The first found that it cancelled out roughly 26% of the gains from energy-efficiency schemes; the other put the figure at 37%. Either way, negawatts are worth pursuing. But they are unlikely to satisfy the world's thirst for energy to the extent their advocates assume.

Another good example of the rebound effect is in virtualization projects.