Energy efficiency is vital to stabilizing climate change NOW with today's technologies. It alone will not be enough to solve the problem, however if combined with other practices such as nuclear energy, renewable/bio-storage, fuel based strategies, and other energy efficiency methods then we can hope to prevent a doubling of C02 (see first two links for more info).
Our homes make up a significant portion of energy consumption (seen in the third link). That is why you may have heard people state, "there is NO SILVER BULLET to climate change" and why many are in favor of a cap and trade policy on carbon emissions.
This doubling of carbon is bad because it is predicted to lead to significant global warming effects. However with the amount of money currently being invested in green practices and energy, we can be optimistic on the future of our planet. The fourth link is an example of an awesome green building, which is a home that "is environmentally responsible and resource-efficient throughout a building's life-cycle: from siting to design, construction, operation, maintenance, renovation, and demolition(wiki)."
Hope this was helpful!
Essentially because as far as a government's concerned, getting you as an individual to cut down on your energy usage is a lot easier than doing something about the various industrial consortiums who have much more political clout than you. Not that you should mind ending up paying less in the long run for the cost of your maintenance, but you should know that the residential sector is dwarfed by the industrial sector & creators of electricity who mostly provide electricity who mostly provide energy to the industrial. And it's further complicated by things like putting scrubbers on a smokestack so that you're emitting less pollutants to the environment at large means that your coal plant becomes less efficient meaning in the end that the cost goes up. Myself, I like clean air & water, but the energy producers are trying to extract every cent they don't have to pay any more for, so they put their money into paying lobbyists to make sure that their profit margins don't become regulated & enforcement of anything like that becomes negligible.
There is no free lunch on the planet, everything comes with a cost & although most people are willing to pay more for a cleaner planet, none of them seem to be in the energy business.
Sorry about the rant, but most everything you do affects something else & that's pretty simple & something to think about when using a cell phone as more people at this point have died in The Republic of Congo's civil war than in W.W.2 to bring you an ore that makes electric capacitors as cheaply as possible.
It's to keep us warm through winter and keep energy bills down.
Not sure exactly but I know it has something to do with your carbon footprint.
How does this have an impact on the environment?
