Having an energy efficient household doesn't mean you have to line your roof with solar panels. There are a lot of simpler ways to cut down on how much power your home needs to keep running — such as these KSD tri-pane solar windows thought up by Eco-Logical Innovations. KSD windows help you regulate the amount of heat that gets through them thanks to a green pane of glass and a clever swiveling design.
Turn the window so the green pane is on the outside of the other two and it'll reflect heat, which means you won't have to kill your air conditioner trying to keep cool. When it's cold, just flip the window around and keep the heat in so your place is nice and toasty. The panes also provide improved noise dampening over normal windows, and have a pane of safety glass for security.
KSD windows have been on sale for a few years in Germany and are now making an appearance in the States. No word on pricing yet, but the real cost of an energy-saving measure like this isn't how much it takes out of your wallet, but how much it shaves off your bills.