White rooftops are more efficient than dark coloured rooftops. While in winter a dark roof heats up in the sun and helps reduce your heating bill - the same rooftop in summer makes your house even hotter, and your air conditioning has to work harder. In most places, the summertime penalty is greater than the wintertime gain. Turning all the world's roofs white would eliminate as much greenhouse gas emissions in 20 years as the whole world produces in a year.

Recessed downlights are like having holes in your ceiling. They let a lot of heat escape in winter. But now you can buy isolators that sit over the fitting above the ceiling and reduce the air flow and the fire hazard.

With a solar hot water system, you could get between 50 and 90 per cent of your hot water for free.

By 2021 Australians could save more than $600 million through reduced energy and water bills by choosing more energy efficient products.

Boiling water with an electric kettle or gas cooker generates about half as much greenhouse gas as a microwave oven or an electric stove. You can save even more energy by only boiling as much water as you need.