We spend a lot of energy (and money!) on heating up our houses in winter, and cooling them down in summer. In most cases, the electricity used for this purpose comes from an external source. How can nanotechnology be used to improve on this situation? One way is to reduce the need of heating and cooling. While the walls of most modern houses are properly isolated, so that there is little heat transfer through them, the windows are still great sinners. There have of course been improvements here as well, but a lot of heat is still lost through our windows due to radiation. What if we could prevent heat from escaping our room in winter, or preventing it entrance in summer? A company called Nanoholdings have developed a film, made up of carbon nanotubes, that by applying a voltage can change how much light and heat it lets through the window. This could also potentially be used to harvest energy. Nanotechnology can also be used to drastically improve the efficiency of solar cells. The average efficiency of today’s solar cells is around 15%. That is, it only transforms 15% of the solar energy that hits it into electric energy. The theoretical max efficiency is also under 50% for today’s technology. But if we were to infuse the material with nanoparticles and nanowires, and effectively increase the amount of different wavelengths of light that can be transformed, we can gain a max theoretical efficiency of up to 90%. That means we can almost double energy production across the same area!