My parents live in a part of India where summer temperatures routinely hit 45C (113F). Because electricity is expensive and my parents&#x27; house is quite large, they couldn&#x27;t afford to run air-conditioning for more than 8-10 hours a day - usually at night.<p>Whenever I would go home, the heat would completely wreck my productivity. I would have to sequester myself in the coolest room in the house, then judiciously use the air conditioning to maintain some semblance of sanity.<p>Then my dad got fed up and took advantage of a government subsidy to buy solar panels.<p>It was expensive initially, but now we essentially have free power. We&#x27;ll break even in terms of costs within 4 years.<p>We now run air conditioning when we want, wherever we want.<p>The increase in productivity is <i>massive</i>. I no longer have to deal with heat when I go home.<p>Now imagine this happening for billions of people living in tropical climates.<p>It&#x27;s going to change the contour of the world