Climate tech doesn't have to be crazy futuristic ML models or whatever in order to be useful. For instance, I love the Purple Air air quality sensors, which cr

Climate tech doesn't have to be crazy futuristic ML models or whatever in order to be useful. For instance, I love the Purple Air air quality sensors, which crowdsource data and use a simple existing technology. (See https://map.purpleair.com/ https://map.purpleair.com/). This example may not be "revolutionary" enough for YCombinator, but I'm a fan. Personally, I'd like to see a company that focuses on solar hot water heating. Water heating is usually about 1/3 of a home's energy usage. In several countries, especially in the middle east and in Africa, standalone solar hot water systems are the most common way water is heated. But in the US, solar hot water is nearly non-existent. I'm not talking whole-house solar panels, but rather a small system that you can buy for $~4-5k. There's an opportunity lurking there somewhere.