How do you estimate market size for residential solar in emerging markets?

For Southeast Asia specifically, I'd start with a top-down approach using electrification rates and avg household income data from World Bank + IRENA's country profiles, then layer in grid reliability stats since that's a huge adoption driver in markets like Philippines and Indonesia. GOGLA also has solid off-grid solar market data that's free to access. From there, bottom-up validation through a small survey of 200-300 households in your target income tier will tell you a lot about willingness to pay vs. actual ability to finance.