Mainly data collection (previous lead dev at solar forecasting startup). All the web UIs to view usage are also collecting useful information that can be used in forecasting models. One of the researches I worked with wrote some papers on using distributed home solar output measurements to assist with generating higher resolution irradiance forecasts and estimated actuals/observations. You have to do a lot of data cleaning to get this reliable though. Anyway, this data from memory was bought/sold for various research/commercial weather modeling.