I think that your recollection is incomplete or garbled. Modern solar panels are about 20% efficient. They can generate about 200 watts per square meter in midd

I think that your recollection is incomplete or garbled. Modern solar panels are about 20% efficient. They can generate about 200 watts per square meter in midday sun with clear skies. 2000 to 3000 watts of panels would be about 10-15 square meters (107-161 square feet). Do these vans actually have roofs that large, completely covered with panels? You might expect roof top panels with sub-optimal orientation to generate about 12.5% of their peak rating when averaged over a year. That would be 375 watts, annualized, from a system with a peak capacity of 3000 watts. There is no van-portable battery system currently on the market that can store 375 * 24 * 23 = 207,000 watt-hours. (For comparison, the Tesla Model S battery stores 100,000 watt-hours.) My guess is that you are not correctly recalling how much solar capacity these vans have installed. When I Google for van life solar I get guides and kits referencing much less power. For example, this guide: https://www.genericvan.life/2018/04/30/complete-vanlife-solar-system-for-under-1000/ https://www.genericvan.life/2018/04/30/complete-vanlife-sola... uses a single 150 watt panel. Based on the photo the article includes, I don't think that the van rooftop has room for more than 3 panels of this type.