Thanks!

If I’ve got a 100W load (12V DC, no inverters just its own power regulator, this is an estimate but ballpark) and want to charge a battery for night running as long as possible, would a single 250W panel do or do? There’s obviously multiple reasons it needs to be bigger than the nominal wattage of the load

inefficiency (panel inefficiency, actual sun conditions, battery charger/regulator inefficiency)

battery charging during the day

Are there calculators to estimate this sort of thing?