Spot solar umbrella when?
The 400 W average power is taken from the official specs of 605 Wh battery capacity and 90 min average runtime. The STC wattage of the solar panels is just from rooftop solar panels everyone can buy. There are more powerful panels if you can spend more money. It needs to be on a self balancing stick.

A big enough solar umbrella would allow Spot to patrol all day, also on moon or mars. It already makes sense on earth as 90 min is not a long battery life.