What a wonderful design!
I wonder why the motor driver needs 45W of power resistors and I'd love to know where he gets a 3KW shower from, mine is 8.5KW and UK ones often go as high as 10KW. The inverter unit also looks remarkably similar to one I have except for the brand name. Strange that mine produces modified sine at a maximum of 300W (and that is just about all it can manage before shutting down) yet his is 2000W continuous, 4000W peak.
There is another video on the same source that explain how to tune electricity by adding resistors across it. Probably works on a similar principle.
Brian. (who is also being sarcastic!)