I use to wash my EPDM roof with a long handle brush, bucket of soap, garden hose and it would take me 4-5 hours with brakes.
Two years ago I got a 1350 PSI pressure washer. Now I am only up there about a hour doing the roof, AC covers, 2 Satellite dishes, Vent covers etc.
And it gets that winter green mold off everything way better then I did using a brush.
The sides still like a brush & pad to get the dirt off. But I use the PW to put the soap on & rinse the dirt off.
99 Discovery 34Q ISB
2014 MKS AWD EcoBoost Toad
Fulltime Since "99"