I've been doing some research into pre-built electric all-in-one brewing systems (Robobrew, Grainfather, etc) vs DIY electric systems. The prevailing sentiment is that a DIY 110v 1500 watt system is not enough to achieve a full rolling boil, however the descriptions for the Robobrew and Grainfather systems are claiming that a full rolling boil can be achieved with this wattage. I've seen many reviews backing this up as well.
What are the fundamental differences between a pre-built system and what DIYers are doing? Are there links to any plans or reviews of DIY electric systems that achieve similar results and have similar specs to the pre-built systems?