This could discourage interconnectedness of the grid. If player A has to worry about Teammate B risking their collective energy by poorly protecting his energy, then the grid linkage may be *bad*. Right now, the players think "always link". I'm not sure about "linking is now a bad thing".
More likely would be a unit that simply steals 100% of the energy from all energy buildings in radius around it, rather than leeching energy from things deeper within the grid. But this would have no impact on pylons, and would steal only a pittance for all the risk if you got it next to some Solars or Winds.