Can't they upgrade it?
This sounds like an excuse.
If you need more electric capacity, you pay the local electricity distribution network to install bigger wires to your property, and as part of that they'll upgrade substations and interconnect wires as needed - and you pay for all this work.
Of course, this may be _very_ expensive, but it's doable.
But "it's impossible because it would melt the substation" is a MUCH better excuse than "we don't want to pay for a bigger electrical connection".