In the bad old days, energy plans often had fixed duration, and there would often be fees for early contract exit. Today there is regulation in pace that limits retailers ability to charge exit fees, so much so that none of them even try to charge exit fees any more.
​
Retailers do list 'disconnection' and 'reconnection' fees in their standard schedule of fees that you'll find in their contracts.

These fees apply only to physical disconnection or reconnection of power from the property, which will only be required if you're setting up a brand-new energy supply at newly built premises, or if the existing premises are scheduled for demolition or are being left empty for a long period of time.

Retailers do not actually supply your energy—they only supply your bills—so when you're switching retailers at the same address, your power will not be disconnected at all. There is no disconnect or reconnect required, and there will be no disconnection or reconnection fee whatsoever.
​
So you can use Bill Hero with confidence that your savings will not be eroded through exit fees.