The energy regulator wants power firms to do more to combat electricity theft, a third of which is stolen each year to power cannabis farms.
Ofgem has published proposals to combat a problem that it says costs customers £200m a year.
Ofgem said new rules should force suppliers to detect and investigate problems, or risk a fine.
The regulator estimates that there are up to 25,000 cases of electricity theft each year.
Under the proposals, suppliers are being asked to set up a national theft-risk assessment service to help them target premises where there are strong suspicions that electricity is being stolen, most commonly through tampering with meters.
Ofgem says theft costs paying electricity customers the equivalent of £7 each a year.