National grid officials say 2,300 of the illegal marijuana plantations busted last year were being run on stolen electricity.

In total, the growers stole 114 million kilowatt hours of electricity, but the real total is likely to be in the region of one billion kWh, Netbeheer Nederland said. That, the organisation calculates, is enough electricity to power all the households in Rotterdam for one year.

Stealing electricity is not only illegal but dangerous and can cause short-circuits and fire, experts say. This, says Netbeheer Nederland, is particularly worrying because so many plantations are found in apartments and private homes.