Five months of industrial action by workers at poles and wires company Endeavour Energy has delayed the construction of 1600 homes and a slew of warehouses owned by ASX-listed property giants, adding millions of dollars in extra costs.

As part of an ambitious push for a 24 per cent pay rise, about 750 Electrical Trades Union (ETU) members at the distribution company, part-owned by the NSW government, have refused to show up at appointments to switch off powerlines on construction sites since February.