The uptake of rooftop solar panels has been so rapid in Perth that it could soon leave the grid dangerously exposed to a "system collapse", an electricity expert has warned.
Ken Brown, who ran Western Power's network for 20 years until 2012, said the South West electricity grid had been able to handle demand for solar panels safely until now but this could not go on for ever.
Mr Brown noted that unlike power stations, output from solar or photovoltaic panels could not be reduced or switched off. He said this had not been a problem while the number of solar panels and their combined capacity across the grid were manageable.
There are about 136,000 Perth and South West electricity customers with solar panels that have a combined capacity of about 350MW - the equivalent of a base-load coal or gas-fired power plant.
Amid forecasts by State-owned electricity provider Synergy the capacity could rocket to as much as 1500MW by 2020, Mr Brown said solar could soon pose a security risk to the grid.
Giving the example of a warm weekend day - when businesses were often closed and electricity demand was low - he said 1500MW of solar would represent almost two-thirds of supply.
"You don't want to put 1500MW of (solar panels) on and then turn around and say, 'I can't run the power system'," Mr Brown said. "Because a nice, warm Sunday in 10 years time - the whole power system might only be 2500MW, so you've got nearly two-thirds of your system on (solar).
"This is a very insecure way to operate the power system, because if clouds come over the Perth metro area it will significantly reduce the output of the PVs, which could lead to a system collapse in the worst case."
Sustainable Energy Association boss Kirsten Rose said Mr Brown's warning presupposed Western Power had no control over the amount of solar installed on the grid.
She said it was also important to remember the grid's ability to handle solar would increase as technology improved. "If anything they (Western Power) are hyper-conservative about letting (solar) on because of the risks they believe it represents to the grid," Ms Rose said.
'This is a very insecure way to operate the power system.'"Former Western Power network manager *Ken Brown *