Experts say powerlines may be limiting the savings Australians can make from solar.

More than 2 million Australian households have a rooftop solar system.

But the broad uptake of rooftop solar has been blamed for destabilising the grid by increasing voltages on nearby electricity lines.

A University of New South Wales (UNSW) study has now found that these line voltages are already close to, and sometimes over the allowable limit, so rooftop solar has little impact.

If powerline voltage is too low, the power may cut out, but if it is too high, energy is wasted, power bills increase, and some appliances may burn out.

UNSW has crunched data from over 12,000 solar households, analysing the voltage before any extra solar power could affect readings.

The researchers found 95 per cent of readings were higher than the nominal voltage on the grid of 230 volts.

With voltage levels near or even above 253 volts in some cases, there is no room for households wanting to feed even tiny amounts of solar energy back into the grid.

The study was commissioned by the Energy Security Board (ESB), which said the finding show a “material level of technical non-compliance” by the networks.

Energy Networks Australia (ENA) – a lobby for ‘poles and wires’ companies – says that network companies themselves are working with very limited information about voltages near people's homes.

“We need more information. This is the challenge — knowing what is going on in the grid,” Andrew Dillon, chief executive of ENA, said.

Mr Dillon said network operators are looking for solutions to high voltages that would not drive up power bills.

“There are simple measures we can take to start to remedy this and they are all underway pretty much everywhere,” he said.

Renewable energy advocates agree that more information is needed about background voltage levels set by networks.

Regulators in Queensland, New South Wales, the ACT, Victoria, South Australia and Tasmania do not appear to have any examples of when, or if, action had been taken on voltage issues.