The owner of the Hazelwood brown coal generator has defended its decision to charge a higher fixed tariff to households with rooftop solar, saying extra slugs on solar households were commonplace.

Trevor Rowe, a spokesman for GDF Suez, which owns Hazelwood and other generators, and the retail arm Simply Energy, says other electricity retailers penalised solar households with reduced discounts or different tariff structures.

The Simply Energy standard rate, which charges $51 a year more to solar households in the fixed component of its bill – was simply more transparent.

Rowe’s comments came as the Victorian Labor Party also reacted to revelations in RenewEconomy on Monday that solar households were being slugged with extra charges, and its implicit support by the Napthine state government.

“Ordinary families shouldn’t be punished for saving energy and saving money on their household bills, Labor’s energy spokeswoman Lily D’Ambrosio said in an emailed statement.

“With car rego and council rates increasing, Victorian families are already finding it harder to make ends meet. Under the Liberals, our environment goes backwards and our power bills go upwards.”

Simply Energy has some 500,000 customers in Victoria and other states, but could not provide details on how many had rooftop solar.

Solar is emerging as a potential electoral issue, given the kick-back against the WA government when it tried to introduce retrospective changes to its solar feed-in tariffs last year. It reversed the decision.

Simply Energy’s Rowe said the company was “not discriminating” against solar households with the differentiated tariffs.

“Certainly not,” he told RenewEconomy. “There are different costs involved with solar and different companies deal with it in different ways.

“It is the total package that is important, not just the fixed charge. Customers are fully aware of the higher supply charge when they sign up.”

His comments came as customers of other retailers complained about “reduced discount” and higher tariffs imposed on solar households.

One customer, from Red Energy, the retail offshoot of Snowy Hydro, complained in a forum that he had been because he had installed a solar system, his contracted rate would change from 23.35 c/kW to 32.18 c/kW peak and 17.28 c for off peak.

Such complaints have become common. RenewEconomy will be pursuing the matter and would like to hear from others who have noticed similar moves. Please email at editor (at) reneweconomy.com.au or post a comment here.