The generous scheme pays people as much as 50 cents a kilowatt hour for the energy they feed into the grid from the solar panels on their roofs, and such was the clamour to join when it began in early 2009 that the scheme was closed to new customers in 2011 and already looking to overrun its 30 megawatts capacity.

But if people had a contract signed for a rooftop installation when it closed they are still entitled to the premium feed-in tariff for 20 years from the date they hook up to the grid. More than 5000 have connected since the scheme closed.

In all, more than 10,000 households are signed up to the premium tariff. In the past year, they were paid $16 million for the electricity they produced, or an average of about $1600 each.

Environment Minister Simon Corbell has now set a deadline for connecting rooftop installations under the scheme of December 2016.

He has also closed a loophole in rooftop solar that would allow people to store power and sell it back at the premium rate. The loophole has not been exploited, according to Mr Corbell's spokesman, but storage technology is becoming more widespread.

The move "explicitly prohibits export of electricity that has been sourced from a non-renewable source such as the electricity grid, to claim [feed-in tariff] entitlements," he said.

"While this is not an issue currently, this amendment is targeted at preventing exploitation of [feed-in tariff] entitlements for non-renewable electricity in the future. Rapid advances in storage technologies are leading to lower costs of batteries which is likely to result in greater uptake by households and businesses."

Mr Corbell also wound back reporting requirements so instead of a monthly report on the scheme, he is obliged to report once a year.

The changes were introduced in May and passed with little fanfare during the first week of June, when attention was focused on the budget.

ActewAGL said last year the average Canberra installation was about 2.5kW, with a 3kW installation covering the energy needs for a typical house. Larger than that and householders are earning money on the deal.

It now pays just 7.5 cents a kilowatt hour for rooftop solar for people not in the premium scheme.

Mr Corbell's spokesman said there were only a small number of customers yet to be connected to the premium scheme - about 404 kilowatts in small-scale solar and 7 megawatts in medium-scale capacity, which would bring the total capacity to about 33 megawatts.

Since the scheme was closed, households had added about 18.8 megawatts of rooftop solar without the support of the premium tariff, bringing the total in small-scale solar to 44.8 megawatts, including households on the premium tariff and those who were not.