Data collected by Green Energy Trading shows residential installations accounted for 18.4 megawatts of capacity, up from 9 megawatts in 2017. The 104.4 per cent year-on-year growth rate was easily the biggest in Australia.

Commercial installations also more than doubled in the ACT with 4.4 megawatts of capacity installed in 2018, up 109.5 per cent on the 2.1 megawatts added the previous year.

Green Energy Trading director Tristan Edis said 3333 solar panel systems were registered for the small-scale technology certificates rebate in the ACT last year, up from 1666 in 2017.

"It's interesting that the ACT has grown so much because it's more spectacular than what we've seen in other states and territories," he said.

Mr Edis said it was likely that Canberra customers were taking note of falling panel prices as they looked for ways to reduce their increasingly steep power bills.

The territory's Independent Competition and Regulatory Commission allowed electricity providers to increase prices by 14.29 per cent this financial year, following a 17 per cent increase the previous fiscal year.

Mr Edis said those price hikes were largely a result of rising wholesale prices, while previous increases had been driven by network and retail charges, which had hit other jurisdictions harder than the ACT.

"ACT consumers would have seen a more substantial increase in their power bills in the last two years," he said.

"That would probably be a factor in more people looking at things like solar."

Cook resident Bob Hay had rooftop solar panels installed last year as part of the ACT government's $25 million Next Generation Energy Storage Program.

The program is subsidising the rollout of about 36 megawatts of "smart" battery storage in up to 5000 Canberra homes and businesses, as part of the ACT government's drive to make Canberra fully powered by renewable energy by 2020.

More than 1000 battery storage systems have been supported so far.

Mr Hay said the heat in summer "knocked him for six" and he used to feel guilty for putting the air-conditioning on because of the cost it added to his bills.

The 82-year-old said he used to get quarterly electricity bills of between $200 and $300, but the first one he received after getting solar panels was just $28.

"One of the reasons was just [to] save the planet, but what it also boils down to is that it's cheaper and I'm more comfortable," he said.

As part of the Next Generation Energy Storage Program, homes and businesses that install a battery connected to a solar system receive support of up to $825 for each kilowatt of sustained peak output.

Climate Change and Sustainability Minister Shane Rattenbury said this was worth about $4000 to the average household.

“It’s no surprise that Canberrans are taking up clean, green renewable energy options in droves," Mr Rattenbury said.

"Renewable energy is the way of the future, delivering clean, reliable and more affordable energy for Canberrans while helping to protect our planet."

The average ACT resident's annual electrical bill is set to rise by 5 per cent between June 2019 and June 2021, according to the Australian Energy Market Commission. The average annual bill will rise from $1717 this financial year to $1804 in 2020-21.

Mr Rattenbury has said despite short-term price increases, electricity prices should stabilise through the 2020s, with contracts for renewable energy over the next 20 years to deliver long-term benefits for Canberra.

While Canberrans are installing solar panels at a rapid rate, the overall proportion of homes with rooftop solar is lagging behind the national average.

Analysis by solar energy consultancy SunWiz shows 22,120 ACT homes – 15 per cent of the total – have rooftop solar.

Across the country, 20.3 per cent of homes have solar panels, with South Australia leading the way at 31 per cent.