Planned electricity interruptions will affect a further six suburbs in the capital on Friday, but a spokesman for ActewAGL said no information was being released regarding which areas would be affected.

Heatwave conditions are expected to remain throughout this time, leaving some Canberra residents without airconditioning in the predicted 40-degree heat.

The maintenance work follows five outages across the capital on Wednesday, which sparked six complaints and a further 21 inquiries. ACT Opposition Leader Jeremy Hanson said his office had received calls from locals regarding the outages.

Mr Hanson said ActewAGL should ''practise some commonsense'', particularly given the heatwave warning issued by ACT chief health officer Paul Kelly on Wednesday.

''I'd be calling on ActewAGL to not shut down power on extreme days,'' Mr Hanson said. ''I think the government's aware of the situation. I certainly hope the government would echo my sentiments.''

Comment was sought from Acting Chief Minister Andrew Barr.

An ActewAGL spokesman said efforts were being undertaken to minimise the impact on customers, including some crews starting work at 5.30am.

''It is essential that we continue with our maintenance program to help prevent bigger problems, longer outages that affect more people, which could result in unsafe conditions,'' he said.

''Our essential maintenance program is also an important part of our bushfire mitigation strategy.''

He said all customers could have received written notice of the outages at least four business days before work was undertaken, adding that the company would investigate any claims that customers were not notified. Temperatures are expected to peak at 40 degrees on Thursday, before dropping slightly to 39 degrees throughout Friday and Saturday.

Electricity usage has been increasing during the heat, rising from 535MW at 6pm on Tuesday to 575MW at 4pm on Wednesday.

Last summer's peak of 700 MW occurred at 4.45pm on Friday, January 18, 2013, when it was 42 degrees.