Household electricity and gas usage has jumped by about 15 per cent because of people working at home during the day, industry experts claim. Businesses are using about 12 per cent less.

In April in the ACT, at the height of the lockdown, households were using double the amount of electricity in the early afternoon compared with the amount they used before the lockdown when working in an office was the norm.

Now the bills are coming in.

Fuel bills for an "average" ACT household are estimated to have risen by between $176 to $220 per year for electricity and by between $149 to $212 for gas since the virus crisis changed working habits, according to the WATTever organisation which compares energy prices.

Typical annual electricity bills in the ACT range from $1530 to $1822 and rise to a range of between $1706 to $2042 because of the switch to home working.

Evoenergy, the main Canberra supplier, confirmed there was "an increase in electricity demand from residential customers in April and May with a peak at midday".

Industry experts said the shift from office work to home work meant a shift in who was paying the heating bill.

"There is a potential for 'bill shock'," said Gavin Dufty, who researches the energy market for the St Vincent de Paul Society.

That "bill shock" will be greater for people who get quarterly bills, he said. The jump in the bill would look greater than if it arrived in smaller doses every month.

The latest quarter to be billed was April, May and June when the virus hit and office workers were sent home.

The most accurate estimate of how home fuel consumption had risen comes from Victoria because Victorians are on smart-metres - but experts said the pattern would be repeated across the states and territories.

The ACT was likely to see an even bigger rise in household electricity consumption because office work was a bigger part of its economy and because of the coldness of the Canberra winter.

The ACT Council of Social Service said people who moved from office to home work were not always well-paid. It also affected lower-income workers.

ACTCOSS chief executive Emma Campbell feared some people might not heat their homes enough as bills climbed.

The extra cost of working from home varied by household - if two people worked from home in separate rooms, the cost would be higher.

The big extra cost of working from home so far was heating but there were other costs, consumer protection group Canstar Blue revealed.

Much depended on tariffs and suppliers but it reckoned, for example, for an "average" family, the extra fortnightly cost of using the home computer was:

Other costs like car use may have fallen because people had moved from the office to the home for work.

But higher heating costs (and cooling costs if the crisis continued into the summer) were unavoidable, said David Hiley, the founder of WATTever.

"It's something we have to accept," he said.

"The thing is to shop around."