A Canberra woman says her family did just that when the company, Upside, sold her grandmother's Farrer home after the 98-year-old's death earlier this year.

But an industry expert has warned people to consider that using a company that charges fixed fees may mean agents have less incentive to achieve the best price.

Upside chief executive Adam Rigby said most traditional real estate agents charged commissions ranging from 2 to 3 per cent of the total sale price.

That meant that if a home sold for $740,000, traditional agents would generally receive a commission between $14,800 and $22,200.

Mr Rigby said his company only charged a flat fee of $8900 for a private treaty sale, or $9700 for an auction.

Chifley woman Jenny McAlister said Upside sold her late grandmother's Farrer home for $740,000, meaning her family saved several thousand dollars in fees.

That figure is just short of Canberra's median house price, which is $741,947 according to the Domain Quarterly House Price Report released on Thursday.

Ms McAlister said the family was initially apprehensive, but the fixed-fees approach had worked well in their case and the house was sold about three months after being listed.

"I was dubious at first, thinking, 'What are they going to do that's different? How are they going to make money if they're not taking more advantage of the sale price? Will they push for the best price for us?'" she said.

"But the sale went through quickly and there was really good communication.

"I didn't think there was any less coverage than we would have got with a traditional agent and we got a price that we were obviously happy with because we sold [the house].

"During what was a sad and stressful time for the family, it was good to know there was a bit of certainty."

Real Estate Institute of the ACT director Craig Bright said a fixed-fee approach was "not right or wrong" in any given case, but he warned people to consider the potential pitfalls.

"If you look at agency agreements, which have been around for 150 years, it's always been based on a percentage, which is obviously an encouragement for agents because the better they do for their clients, they better they do for themselves," Mr Bright said.

"To me, [a fixed-fee model] is like saying to a lawyer, 'I want you to run this case for me, but I'm going to cap your fee no matter how many hours you work'.

"If you're on a capped fee, does that become a disincentive [to the agent] the longer it's on the market? It could put the seller under pressure, in terms of what they are prepared to accept."

But Mr Rigby, the Upside chief executive, said the idea that an agent's commission had a direct correlation with getting the best sale price was "a myth".

"We are dramatically reducing the sales costs, while offering the same results," Mr Rigby said.