Some Christchurch landlords are offering a week's free rent to attract tenants as rental prices in the city reach their lowest point in three years.

Tenants on average are paying nearly 10 per cent less rent than a year ago, with high levels of building and earthquake repairs boosting the city's housing supply and forcing owners to absorb extra costs.

According to government bond figures, the city's median weekly rent is now $383. This is 12 per cent lower than the high of $436 reached early last year and comparable to 2013 levels.

New laws required rental homes to have smoke alarms by July 1 this year and ceiling and floor insulation by 2019. There has been speculation that this, along with rising rates and insurance costs, could push up rents.

Tony Brazier, owner of property management company Braziers, said there were too many homes available to allow rents to rise and an over-supply could be looming.

"Just because landlords' costs go up, they can't just pass them on. They have to absorb the extra."

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In the past few months they had even started offering a week's free rent to attract tenants, he said.

"There are more than enough properties out there to rent, so there's no pressure building on rents. It's a much fairer market than it was three years ago.

"The market's getting softer and softer and it's teetering on being in the tenants' favour."

Brazier said that many landlords did not mind rents being flat as they were still getting increases in property values.

However, some were reluctant to lower rents when looking for new tenants, and as a result they could be left with empty premises, he said.

A search of To Let advertisements reveals there are now about 1750 homes for rent in Christchurch. This compares with a low of 540 in February 2013 and about 1300 before the earthquakes.

Patricia Bowden, co-owner of letting agency Harcourts Accommodation in Christchurch, agreed there was no upward pressure on rents in the city yet.

"A few months ago rents dropped well down and the market has evened up."

However, she thought that a "very slight" increase in rents could come next year when the combined effect of higher insurance premiums, increased rates, methamphetamine testing and insulating homes would start to be felt.

Both Brazier and Bowden said the exception to the easy availability of rental homes was the bottom of the market, especially with many old and cheaper homes lost in the earthquakes.

Head of Trade Me Property Nigel Jeffries said in his latest report that Christchurch was the only city to have "a significant downward trend in rents" in the past year. Other cities had recorded steady rises.

While some parts of the country had rental increases reaching double figures, Christchurch rents had fallen 9.1 per cent in the past year, according to TradeMe figures.

The government bond figures, collated by the Ministry of Business, Innovation and Employment (MBIE) show Christchurch's highest median rents are about $460 in and around the pricey suburbs of Cashmere and Fendalton.

Addington, where rental homes are mostly units and apartments, has the cheapest weekly rents with a median of $265.

New Zealand's highest rents are in the northern parts of Auckland city and in Queenstown, both with averages over $500. The lowest rents are in the Tararua district in the lower North Island and Buller district, both well under $200.

AVERAGE WEEKLY RENTS:

Addington $265

Aranui/Bromley/Bexley $375

Avon Loop/Central city east $330

Avonhead/Yaldhurst $450

Bishopdale/Papanui $417

Burnside/Harewood $437

Burwood/Dallington/Avondale $395

Central city/Hagley $380

Fendalton/Strowan/Bryndwr $460

Halswell/Wigram $450

Hillmorton/Hoon Hay $420

Hornby/Islington/Hei Hei $410

Ilam/Westburn $440

Linwood/Phillipstown $320

Marshland/Redwood $430

Merivale/St Albans west $380

North Beach/New Brighton/Southshore $379

Redcliffs/Sumner $450

Riccarton $380

Richmond/Avonside $350

Richmond/Shirley $400

Sawyers Arms/Northcote/Belfast $420

Sockburn/Upper Riccarton $410

Spreydon/Somerfield $400

St Albans east/Edgeware $350

St Albans North/ Mairehau $420

St Martins/Beckenham/Huntsbury $440

Styx/Parklands $450

Sydenham/Waltham $360

Westmorland/Cashmere/Barrington $460

Woolston/Opawa $375

(source: MBIE)