Brenda Kelly’s home is in a slightly shaded spot, and she doesn’t have solar panels – yet she can’t remember ever having an electricity bill over $60 a month.

The secret? She lives in a 43.2 square metre house.

The average size of a newly built home is 156sqm, down from a 2010 average of 200sqm and not yet back at the 1974 level of 109sqm (although this did not usually include an attached garage).

But with the cost of living rising, there are undeniable savings to buying – or building – smaller.

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Kelly has been living in her two-bedroom place in Taupō, built from three 20-foot containers, since 2019.

Her power bill doesn’t include her hot water – that’s on gas, and she says she gets through a 9kg bottle every 6 to 8 weeks, which she estimates adds up to approximately $23 per month.

But she says her electricity bills for heating her two-bedroom place could be even lower, except she runs the heat pump to keep her 20-year-old cat, Sparky, warm.

Hutt City Council eco design advisor Gregory Street​ says energy costs are the main saving from living smaller.

“How much energy used is per square metre and will inevitably increase as size increases,” he says.

But as well as lower energy costs, smaller homes have fewer ongoing maintenance costs – such as painting, she says. Another saving? Not buying as many possessions.

“You don’t accumulate as much. You have a few sentimental items that mean a lot without hoarding.”

Having built two of her own homes from 20-foot containers, Kelly runs IQ Container Homes, designing and facilitating builds for others.

She says clients can struggle with the fact the small homes cost more per square metre upfront – due to having expensive areas (bathroom and kitchen) included, as well as the fact they are insulated to a high specification (walls with a minimum R-value of 3).

But she says it’s well worth it for ongoing savings over the long life of the building.

Architectural designer Edd Coomber had finances front of mind when he bought an 80sqm 1970s Christchurch townhouse in 2019.

“Budget at the time of purchase was definitely a big factor,” Coomber says, “but absolutely I was thinking that a smaller house is easier to heat.

“Mainly, it’s about only taking my fair share of the pie: I don’t need a massive house I’ll never use.”

Ongoing loan repayments are another obvious lower cost for a smaller, cheaper home.

At the time he bought, Coomber’s repayments for the two-bedroom home were less than it had cost him to live in a shared flat in Auckland – $465 fortnightly home loan repayment compared to $600 in rent (for a room in a place shared with two others).

His summer power bills are about $70 a month, a figure that doubles in winter, including for his last bill.

“I did have my mum staying, and she’s from Melbourne so she cranked the heat up.”

When looking at new builds, Street says house shape is also important.

“Form factor” – or the complexity of the shape of a house – determines external surface area and so heat lost to the outside, he says. Smaller houses are typically less geometrically complex.

“A small house would lend itself to a more simple shape and have fewer external surfaces to lose heat,” he says.

Street says large houses are generally built large “for the benefit of the developer”, or simply on the assumption that more is better.

“It is not necessarily done to match design and spaces to the needs of the purchaser.”

He gives the example of 250sqm houses in new developments in Paraparaumu that have been built for only one or two occupants.

“The old state houses were generally 85 to 95sqm for three bedrooms, but did tend to have poky small rooms - and the small rooms made it hard to get the heat around. They weren't centrally heated.”

Street says our obsession with windows is another factor in energy efficiency.

He says people are being encouraged in our desire for “unlimited glazing”, quoting building scientist Jason Quinn, from Sustainable Engineering, who says floor-to-ceiling windows are only for dogs with short legs.

Julie Villard, an eco design adviser with Christchurch City Council, lives in an ultra-energy efficient two-storey home in Lyttelton.

While the upfront cost of building with high standards for insulation, performance glazing and ventilation is higher, the 120sqm home is cheap to run.

Villard and her husband are never cold, have a house that is heated in every room, and still have winter power bills (August and September) of about $160. In summer, that drops to $67. Their average monthly bill is $125.

“And I have a wine fridge,” Villard points out: “Just to say, it is doable.”

Villard’s calculations show energy use varies hugely depending on the size and how well insulated a house is.

Estimated costs to heat a home per year (using 30c/kWh as price of power, not including connection charges)

Well-insulated home – to Homestar 6 standard

House built to Passive House standard

This story has been amended to clarify that Kelly’s monthly power bill does not include her gas hot water.