State housing tenants are resorting to bubble-wrapping windows, using ovens as heaters and sleeping in one room to stay warm - because they say the heaters provided are simply not suitable.
Social housing providers have installed tens of thousands of 2000 watt electric convection panel heaters in state houses, but tenants complain they are not fit for purpose.
Even when curtains and windows were closed and the houses were insulated, they could not get their houses warm, tenants have told RNZ.
The manufacturer, which RNZ has chosen not to name, said there was nothing wrong with its heaters and there was more likely to be issues with insulation or the way tenants were using the heaters.
It said all electric heaters of the same wattage in a similar sized space would heat the room in the same way.
In a statement, the manufacturer said it supplied about 15,000 units to Housing New Zealand (HNZ) each year and "can count on one hand" how many complaints it had received.
The heaters, which have an inbuilt thermostat, were designed to slowly heat a room over time and maintain the temperature, it said.
But some tenants had taken to social media to voice their frustrations and some told RNZ they stopped using the heaters altogether.
One woman, who RNZ will call Mary, lives with her grandchild in a Housing New Zealand house in West Auckland.
Despite it being a sunny and warm day outside, inside the house is cold and damp. Mary is wrapped up in a heavy wool coat and warm socks.
On the living room wall is an electric convection panel heater.
Mary said she tried using it to heat the living room but it had taken too long.
"It took about three days to even get warm slightly and it certainly doesn't warm the room it's in."
She has started using an oil-heater and two-bar electric heater alongside the on provided, before deciding to turn off the electric heater all together.
Mary said she told her HNZ tenancy manager that the provided heater was ineffective in the space.
"I think HNZ should set the example of doing thing right by their tenants.
"Without adequate heating, people are getting sick."
Mary was not alone.
Karina Tipene, another HNZ tenant, has lived with her extended family in a 5 bedroom house in Pakuranga for 3 years.
When she moved in, the house had both a fire-place and the same type of electric heater, but the fire-place was removed soon after.
"The heater installed here is not effective.
"Even if we were to close all the doors and block everything off, there's no heat there. You literally have to stand in front of it before you can feel something."
Ms Tipene asked for a heat pump but was denied.
"If you could have one central heat pump to warm up the house, children would be comfortable to sleep, you'd be comfortable sleep - it would be just perfect.
"But in some places, there's not always perfection."
The family has stopped using the heater and instead are layering up on clothing and turning on the oven.
The cost of heating was not worth the heat output, she said.
Instead, children all slept in the lounge together to stay warm.
"They're asthmatics, I have heart failure and asthma, but there's not much we can do in terms of staying warm," Ms Tipene said.
Ms Tipene said the house was damp.
Another tenant, who RNZ will call Gina, lives in Glen Innes with her intellectually disabled family member in a home run by Tamaki Regeneration.
She said the provider finally installed a fan heater after she kicked up enough of a fuss.
Until then, there was just the electric convection panel heater.
"We have quite a large lounge and dining area and it just absolutely gives no heat whatsoever.
"There's no point in putting it on because it doesn't heat the room it's supposed to heat."
Tamaki Regeneration Company (TRC) provided the added heater after Gina complained that her asthmatic, intellectually disabled family member was living in a mouldy, cold room.
"I pulled her out of that bedroom and put her in with me."
The new fan heater in the hallway was "brilliant", she said.
"It think they need to address the heaters they are currently buying - that wall heater does not service the room that it's in."
Gina said TRC was trying its best to address concerns.
"They have listened to what I've said and there is a difference in the house."
The crown entity, Energywise, breaks down the most efficient and cost effective way to heat a home on its website.
According to Energywise, electric panel heaters were only considered suitable for a small space, but were more expensive to run and their heat output low compared to most other options.
Electric convection panels were better at circling heat through a room but struggled to heat rooms with high ceilings, the website said.
So why are people going cold?
The manufacturer of the heaters installed in HNZ properties said heaters of this wattage should heat a room well and there must be issues with insulation or with the way the heaters were being used.
TRC chief executive John Holyoake said its tenants were taught how to use the simple two dial heater.
The electric convection panel heaters were used as a standard across their 3000 properties but some houses had more heaters than others, he said.
The company looked at a room's size and heating requirements when settling on a type of heating device.
Mr Holyoake said he was not aware of complaints and said there could be other issues at play.
"We definitely have issues with older properties. They aren't airtight and they are cold and damp.
"We are replacing all of the old houses, but that's going to take time though."
Mr Holyoake said he would investigate the heaters and change them, if necessary.
"It should be cost efficient for the tenant and keep them warm and healthy," he said.
In a statement, HNZ said some houses were old and not built to fit the New Zealand climate.
It said it used both the panel heaters and fan heaters but that "neither type of heater will warm a whole house without all the other factors such as air-tightness, insulation and other thermal improvements".
Work in this area was ongoing but it already provides extra heating for its most vulnerable tenants.
HNZ declined to comment on whether it received complaints about the heaters, or how it chooses its heaters. It also declined to reveal how much the heaters cost.
The manufacturer said fan heaters were better at providing instant warmth to a cold room.