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The electricity market is maximising profit at the cost of people's health, even while demand is declining, energy analyst Molly Melhuish says.
Meridian Energy has reported a 3% drop in energy usage in June compared with the same time last year, but says this does not mean power prices go down.
Lake levels were high in the North and South islands, following the highest June monthly inflows into Meridian's catchments in the past 10 years, Meridian said in its latest monthly operating report.
A warmer-than-usual winter, home insulation, and people cutting power use to save money were all factors in the decline, Mrs Melhuish said.
Figures out this week show electricity prices across the board rose 2.3% in the year ending March.
The lowest annual rise since 2001, it was evidence National's electricity market reforms had worked, Energy and Resources Minister Simon Bridges said.
People were using less electricity because they could not afford it, while the push for more home insulation was having an impact, Mrs Melhuish said.
She urged people to keep warm, because it was vital for health.
''Put keeping warm at the top of your list.
''If you have to use more power to keep warm enough so that you stay healthy and active, then just pay the difference and complain like mad.''
The impact on older people of high prices amounted to ''elder abuse''.
Other countries, with some exceptions, had seen the end of power price rises because of flat demand.
In New Zealand, the system was set up to extract as much from possible from customers.
Power companies were charging more than the market could bear, borne out by people reducing their usage.
It meant more people would get sick, while those who could afford it would improve insulation in their homes.
Mrs Melhuish warned Labour's policy to push higher-spec smart meters, in a bid to lower prices by encouraging appliances to run during the night, might not lead to lower prices.
''Until you change the objective of electricity pricing, which is now to allow profits to maximise, no technology will get around the fact that they will go on profiteering until they are told they can't.''
The value of dehumidifiers should be emphasised more, she believed.
They were relatively energy efficient, and made rooms more comfortable by reducing moisture.
''A dehumidifier will turn nasty moisture into nice heat.''
She suggested poverty action groups dehumidify people's homes with a high-capacity machine for a couple of weeks, after which a standard store-bought machine could be used.
Energy Efficiency and Conservation Authority senior technical adviser Christian Hoerning said dehumidifiers worked best in warm rooms.
The authority preferred people fixed the source of dampness, rather than running a dehumidifier, although they did have a place.
Green Party energy spokesman Gareth Hughes said power prices had risen above inflation.
''This is even less acceptable, given demand has been slack in the electricity market. It shows the market in its current form is not working.
''While the big power companies profit, families and businesses are hurting. Something has to change.
''Excessive electricity prices are a deadweight on our economy and a drain on strained family budgets.''
Meridian media manager Michelle Brooker said the South Island hydro storage lakes were 75% full. That compared with 73% the corresponding time last year.
Higher hydro flows did not translate to lower prices, although Meridian did not expect to increase electricity prices until at least June next year.
- Additional reporting: Rebecca Fox.