The Employers & Manufacturers Association says it is not enough for retail power companies to freeze the price of electricity; they should be dropping it because supply is now outweighing demand.
Mighty River Power last week announced it was freezing its prices for residential customers until at least April 2015.
But EMA says the futures price of wholesale energy - that is, the price from next April - is set to decrease by 0.17 cents per kilowatt hour.
Chief executive Kim Campbell says lack of competition in the market may mean the decrease is not passed on to customers.
The Electricity Authority says there has been competitive discounting in the past year, but official statistics do not reflect that.
