"That is a very big difference," Mrs Thomson said.
"There are a lot of things we could do with an extra $25 - there's quite a bit you could get in the supermarket with that," Mr Thomson said.
The couple see the discrepancy between the two discount rates as "grossly unfair" and are concerned the new policy will disadvantage older people and those on low incomes who may not have access to computers and internet banking.
"I feel sorry for many older and low-income people who struggle to pay their power bills anyway," Mr Thomson said.
"This move just disadvantages them further."
Contact Energy retail general manager Ruth Bound said there had been "a phenomenally positive response" from customers to the offer and the number of people now using the service was "increasing every day".
"Contact does not accept that the discount is discriminatory to either the elderly or those on low incomes as internet use and access in New Zealand households is extremely high," Ms Bound said.
The Statistics New Zealand 2009 Household use of Information and Communication Technology Survey showed that 75 per cent of New Zealand households had access to the internet at home and it was reasonable to assume that the percentage was even higher now, she said.
"People wishing to take up Contact's offer who do not have a home computer can easily access the internet at community facilities such as libraries and community centres or by using a relative's, family member's or neighbour's internet connection," Ms Bound said.
Meridian Energy retail general manager Bill Highet said, when contacted, that the company "would love to be dealing with all of our customers online" and did offer some incentives.
"However, we realise that not everyone has computer access and feel that it is a bit unfair to offer a discount that is so much higher to online customers," Mr Highet said.
While it was more expensive to post bills to people and deal with over-the-counter payments, Meridian handled this by charging a modest $1.50 fee.
Attempts by The Star to contact representatives of other power companies for comment yesterday were unsuccessful.
Contacted by The Star, a Commerce Commission spokeswoman said the issue of the Contact Energy online discount had been raised with the commission by other complainants. However, under the Fair Trading Act, it was permissible for a business to make such an offer as it was not misleading to customers.
"In this instance, there is choice for consumers," the spokeswoman said.
Grey Power national president agreed with the Thomsons the online discount was unfair and said the organisation had heard about it from "quite a few" members.
"It is unfair - there are a lot of elderly people who will never touch a computer," Mr Reid said.
