Transpower says upgrading the Cook Strait electricity cable would come at a very small cost to consumers. 

It's consulting on a $1.4 billion proposal - to upgrade existing cables and allow for building a fourth.

CEO James Kilty says the plan is to get another 40 years of stable electricity. 

He says because costs will be paid for over that 40 years, prices won't surge. 

"It'll be a few dollars a year - but by the time it's spread across every connection in the country, it's spread over 40 years. It'll be a reasonably small amount."

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