Power won't be restored until at least the early evening after a massive outage in the Taupo area.
Unison spokesman Danny Gough said around 16,000 customers had been affected and it would be several more hours until power was restored.
"It will be at least early evening until we havefull restoration. There has been a fault with a Transpower transformer at the Wairakei grid exit point."
Gough said Unison was doing all it could and there was 'great urgency'.
According to the Unison website thousands of customers have potentially been affected.
Gough said there was nothing Unison could do because it was the national grid that was affected but it was working with Transpower to get power restored as soon as possible.