The Electra website and app crashed unexpectedly during the outage due to high demand. Mr Simmonds said they will investigate the issue next week.
Meanwhile, Powerco has been working to restore power to about 2000 homes in the central North Island, mostly in Rangitikei and Manawatu.
Operations manager Phil Marsh said crews are working late into the night and will be back at work first thing in the morning.
"With the use of helicopters we have found major damage in the Central Plateau area and around Taihape and Mangaweka. The extent of the damage to rural and remote areas indicates that it might be several days before power can be fully restored.
"We hope to reduce those numbers again tonight and we will be back out there at first light tomorrow morning. We appreciate our crews for their efforts and we thank those that are still without power for their understanding in this difficult time."
Hundreds of homes on the Eastland Network were without power at 6pm, but the lines company said most people had their power back on by 8.30pm.
"We're pleased to say the power is now back ON for most people in the region. There are just a few areas that will be without power again tonight, with around 30 customers still affected in parts of Mohaka, Kakariki, Rangiahua and Hereheretau.
"We're sorry we couldn't get everyone's power on, but the weather has caused some significant damage. Our thanks to the crews, who will be back out again early Sunday morning to continue repairs, and to all the local residents who've been so patient for the last couple of days."
Hurunui Road and Herrick Road in central Hawke's Bay and Route 52 in Tararua District are closed due to flooding.
Slips, drop-outs and fallen trees are also affecting several other central North Island roads.
NZTA spokeswoman Karen Boyt said people should still continue to drive to winter conditions, and have a fully charged mobile phone in the car.
"If you are travelling over the weekend you should drive to the conditions and expect to see crews working on the roads.
"Now that there is a way through the central North Island a lot of people will be trying to use the roads so everybody should also be patient."
NZTA's rules for winter driving
• Allow extra time
• Ensure your vehicle is safe for winter driving
• Drive to the road and weather conditions
• Slow down and be prepared for unexpected hazards
• Allow greater following distance between you and the vehicle ahead
• Make sure your cell phone is well charged, check car charger also
• Have blankets, snacks, bottles of water ready in case of emergency or a breakdown.