Supplies are gradually being restored after last week's severe winds but more than 4000 properties in the South remain without electricity.
Emergency Management Otago group controller Matt Alley said the damage was so widespread "power outages for remote areas could last weeks"
"With one instance of five kilometres of cable needing to be laid to restore power for just two houses, this is intense and intricate labour, an exhausting long haul for power crews."
PowerNet Chief Executive Paul Blue said at noon today, about 3400 customers in Southland and 1674 customers in Otago remained without power.
By the day's final update at 5pm that had fallen to 2900 in Southland and 1650 in Otago.
He said they appreciated that it had been a long time for those still without power.
"Our focus has been on ensuring critical services are powered, large urban areas and the region's dairy farms.
"Some of the areas still to be restored do have extensive damage, but we also know there are likely to be many individual properties who have suffered more localised damaged and are still without power. Until this stage, we have asked them to be patient and not report these individual issues."
Blue said while the restoration of power throughout Otago and Southland was tracking well, the response was likely to have a long tail.
"We've largely reconnected our biggest areas of customers, but we have some very complex and widespread issues affecting many of those remaining. We will have a much better understanding by Friday of exactly how long those people can expect to wait for their power to be restored."
Urgent conserve water notices had been issued this morning for Lawrence, Tapanui and Clinton.
The rest of the district remains on a precautionary boil water notice (except Balclutha, Milton, Waihola, Kaitangata and Wangaloa).
Lawrence reservoir was critically low at 18% while Tapanui reservoir was also low at 39% of capacity.
"The whole district should be conserving water where they can and avoiding any activities requiring a large amount of water."
Clutha District Council today announced a contribution of $100,000 to Clutha's Mayoral Relief fund for those affected by the devastating weather event.
The council's contribution would increase the total of the fund to $150,000 which included Central Government's $50,000 contribution announced on Monday.
Mayor-elect Jock Martin is asking councils from throughout New Zealand to contribute to the fund.
Emergency Management Southland said about 30 generators were being circulated in the community to support critical infrastructure, dairy sheds and community hubs.
Invercargill's Mitre 10 manager Tracy Key said the store had stocked up on more than 200 generators over the weekend knowing the demand would be huge, and they had been flying off the shelves.
"It was nice to put some smiles on faces for sure. There are some people who were a wee bit teary when you said how's it been for you, and you can certainly see the emotional drain that it has taken," she said.
A state of emergency remains in place in Southland and Clutha, and a boil water notice is in place for most of the Clutha district.