UPDATE 1-Small business owners count cost of South Africa's power cuts

* Small businesses forced to use costly generators

* S.Africa suffered unprecedented power losses this week

* Problems at power utility Eskom threaten economy (Recasts with business in Alexandra township)

By Kara van der Berg and Onke Ngcuka

JOHANNESBURG, Dec 11 (Reuters) - When South Africa suffered unprecedented power cuts this week as flooding slashed thousands of megawatts off an overstretched grid, dry cleaner and shoe repairer Eva Ntleve had to stop work.

"It's affecting us very badly," she said at her store in the township of Alexandra, one of Johanneburg's poorest, where small shops selling second clothes and phone credit line the streets.

"When the power goes off we can't work, him especially," Ntleve said, gesturing towards a man sitting next to an idle shoe repair machine. It, like the spin washers, were taken out by crippling power cuts across South Africa this week.

A week of floods has aggravated problems at state-owned utility Eskom, which has been struggling to keep the lights on since 2008, triggering unprecedented levels of planned power cuts known as "load shedding".

For bakery owner Maike Vandereydt-Speer it meant being unable to brew coffee, toast sandwiches or switch on the lights.

One of her two bakeries already has a generator -- which costs at least 3,000 rand ($200) a day to run -- but she had balked at the cost of installing one at her Black Forest bakery in the leafy Johannesburg suburb of Parkmore. Now she is considering it.

"If we do not have a generator we basically close down," she told Reuters. "We hope the business can survive," she said, noting that her business was losing 1,000 rand a day.

Economic fallout from the power blackouts is widespread with large-scale mining companies shutting down across South Africa on Monday, but they are better placed to weather the storm than more fragile smaller businesses.

"It's devastating, absolutely devastating," said the CEO of the Johannesburg Chamber of Commerce, Joan Warburton-McBride. "Especially at this time of the year when small traders were hoping for a turnaround to a very bleak year."

Magur Patel, manager of a green grocer in Alexandra, told Reuters he was losing 20 percent of his income on every day there was a power cut -- he had lost up to 20,000 rand this month, he said.

"The veggies I have are in the cold room, so when the electricity is not there ... I lose some of them," he said.

Back in Parkmore, locksmith Boris Milwidsky complained that he was running an expensive generator that didn't produce enough power to run all his machines.

He estimated his losses from the purchase of costly generator fuel and lost output at around 60,000-70,000 rand a day. He declined to say what his total revenue was.

"The generator can't fuel everything," he said. "Every single part of our business works on electricity."

($1 = 14.7075 rand)

(Writing by Tim Cocks; Editing by Kirsten Donovan and David Evans)