Each day that bushfire smoke descends on Sydney and workers down tools while shoppers stay at home, estimates by SGS Economics and Planning show the city's economy bleeds up to $50 million.

As firefighters battle to contain blazes, economists are beginning to tally the cost of lost worker output, transport interruptions and reduced spending.

Smoke blankets Sydney on November 19. Credit:Neil Bennett

Sydney is Australia's most concentrated area of economic activity and shutdowns and disruptions caused by smoke are having "a real impact", said Terry Rawnsley, an expert in regional economics at the consultancy SGS Economics and Planning.

"Sydney generates around $1.2 billion dollars of income every day," Mr Rawnsley said. "Based on the nature of the these extraordinary events, Sydney's gross domestic product was probably reduced by around $12-$50 million each day."