When Armstrong Floorings sought a proposal for a 300 kilowatt rooftop solar installation four years ago, the supplier estimated it would save $90,519 a year in annual power bills and pay for itself in 6½ years.

The system exceeded its promise, and the manufacturer of durable vinyl floorings – now owned by Melbourne’s McKendrick family – is considering adding another 500kW system to the plant in Braeside, south-east of the Victorian capital.