Both Hyundai and its Kia affiliate reported rapid growth in sales of hybrids in its domestic market with almost one in five Hyundai Sonata and one in 10 Kia K5 buyers opting for the hybrid versions in July.

Sales of the Sonata and K5 came to 7,772 and 7,051 units respectively last month. The company has set a target of selling 11,000 Sonata hybrids and 6,000 K5 hybrids this year and is now confident that it will reach that goal, according to a company spokesman.

This is despite the KRW3m (US$2,850) premium for the hybrids over the regular petrol models which the company estimates customers will get back if they drive 20,000km (12,000 miles) in the first five years thanks to the 21km/litre (about 60mpg) fuel consumption of the hybrids.

The Sonata and K5 hybrids use a lithium ion polymer battery pack which the company says has 63% higher power density and 13% higher energy density than nickel-hydrogen batteries used in other hybrid cars available on the market. The pack is also 25% lighter.

The sales success in South Korea follows encouraging results in the US for Hyundai where the Sonata hybrid is gaining ground on the market leading Toyota Prius. In June, Sonata sales were 1,422 against 4,340 for the Prius – and while that gap appears large, the Sonata outsold other hybrids including the Toyota Camry, Honda Insight and Ford Fusion.