The average price for a home this year in Mountain Ash was £137,220, compared to £104,431 a year ago.
Porth, in Rhondda Cynon Taf was second on the list, where asking prices rose by 26%, while Kirkby in Liverpool was third at 21%.
In Wales, average asking prices were up 10.5% compared with last year, followed by the South West (9.6%) and the South East (9.1%) of England.
Only St. Ives was in the top 20 for asking price hotspots from the South of England, with average asking prices having risen 15% this year, from £411,484 to £473,161.
Dalgety Bay, in Fife, Scotland was found to be this year’s quickest market, with homes finding a buyer in an average of two weeks.
A combination of sustained high demand and a shortage of properties means that competition between buyers has risen by more than a third during 2021 (36%).
Tim Bannister, director of property data at Rightmove, said: “This year has seen significant growth in average asking prices across so many areas of Great Britain.
“Strong competition for available properties, driven by low stock and high demand, has propped up asking prices throughout the year, and agents report that having multiple bidders for available properties will continue to be a theme into at least the first half of next year, although we do expect a better balance of supply and demand during the course of 2022, and some fresh property choice for buyers.
“With so many areas reaching asking price records, homeowners might be thinking that the new year is the time to take action and move, and maximise the return for their property.
“We’re expecting a wave of new buyers early in the new year, so we’d recommend this group who might be considering coming to market speak to their local agent for advice on making a new year move.”
