Monmouthshire was among the local authorities to see the largest gains with 77.5 per cent gaining £65,000 or more. The median gain over 20 years was £129,600 and the average house price in the county was £330,500.
The research also found that homeowners from across the UK who sold their home in the last 12 months, made on average £65,000.
In Wales 58 per cent of homeowners were sitting on up to £75,000 in unreleased gains with the average price of a house being £205,800.
However, homeowners do not necessarily need to reside in their home for decades at a time in order to benefit from substantial gains.
Nearly half (48 per cent) of homes purchased in the last ten years have increased in value by over £65,000, increasing to 55 per cent in Southern England.
In the South West, 58 per cent of homes experienced gains of over £65,000, the highest proportion in the UK, followed by the South East (57 per cent) and the East of England (53 per cent).
Izabella Lubowiecka, senior property researcher at Zoopla, said: “Millions of UK homeowners are sitting on tens of thousands of pounds in property value gains since they moved into their current home, despite recent falls in house prices.
“For many, meaningful capital gains can provide important financial support for their next home move. Those thinking of selling should get their property valued sooner rather than later, they never know, they could be sitting on a small fortune.”
