Housing market experts said growing uncertainty around the autumn Budget has had an impact on sellers' sentiment across the UK.
Figures from the Office for National Statistics show the average Powys house price in the year to August was £235,050 – a 3.9% increase on July.
It was higher the average across Wales, where prices increased by 1%.
The rise in Powys contributes to the longer-term trend in the area, which has seen property prices in the area grow by 1.3% over the last year.
It means the area ranked 14th among Wales’s 22 local authorities for annual growth, with the average price in Powys rising by £2,900 over the past year.
The highest annual growth in Wales was in Bridgend, where property prices increased on average by 6%.
At the other end of the scale, properties in Merthyr Tydfil lost 8.5% of their value.
Across the UK average house prices increased 3% in the year to August, reaching £273,000 typically.
The rate of annual growth slowed from 3.2% in the 12 months to July.
However this varied across nations.
Average house prices rose 2.9% to £296,000 in England for instance, and jumped 4% to £194,000 in Scotland.
The figures were released as the ONS said Consumer Prices Index inflation was 3.8% in September, remaining at the same level as both July and August.
James Evans, chief executive at estate agent Douglas & Gordon, said: "Many buyers who hit pause earlier in the year are now back in the market, encouraged by more stable rates and improving affordability.
"It’s a positive sign, but we’re not out of the woods yet. Policy uncertainty ahead of the autumn Budget is already making some buyers cautious, particularly at the higher end."
Colleen Babcock, a property expert at Rightmove, said: "A decade-high level of homes this year has limited the growth of house prices compared to last year.
"Buyers have more choice and more negotiating power, and we’re seeing more realism from sellers about the prices they can set to find a buyer amongst the competition.
"However, prices are holding up more strongly in the north of England, Wales and Scotland, where more affordable price points means that changes to stamp duty charges from April have had less of an impact."
Stamp duty applies in England and Northern Ireland.
Simon Gerrard, chairman of Martyn Gerrard Estate Agents, said: "These figures from August represent sales from earlier in the year and don’t show the slowdown that set in once Budget speculation started.
"People aren’t making property decisions until there’s clarity on what new measures are coming."