Britain’s homes could be worth as much as £9.2tn on the open market – four times the value of the UK economy, and £550bn more than this time last year, it has been claimed.

House prices have soared since the restrictions on homebuying started to be eased in the spring of 2020, fuelled by stamp duty breaks and a rush for larger homes. The lowest mortgage rates on record have also passed through to higher prices.

The property website Zoopla said the recent boom meant that Britain’s housing stock had risen in value by 20%, or £1.6tn, since 2016, and that the average home was now worth almost £50,000 more than five years ago.

The estimate is based on the website’s “automated valuation model”, which takes into account sales recorded with the Land Registry each month and combines these prices with other factors including details given by owners and information about schools and crime rates. It includes all 28.6m homes in Britain, not just those that have recently sold.

The figures underline the gulf in prices in different parts of Britain. Zoopla estimates that in Westminster and Kensington and Chelsea, two London boroughs spanning 13 sq miles, the combined value of homes is roughly the same as for the whole of Wales.

Homes in Westminster were estimated to be worth a total of £165bn, making it the priciest borough in Britain, while those in Kensington and Chelsea were put at £141bn.

Official figures from the Land Registry show that in Westminster the average price of a property was £898,000 in July, 3.1% down on the previous year.

However, the borough still lays claim to some of the most eye-watering prices in London – current listings include a 12-bedroom Mayfair townhouse on the market for £54.5m and a six-bedroom mansion with an asking price of £40m.

The report also breaks down the value of housing stock in each region and compares it with the volume. This shows that while 12.7% of homes are in London, they account for 25.3% of Britain’s housing value. For the north-east it is 4.4% of homes and 2.1% of the total value.

The report’s authors, Gráinne Gilmore and Izabella Lubowiecka, wrote: “Over the last five years, the total value of homes has risen by £1.66tn, more than five times the total value of all GB housing transactions in 2020. It is also around the same value as the market cap of Apple, which is the world’s largest company by value.

“The rise in values since 2016 signals modest but sustained annual house price growth across the UK since then, underpinned by low mortgage rates, which has resulted in a cumulative 20% uplift in the value of housing.”

Neal Hudson, housing market analyst at BuiltPlace, said the figures showed the disparity in housing wealth and how it was concentrated in London, and underlined the “massive amount of money” in housing.

However, he added: “The value of a home is what a buyer is willing to pay for it … If everyone decided to move out of their homes and they all tried to sell at once then it’s highly unlikely that they would be worth £9.2tn.”

Although prices dipped since the big stamp duty breaks came to an end in June, there have been signs that a mismatch in demand for homes and supply of properties for sale could push them up again.

The latest report from the Royal Institution of Chartered Surveyors (Rics) showed that, after a “brief pull-back” as the stamp duty deadline neared, buyers returned to the market in September.

The lack of available stock was creating competition among buyers, it said, and as a result 68% more of its members reported price rises than reported falls.

Simon Rubinsohn, Rics’ chief economist, said: “The imbalance between demand and supply remains the most striking theme in the latest Rics residential market survey. And feedback from members provides little reason to believe this issue will be resolved anytime soon.”

He added: “Delivering higher numbers of new homes is part of the answer but it is critical they are built in the areas where the shortfall is most visible. It is also vital that the tenure mix of the supply pipeline is broadly based helping to address the challenges both in the private rental market and in social housing.”