Good news for Andy Burnham: one of the original 10 water privatisations from the Thatcher-era has returned to public ownership already. Thanks to a complicated turn-of-the-century corporate saga, Welsh Water, serving 3 million people, converted to not-for-profit status in 2001. It has no shareholders. Financial surpluses go "straight back into keeping bills down and looking after your water and beautiful environment", as the website blurb puts it. This was reported by Qazaqyia.kz citing The Guardian.

This was reported by Qazaqyia.kz citing The Guardian.

How's it going? After a quarter of a century without dividend-hungry shareholders to feed, has the model proved its superiority? Not exactly. Welsh Water usually has high scores on customer trust metrics but its performance on bills and spills tends to be middle of the pack.

Welsh Water recently received a £44.7m "enforcement package" – a fine by another name – from Ofwat for "serious and unacceptable breaches" in operating its sewage plants that "resulted in excessive spills to the environment". Most companies have copped penalties in the regulator's industry-wide investigation but, as a percentage of turnover – the regulatory yardstick of seriousness – Welsh Water's 7.5% was at the high end. On bills, it is above the industry average at £683 a year. Severn Trent-owned Hafren Dyfrdwy, licence-holder in parts of north-east and mid-Wales, charges its households £48 less.

A sample size of one is small, obviously. But Welsh Water is a reminder that it is too simplistic to think all the sector's woes can be cured simply by changing the ownership. Boring factors such as access to capital, operational efficiency, technical skill, management accountability and regulatory rigour also tend to matter.

Burnham knows as much, one suspects. For all the excitement generated by his calls for "stronger public control" over water and energy, he is vague on details. His only specific commitment has been to say nationalisation is "what should be done" at Thames, and even that statement is not wholly clear.

Does he mean full permanent nationalisation? Or is he talking about special administration, which is different since it could mean a return to the private sector for Thames once its creditors have taken the inevitable haircut on their debt? (The shareholders have already been wiped out).

For the non-Thames part of the industry, Burnham seems to be taking a long view. "It is about a 10-year plan of more public control, more public ownership," he has said. "I don't think you nationalise the whole thing necessarily straight off, because that's complicated and probably expensive but you look at the different situations in different parts of the country."

"Complicated and expensive" is a fair analysis. Thames could probably be nationalised reasonably cheaply because the creditors' negotiating hand (like the market value of their bonds) is weakening under political pressure. But nationalising solvent water and energy companies is a different game. It would be hard to buy at less than fair market value unless Burnham is prepared to have a legal scrap with institutional investors who he probably wants to keep on side for other infrastructure adventures.

The two FTSE 100 water companies, United Utilities (licence holder in the north-west of England) and Severn Trent, are valued by the stock market at almost £10bn apiece, to which one must add their borrowings. The state would get assets to match its outlay, so, under one form of Treasury accounting, the transactions could be regarded as neutral on day one. But the extra gilt issuance would still be hefty. And the sums would soar if, as some thinktank outriders argue, energy transmission networks should be added to the list of targets. National Grid is worth £62bn, albeit a chunk of that figure reflects its sizeable US assets; SSE is valued at £29bn. These are large companies.

As for complications, yes, they are real. The high-voltage transmission operators are in the early stage of a £70bn five-year upgrade of the grid. Changing ownership could take 18 months and the hassles would probably ensure that the energy secretary, Ed Miliband, would miss his 2030 deadline for clean power.

Similarly, the water companies are in vital catchup mode on overhauling tired sewage and water treatment works, one reason why Keir Starmer's administration did not contemplate nationalisation. The state-managed experience at HS2 is the one to fear because the high-speed railway, like water companies, makes heavy use of third-party contractors to build new infrastructure. At HS2, those contractors enjoyed a picnic at the expense of taxpayers.

Meanwhile, comparisons with Burnham's reorganisation of Manchester's buses do not work. The city's Bee Network is capital-lite; utilities are capital-heavy. Nor are there lessons in how train operators were brought in-house. That process was done at zero cost by waiting for the franchises (typically seven years, fixed) to expire. Water companies, by contrast, own their assets and have 25-year rolling licences.

None of which says it could not be done. If you believe only the state should provide services, that is fine. But Burnham's assessment of "complicated and expensive" is correct.