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John Reynolds, CEO of Castle Water asks what this tells you, and what to look at if you are thinking of switching
At the end of 2025, the operator of the business water market, MOSL, changed the way it reports on “Retailer Performance”. This is focused on meter readings, which is one of the most important components of customers receiving an accurate bill.
The latest official MOSL data shows that in total, Castle Water has 97 reads per 100 meters per month, compared with 49 for Everflow.
MOSL counts 7 retailers as large retailers, where performance should be broadly comparable. There are separate scores across technology (smart vs dumb meters), location (internal vs external) and frequency of read (monthly vs biannual). Meter reading of non-smart external meters is the most meaningful category for most customers: reading internal meters is very variable based on location within premises; smart meter reads are processed by water networks. Across this group of meters, there are significant variations in performance.
On the most recent data reported by MOSL, Castle is the third-placed retailer for six-monthly read meters with 90.47% success and the highest for monthly read meters with 89.45%. By comparison, Everflow has the lowest score for six-monthly read meters (mostly small customers – these are 99% of Everflow’s external meters) and Wave has the lowest score for monthly read meters.
Transfer Reads – Crucial for Billing Accuracy if you are switching
Transfer meter reads are crucially important for customers who switch supply – these make sure that the closing bill for your old retailer is correct, and that charges are correct for the new retailer. Where you use a retailer who bills entirely on estimates, such as Everflow, an incorrect or estimated Transfer read can make future billing inaccurate and volatile. According to official MOSL data, Everflow has taken 3,866 Transfer reads YTD, of which 3,502 are estimated – a staggering 91%. By comparison, Castle Water has used 338 estimated reads for Transfers (33%).
Castle Water maintains its own directly employed meter readers, giving us a unique ability to dedicate the time to visit and read meters, rather than paying contractors per read. As far as I am aware, no other water retailers invest the resources to do this.
Working Capital – Is this helping you or costing you?
Customers should also look very carefully at one of the areas not reported by MOSL, and on which there is no official published data, but which is crucial for ensuring you have a fair deal when you enter a contract for water services: are you paying in advance or arrears? Castle Water bills around 90% of customers in arrears, based on actual meter reads. Some other retailers, including Everflow, bill 2 months in advance. This means that in cash terms, in the first year of an Everflow contract, you would be around 25% worse off than with Castle!
What to ask your retailer
If you are considering switching water supplier, you should be asking:
- Am I billed on actual meter readings, and what is the retailer’s Market Performance Score?
- Am I billed in arrears or in advance (and how can an advance-bill be accurate, as it can only be based on estimates)?
- Will the new retailer take an accurate start read for my account (the new retailer’s start read automatically becomes the end read for the old retailer)?
