Thames Water insane price hiking

Sptz

Hi everyone,

I’m seeking advice on a frustrating Thames Water bill issue. I’m a single occupier (alone since early 2024) in a smallish 2-bedroom flat in their area, no water meter. My annual bills have spiked sharply:

•  2026 (for 01/04/2026-31/03/2027): £990.24

•  2025: £923.61

•  2024: £682.54

•  2023: £609.28

•  2022: £551.22

•  2021: £530.98

•  2020: £474.97

That’s a 35% jump from 2024 to 2025, and another 7% to 2026… far above typical increases. No changes in my setup or usage.

In chat support, they said it’s “Notional Value” (NV) based on location and bedrooms (not occupants), with a breakdown assuming 230m³ volume (way high for one person).

Their website shows assessed charges by bedrooms (lower than mine):

•  Zero/One: £626.34

•  Two: £660.41

•  Three: £724.36

•  Four: £775.26

•  Five+: £842.99

They suggested a meter for actual usage but didn’t explain the hikes or mismatch. Just completely avoided answering my questions.

Asked AI about NV which stated NV is a 1990s proxy rateable value; assessed charges (post-meter request if unfit) use bedroom-based volumes, with a single occupier option (~£552 for 2026/27) if proven (e.g., council tax discount).

Questions:

1.  Is my NV bill correct? Why much higher than assessed 2-bed (£660.41). Can I challenge the NV?

2.  How to switch to single occupier? Request meter first; if impossible (common in flats), get assessed then single rate? Proof needed?

3.  Can switches/refunds be backdated? Overpaid since 2024 relative to single rates.

4.  Anyone challenged similar NV spikes, switched, or got refunds with Thames Water? Escalation tips (CCW/Ofwat)?

This feels unfair for a solo occupier paying essentially a 5 bedroom family… add to that they’re unwillingness to provide any clarification on why the price hikes etc…

Any insights would be greatly appreciated!

Many thanks

MattMattMattUK

https://forums.moneysavingexpert.com/discussion/6656573/thames-water-insane-price-hiking

1 The NV is almost certainly correct, no you cannot challenge it.

2 Yes you can be asked to be put on the single occupancy rate, you just need to ask, but far better to get a meter installed as it will be considerably cheaper. The proof would be your council tax bill showing only you as the occupant. It is fairly uncommon now for it not to be possible to fit a meter, if that does end up being the case you would be moved to a assessed charge, which is slightly over what they estimate metered usage to be for a similar property (it will related to the number of people living there, garden etc.).

3 No.

4 The NV does not change, the billing rate for those properties does. No refunds. No grounds for escalation. Nothing to challenge.

Essentially NV/rateable is based on a worse case high usage scenario, if people want to save then they should have a meter fitted.

Sptz

https://forums.moneysavingexpert.com/discussion/comment/81896221#Comment_81896221

Thanks for the prompt reply!

Regarding 3. So they can just hike 35% out of the blue and get away with overcharging massively? Zero recourse?

James_Londoner

There has been a lot of news coverage over the past few years about Thames Water's dire financial situation and it seeking (and being given) permission to put up bills more sharply than would generally be the case.

MyRealNameToo

https://forums.moneysavingexpert.com/discussion/comment/81896233#Comment_81896233

No, but it's not out of the blue. Ofwat reviews pricing every 5 years, occasionally there are exceptional processes hence there was the release over a year ago saying that bills will be going up an average of 26% https://www.ofwat.gov.uk/average-bills-2025-26-press-statement/

Thames are in a problem on a number of levels, their increases were always anticipated to be some of the highest as a consequence.

mark_cycling00

There is no recourse for an individual.

Ofwat can step in if they think price increases for non-metered customers are too high but they have not done this to my knowledge.

30%+ annual increases are commonplace.

I used to pay £25 a month a few years ago and now it's £60. I don't pay for waste water or rain water.

MattMattMattUK

https://forums.moneysavingexpert.com/discussion/comment/81896233#Comment_81896233

Your issue is that they have not been overcharging. Single occupancy is something the bill payer is required to request, it is not a default. Whilst water suppliers are not forcing meters to be fitted and they have been in all new builds for some time if someone is on rateable then it is largely down to them to request a meter is installed.

With regard to the percentage increase these were approved by Ofwat when accounting for the need to invest in the infrastructure, following direction from government. Essentially water bills have been held artificially low for decades, that has meant underinvestment, which now means we need accelerated investment to catch up and fix things.