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London has roughly 600,000 businesses and around 150,000 of them are non-household water customers. Wholesale supply is mostly Thames Water with parts of north-west London on Affinity Water. Despite the open market since 2017, the majority of London commercial water customers are still on whichever retailer they were assigned by default.
You can switch retailer. London businesses have had that right since the market opened in April 2017. Most never have.
This page covers where London business water costs come from, how the wholesaler/retailer split actually works in the capital, and where overpayment usually hides on a London bill.
- England’s non-household water market opened to competition on 1 April 2017, giving every London business the right to choose its water retailer.
- Wholesale supply for London is mostly Thames Water; parts of north-west London (Hertfordshire/Essex side) are supplied by Affinity Water. Wholesale doesn’t change when you switch retailer.
- A typical London business contracts directly with one retailer; multi-site operators can contract centrally across the entire London estate for portfolio pricing.
- A typical London independent business spends £600–£2,400 a year on water; busier hospitality and multi-site operators run higher.
- The three biggest London-specific savings levers: surface water drainage on dense urban sites, Thames Tideway pass-through review, and tariff renegotiation.
Why London businesses overpay on water
London is unusual. Around 95% of central and Greater London is supplied wholesale by Thames Water; the remaining western and northern suburbs (parts of Hertfordshire, Essex and Surrey-side LBs) are supplied by Affinity Water. Both wholesalers set different supply rates, and the open-market retailer you choose can only offer pricing within the wholesaler’s standard tariff — what they compete on is retailer margin, billing accuracy, account-management quality, and the audit work behind your invoices.
On top of that, every London business water bill now carries a Thames Tideway tunnel charge, the long-standing surface water drainage charge that’s often miscalculated on dense urban buildings, and a Greater London Authority business-rate-linked levy on some larger sites. None of these are obvious from a glance at the invoice, and most have refunds available going back six years.
The five places London businesses overpay
| Where London businesses overpay | Why it matters in the capital |
|---|---|
| Surface water drainage on dense central buildings | Charged on building footprint regardless of where rainwater actually goes. Many central-London buildings drain to private soakaways, internal drainage to combined sewers, or attenuation systems. Rebate-able with a drainage survey. |
| Thames Tideway tunnel charge applied flat-rate | Every Thames Water customer pays this; some retailers absorb part of it, others bill it as a clear pass-through. Worth comparing. |
| Default Thames Water tariff that nobody renegotiated | When the market opened in 2017, most London businesses stayed on Thames Water’s default retailer (Thames Water Commercial). That tariff was rarely the cheapest then; less so now. |
| Affinity Water boundary unrecognised in contracts | Some North-West London businesses are wholesale-supplied by Affinity Water rather than Thames. A retailer offering both wholesalers may have sharper rates than your default. |
| Estimated meter readings on hard-to-access central sites | Multi-tenant buildings in the City and Canary Wharf often have meters that haven’t been physically read for 18+ months. Estimates drift upward; actual readings recover the difference. |
Can London businesses switch water supplier?
The water retailers below all supply non-household water across England. They can all supply Thames Water and Affinity Water wholesale areas. Pricing, service quality and London-sector experience vary — most operators shortlist three for a London comparison.
If you run a specific type of London business, the relevant sector-specific guide may be useful: coffee shops, pubs, hair salons, commercial landlords, warehouses and logistics, holiday lets, small businesses.
Routes to procurement
Three ways London businesses typically bring a new water contract in. Each comes with its own trade-off between control, effort and how sharp the price lands.
London business water FAQs
Who supplies wholesale water to my London business?
Most of central and Greater London is supplied wholesale by Thames Water. Parts of north-west London, areas of Hertfordshire and west Surrey are supplied by Affinity Water. Your wholesaler is determined by postcode, not by the retailer you choose. The retailer can change; the wholesaler can’t.
Can a London business switch water supplier?
Yes. Since the non-household water market opened in April 2017, every business in England can choose a different water retailer. The retailer is the company that bills you, reads your meter and handles account questions. The wholesaler (Thames Water or Affinity Water in London) still owns the pipes and the supply.
What is the Thames Tideway tunnel charge?
A pass-through charge on every Thames Water customer’s bill that funds the new sewer tunnel running under London. It’s a wholesale charge, not something your retailer sets. Different retailers display it differently on the invoice (some absorb part of it, most pass it through clearly) but the underlying rate is the same.
How much does a typical London business save by switching water supplier?
A small London business (single shop, small office, salon) typically saves £400–£900 a year. A midsize site (busy restaurant, multi-tenant office, hospitality venue) saves £900–£2,500. A large London estate or multi-site operator typically saves £3,000–£10,000 a year on the supply contract alone, before any historic refunds.
Do all water retailers cover London?
Yes. The licensed retailers can supply Thames Water and Affinity Water wholesale areas. The differences worth checking are: which retailer has a dedicated London account team, which absorbs vs passes-through Tideway, and which offers the sharpest unit rate for the volume tier your business sits in.
What is the surface water drainage charge and can London businesses claim it back?
It’s a charge for rainwater that lands on your property and enters the public sewer. London buildings frequently route rainwater to private soakaways, attenuation ponds (newer developments), or combined sewers via internal drains rather than surface drains. Where rainwater isn’t reaching the public surface drainage network, the charge can be partially or fully refunded up to six years back.
How long does a switch take in London?
Two to six weeks from contract signature. The supply doesn’t change — the wholesaler still runs the pipes and the meter. Only the retailer (your billing provider) changes. There’s no installation, no engineer visit, no service interruption.
Compare business water in another UK city
Local context, wholesaler details and switching guidance for businesses across the UK.
