Compare business water suppliers
Since the Open Water market opened in 2017, any business in England can choose its water retailer. The water itself is identical, so the comparison comes down to margin, billing and service. We tender the whole retailer panel and show every cost line separately.
How to compare business water suppliers
Compare the retail layer, not the water. Your regional wholesaler is fixed by postcode and sets 80 to 95 per cent of the bill, so the difference between retailers is their margin, billing quality, multi-site consolidation and trade-effluent expertise. Put each retailer's offer side by side with the wholesale charge and the margin shown separately, then weigh the service that sits on top.
Margin transparency
Whether the wholesale charge, the retailer margin and the broker margin are shown separately, or rolled into one opaque unit rate.
Multi-site consolidation
How well the retailer handles one invoice, one renewal date and one account across several wholesale regions.
Billing and portal
Online account access, bill validation, query turnaround, and whether meter reads are automated or estimated.
Trade effluent and rebates
Mogden formula handling for industrial sites, plus surface-water and highway-drainage rebate audits.
The largest business water retailers
There are 22 licensed retailers in the English Open Water market. The five largest by supply-point volume are below. They all buy from the same regional wholesalers, so they compete on margin and service, not on the water.
| Retailer | Scale | Background |
|---|---|---|
| Business Stream | ~392k SPIDs | Wholly owned by Scottish Water; acquired Yorkshire Water Business Services on 1 October 2019. |
| Castle Water | ~199k SPIDs | Founder-led independent; acquired the Thames Water non-household book in 2017 and Brightwater on 7 February 2025. |
| Water Plus | Top 5 by volume | 50/50 joint venture between Severn Trent and United Utilities; CMA-approved May 2016. |
| Wave Utilities | Top 5 by volume | 50/50 joint venture between Anglian Water and Northumbrian Water Group; formed for the 2017 market opening. |
| Pennon Water Services | Top 5 by volume | Retail arm of FTSE-listed Pennon Group (parent of South West Water). |
Supply-point counts from the MOSL dashboard (March 2026). Not sure who bills you today? Use our free business water supplier lookup.
How to switch business water supplier
- 01
Confirm your current setup
Send us a recent water bill per site. We map every SPID, confirm your wholesale region and current retailer, and flag any trade-effluent or surface-water charges.
- 02
Compare the retail panel
We tender across the licensed Open Water retailers and present a side-by-side comparison with the wholesale charge, retailer margin and our margin shown separately.
- 03
Switch with no interruption
The retailer-to-retailer switch runs through MOSL's CMOS system with no change to your supply. We validate every invoice and alert on anomalies for the term.
Comparing business water: FAQs
How do I compare business water suppliers?
Compare the retail layer, not the wholesale charge. Your regional wholesaler (set by postcode) is fixed, so the price difference between retailers comes down to their margin, billing quality, multi-site consolidation, and trade-effluent expertise. Gather a recent bill per site, then put each retailer's offer side by side with the wholesale charge and margin shown separately. Purely Energy runs that tender for you across the whole retailer panel.
Who are the business water suppliers in England?
There are 22 licensed retailers in the English Open Water market. The five largest by supply-point volume are Business Stream, Castle Water, Water Plus, Wave Utilities and Pennon Water Services. Each buys wholesale water from the same regional wholesalers, so they compete on margin, billing and service rather than on the water itself.
Is it worth switching business water supplier?
Often yes, especially for multi-site portfolios. The retail layer is typically 5 to 15 per cent of the bill, and consolidating several sites onto one retailer with a tighter margin, plus a surface-water rebate audit, frequently pays for the switch many times over. The wholesale charge does not change, so there is no downside to your supply.
Does switching water retailer change my supply?
No. The physical wholesaler that pumps water to your site and removes wastewater never changes. Only the retailer that meters, bills, validates and serves your account changes. Outages, mains repairs and emergency response remain the wholesaler's responsibility regardless of who bills you.
Let us run the comparison for you
Send us a recent bill per site. We tender the whole Open Water retailer panel, show every margin separately, and stay with your account for the term.