- Only the retail margin is negotiable — the wholesale charge is fixed
- Confirm the retailer supports your billing setup (multi-site, POs)
- Switching is invisible to your day-to-day supply
- Historic debt can block a switch — clear it before you start
Wholesaler vs retailer
The wholesaler (Thames Water, Severn Trent etc.) still owns the network and sets most of the underlying charge. The retailer manages billing, meter reads, customer service and adds a margin — that margin is what you're comparing.
Where retailers actually compete
Retailers compete on retail margin, billing accuracy, meter-read frequency, consolidated multi-site billing and value-added services like leak alerts and consumption dashboards.
What to check before switching
Ask for a retail margin quote, confirm whether they'll take on any historic debt, check billing frequency and confirm they support consolidated invoicing if you run more than one site.
How switching works
You give notice, the new retailer registers your Supply Point ID (SPID) with the central market operator (MOSL), and billing transfers on the effective date. Supply itself never stops — no pipes change hands.
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