How to read the number
The estimator multiplies charger power by hours in the year, your utilisation and the number of bays to get indicative energy delivered, then applies the margin between the retail price and your energy cost. It deliberately excludes grid-connection upgrades, ongoing maintenance, back-office fees and any grant or 100% first-year tax relief — all of which move the real figure. Utilisation is the sensitive input: UK chargers average around two hours' use a day, and roughly 15% is break-even while 30-35% is clearly profitable.
On a fully-funded deal you wouldn't bear the capex at all — you'd take a share of this revenue instead. Which route wins depends on your site, and a proper feasibility (with a real utilisation read and a grid check) is the only way to firm up the number.