Commercial Solar Reality : EV Charging, Solar Integration, and the Tariff Trap

The Trap

The most financially costly mistake we currently see in solar and EV integration is not a technical failure. It is a tariff decision made by default.

A site installs solar. A vehicle goes electric. Someone connects them — direct daytime charging from the panels. It looks efficient. The meter is not spinning. Nobody checks whether it is actually the best approach financially.

It frequently is not.

From 1 April 2026, the Intelligent Octopus Go overnight rate sits at 8p/kWh. The standard variable tariff under the Ofgem price cap is 24.67p/kWh. Octopusreferral If your solar export rate sits above 8p/kWh — which many Smart Export Guarantee arrangements do — then exporting during the day and buying back overnight at 8p is, in many cases, financially superior to direct self-consumption for EV charging.

Nobody who sold you the panels told you to do this. Not because it is wrong advice — but because the tariff landscape has moved, and the hardware conversation usually happens before the tariff conversation.

The tariff conversation should come first.

---

What the Correct Analysis Looks Like

Scenario	Cost per kWh	Best for
Standard tariff, daytime solar direct charge	"Free" but opportunity cost applies	Simplicity, not savings
Standard tariff, no solar	24.67p/kWh	No EV strategy at all
Smart TOU tariff, overnight EV charge	8p/kWh (or under 4p in some regions)	Most households and small operators
On-site solar + TOU tariff, optimised	4–8p/kWh blended effective rate	Fleet operators, commercial sites
On-site solar + BESS + TOU tariff	5–10p/kWh (combined capital cost)	High demand, multi-vehicle sites

The question is not "which of these is cheapest in isolation." It is which combination fits your specific load profile, export arrangement, and capital position.

---

Three Things to Sort Before Commissioning Any Hardware

1. Get onto the right tariff before specifying the charger. The charger specification depends on when you will be charging. When you will be charging depends on your tariff. If you commission chargers on a standard tariff and then switch to a smart TOU tariff later, you may find your infrastructure is not optimised for the overnight window you are now trying to use.

2. Model the full load — including where the fleet is going, not just where it is today. The most common sizing mistake is building for the current vehicle count. A system sized for two EVs today that needs to handle six in three years will be drawing heavily from the grid within the planning horizon of the original capital decision. Size for the fleet projection, not the fleet today.

3. Design the charging layout for the people using it — from the start. EV charging accessibility is consistently treated as an afterthought. Bay position, surface quality, cable reach, signage, height of connection points — all of these affect whether disabled staff and customers can actually use the infrastructure you are installing. Retrofitting accessibility costs more than building it in. And for any operator with a duty of care, getting this wrong is not just an inconvenience.

---

On Grid Timelines: Manage Expectations Early

If your project involves any grid upgrade, meter change, DNO notification, or export arrangement, build more time into your programme than your installer suggests.

Grid-related processes at distribution level are not as congested as the national transmission queue — but they are not instant. Smart meter installation, export meter changes, TOU tariff eligibility confirmation — each step has a queue. Starting the process after the hardware is installed adds delay and, in some cases, means operating on a suboptimal tariff while you wait.

Start the grid and tariff conversations before the hardware conversations. It is a simple sequence change that saves real time and money.

---

What ISC Does

We run independent consultations for operators, fleet managers, and site decision-makers who need the analysis done properly before committing capital.

We have no solar panels to sell. No chargers on commission. No vendor relationships of any kind.

We look at your numbers, your site, your fleet projection, your tariff options, and your grid position — and we tell you what the evidence says.

→ Book a Consultation

---