Flexibility markets explained for fleets.
A plain-English guide to how smart charging and flexible demand can create value, and the eligibility and access conditions that decide how much your fleet can actually reach.
The electricity grid has one unforgiving job: supply and demand must match, second by second. As more power comes from wind and sun, which don’t generate on command, keeping that balance gets harder. So the system increasingly does something it never used to. Rather than only paying power stations to produce more, it pays consumers to move their demand: to use less when the grid is tight, or more when there’s a surplus.
That ability to move demand has a name, flexibility, and it has a price. A depot full of plugged-in electric vehicles is close to the ideal source of it: a large, controllable load that mostly sits idle overnight, with hours of slack before anyone needs to drive. The question for a fleet is not whether the value exists. It’s which parts of it you can reach, and how.
Two different ways flexibility pays
It helps to separate two things that often get bundled together.
Spending less. This is about when you buy electricity. Shift charging out of expensive evening hours into cheap overnight windows, avoid costly network bands, flatten your peak so demand charges fall, and catch the increasingly common periods when wholesale power is very cheap or even negative. This is available to almost any depot, needs no special registration, and is the foundation everything else sits on.
Earning more. This is being paid by the grid to make your demand available, to turn down on request, or to stand ready in case you’re needed. This is the flexibility market proper. The value is higher, but so are the conditions: you have to be eligible, metered correctly, and able to reach the market, usually through a partner.
The first is a saving you control. The second is a revenue you qualify for. A strong fleet energy strategy does both.
The markets, in plain English
There are two levels at which a fleet’s flexibility can be bought: nationally, by the system operator, and locally, by the regional network.
National system operator (NESO)
Entry: 0.1 MW to 1 MW+
Demand that can turn down (or up) to balance the grid
Many national services expect substantial controllable load, more than a single mid-size depot usually offers on its own, so fleets typically reach them pooled with other assets through an aggregator, registered for the Balancing Mechanism as a Virtual Lead Party.
- Demand Flexibility Service
- Balancing Mechanism
- Capacity Market
Local networks (DSOs)
Entry: Tens of kW
Flexibility in a specific area, to avoid building new cables
Entry sizes here can be far lower, in some local markets controllable load measured in tens of kilowatts, which often puts a single depot in reach on its own.
- Local flexibility platforms
A few of these are worth knowing by name:
- The Demand Flexibility Service (DFS) is the accessible national entry point: a “use less, or increasingly use more, at these hours and get paid” scheme. It began as a winter-only service, became year-round in November 2024, and was expanded in April 2026 with a participation threshold cut to 0.1 MW, which puts a single depot in scope directly. Schemes of this kind are reshaped as the system operator’s needs change, so check the current terms before building a case on one.
- The Balancing Mechanism is the live market the operator uses to keep the grid balanced minute to minute. It has been open to independent aggregators since the P344 modification took effect in December 2019, through the Virtual Lead Party route, and P375 added asset metering in 2022 so a depot’s chargers can participate without settling the whole site. P415, approved in 2023 and live from November 2024, extends that access to the wholesale market.
- The Capacity Market pays assets to be available during periods of system stress, whether or not they’re called on, a steadier, smaller payment for standing ready.
- Local DSO flexibility is often the most practical route for a single depot. Regional networks would rather pay you to ease a local pinch point than spend millions reinforcing cables, and entry sizes here can be far lower, in some local markets, controllable load measured in tens of kilowatts.
The catch your fleet needs to understand
This is where the honest caveats live, and they’re the reason the value is “potential” until proven.
Size: Many national services expect substantial controllable load, more than a single mid-size depot usually offers on its own, though thresholds are falling: the Demand Flexibility Service now admits 0.1 MW. Where a threshold still bites, the answer is aggregation: your fleet is pooled with other assets to clear it via an aggregator.
Metering and qualification: Markets require accurate, half-hourly metering, registration, and in some cases prequalification testing. None of it is exotic, but it isn’t automatic either.
Real-world yield is lower than the headline: Not every vehicle is plugged in and sparable during every event, and the aggregator takes a cut. A realistic estimate sits well below the theoretical maximum, treat any single-number promise with caution.
It depends on you: Your region, your tariff, your duty cycles, and which markets you can reach all change the answer. The mechanism is real and growing, but the amount is specific to each fleet.
What it adds up to
The money rarely comes from one source. It comes from stacking, cheap-hour charging plus network-band savings plus one or two market services, and the combination is what turns flexibility from a rounding error into a material line. TOGL puts the modelled annual value of that stack at £1,000–£3,000 per vehicle per year for a van and light commercial depot, so what a whole site is worth depends mostly on how many vehicles it runs; for heavier vehicles, which offer far more controllable power, the per-vehicle figures are larger again.
Modelled against unmanaged charging. Around 40% of the modelled value is charging cost savings available through smart charging today; the remainder depends on demand charge reduction (in development) and flexibility revenue (planned). Indicative ranges only, subject to TOGL modelling. Actual value depends on duty cycle, battery size, tariff structure, site constraints, charging windows, integration availability, and flexibility market access.
- Charging cost savings
- 42%
- Demand charge reduction
- 28%
- Flexibility revenue
- 30%
Proportional split of modelled per-vehicle value. Illustrative and subject to TOGL modelling. The mix moves with tariff structure, site constraints and flexibility market access, which is the reason no single source is relied on.
There is one hard constraint that shapes all of it: you can only sell flexibility you can spare. A vehicle needed at 6am cannot also be turned down at 5am. So readiness comes first, and flexibility is what’s intelligently scheduled around it, never at the expense of a departure.
Where TOGL fits
The barrier for most fleets is not the existence of the value. It’s capturing it without running a full-time energy desk. Working out, vehicle by vehicle and hour by hour, what can safely be offered to which market, while handling the metering, the aggregator relationship, and the market plumbing, and never trading away a departure, is a genuinely hard optimisation problem.
That is the job TOGL is being built to do. It sits on top of the chargers and CPMS a fleet already runs, and is designed to work out what flexibility each vehicle can safely provide and when, to offer it to the markets worth reaching through an aggregator partner, and to keep the depot ready regardless.
The parts of that stack are not equally far along. Charging cost savings and demand charge reduction come from smart charging and depot load management. Flexibility market participation is planned rather than live: TOGL claims no live access to the Balancing Mechanism, national flexibility services or DSO markets, and reaching them depends on market access, asset eligibility and aggregator relationships. The aim, once that access exists, is to turn “may create value” into value that lands in the accounts.
“You can only sell flexibility you can spare. Readiness comes first, flexibility is what's intelligently scheduled around it.”
Key takeaways
- Flexibility pays in two ways: spending less (time-of-use optimisation) and earning more (grid service payments). Strong strategies do both.
- Schemes such as the Demand Flexibility Service have shown how an accessible national entry point works, but what is open changes between winters, so check the current position before building a case on one.
- The Balancing Mechanism has been open to independent aggregators through the Virtual Lead Party route since 2019, and the P415 modification, live from November 2024, extends that access to the wholesale market.
- Local DSO flexibility often has lower entry thresholds, practical for a single depot without needing aggregation.
- Value comes from stacking sources. TOGL models £1,000–£3,000 per vehicle per year for a van and light commercial depot, as an indicative range subject to modelling.
- Real-world yield sits well below the theoretical maximum, account for aggregator cut, event frequency, and asset availability.
The point
Flexibility is, in plain terms, the grid paying you to do something you can already do (charge a little later, or pause for twenty minutes) provided someone is doing the maths and you can reach the market. That single sentence holds both the opportunity and the caveat.
The fleets that capture it will treat their vehicles not just as a cost to be charged, but as an asset that earns while it waits.