Depot flexibility calculator
Estimate your annual benefit from TOGL
Tip: Hover over the icons for detailed explanations of each field. Download the full assumptions document above for complete methodology and data sources.
Your inputs
Prices include VAT: 20% on depot, workplace and public charging, which are business supplies, and 5% on a driver’s own domestic supply. Public and workplace rates use UK averages (Zapmap Q3 2025).
Revenue share and control depend on charger-to-vehicle integration. Where TOGL has an integration with the charger or network, DR can operate on public networks too.
Tip: depot vehicles are usually plugged in whenever they are on site, so 24/7 is the common case. Vehicles taken home overnight are typically plugged in 17:00–08:00.
Projected annual benefits (2026–2030)
Showing growth in savings and revenue as grid services expand
TOU optimisation (stable)
+50% growth by 2030
+100% growth by 2030
Estimated annual benefit
£0
Charging cost reduction
£0
(0.0%)
Flex/V2G revenue
£0
Defaults reflect published NESO and distribution network data, each dated in the assumptions document.
Figures are estimates based on your inputs and editable defaults, shown against unmanaged charging on the selected tariff. Actual outcomes vary with usage, tariffs, season and participation. This model covers charging cost savings and, where enabled, flexibility revenue; capacity and network charge reduction is assessed per site against the agreed supply capacity and is not estimated here. Figures include VAT at the applicable rate, which a VAT-registered business can normally recover on the 20% standard-rated cases.
How this works
- TOGL shifts your charging to cheaper hours based on your tariff.
- Where TOGL has an integration with your vehicle, charger or network, those assets can join grid events to earn revenue.
- Select where and when you usually plug in to refine accuracy.
- Charging cost with no flexibility£0
- Charging shifted to off-peak£0
- Demand response revenue£0
- Vehicle-to-grid revenue£0
- Net annual benefit per vehicle£0
The three middle bars each come off the flat-tariff charging cost, and together they are the net annual benefit. Figures follow your inputs above, rounded to the pound, and are estimates rather than a forecast.
Savings and revenues vary by tariff, location, and plug-in availability. Figures assume average UK grid-event prices and are based on published 2025/26 tariff data.
Assumptions
Results are calculated from representative defaults drawn from published UK data: Ofgem and DESNZ tariff statistics, NESO Demand Flexibility Service results and Zapmap charging prices, each dated in the assumptions document.
Take these numbers further
These are modelled estimates. We can run the same model against your real depot: your tariff, your vehicles and the hours they are actually plugged in.
Methodology
How this model works, and what it deliberately does not claim.
Every default below is published so the output can be checked rather than taken on trust. A fleet engineer should be able to disagree with a specific number, change it, and see what it does.
The baseline is unmanaged charging, not a flat tariff
TOGL moves load, it does not procure energy, so the counterfactual has to be the same site on the same contract charging without control. The baseline assumes 90% of energy is delivered in daytime-priced hours, which is what happens when vehicles charge on arrival.
Comparing an optimised time-of-use result against a flat daytime tariff would fold the saving from switching contract into the saving from optimisation, and overstate what the software does. If you select a flat tariff, the model says so explicitly.
Charging cost
Annual energy is distance divided by consumption. The optimised case shifts a share of that energy, 80% by default, into the overnight window at an off-peak rate of £0.10/kWh, against a blended daytime rate of £0.27/kWh and a flat SME rate of £0.25/kWh.
Those rates are 2025 UK averages against Ofgem data. The 80% shiftable share is the one to change first if your depot has tight turnarounds.
Demand response revenue
Modelled at 30 events a year, at £1.10/kWh, scaled by an availability factor of 0.8 and then again by the share of the 16:00 to 19:30 event window your vehicles are actually plugged in for. That second scaling is why the plug-in timeline matters.
£1.10/kWh sits inside published DNO utilisation ranges, and 30 events is conservative against Demand Flexibility Service dispatch in 2024/25. Frequency response services such as Dynamic Containment are priced per MW of availability rather than per kWh delivered, so they are not in this model at all.
Vehicle-to-grid, for planning only
V2G is modelled at a conservative export depth, 10% of pack for a car and 20% for an eHGV, at 85% round-trip efficiency, net of a £0.04/kWh degradation allowance and a 10% aggregator fee.
TOGL does not offer V2G today. It depends on vehicle availability, charger certification and market access, and no GB route currently pays a fleet operator a headline per-kWh export rate. The value would be realised through a supplier or aggregator arrangement. It is here so a depot can plan, not so anyone can bank it.
The projection to 2030
From a 2025 modelling baseline, demand response events grow by about 50% by 2030 as flexibility markets expand, and V2G events double as vehicle and charger capability becomes standard. Charging savings stay broadly flat.
These are assumptions about market growth, not forecasts, and they are the least certain numbers on this page.
What it does not model
Charger and installation capital cost, grid connection reinforcement, standing charges, and any saving from renegotiating agreed supply capacity. A flattened peak is the precondition for that conversation with your network operator, but the reduction is negotiated rather than automatic, so it is not counted here.
The result is a modelled annual value under stated assumptions. It is not a quote, and it is not a guarantee.
The full derivation, including every formula and source, is in the assumptions document linked above the results. Definitions of the terms used here are in the glossary, and agreed supply capacity is the one most often misread.
FAQ
About this calculator
How does the TOGL calculator work out savings?
TOGL's calculator combines the figures entered about a fleet with representative defaults for battery capacity, charging power, energy use, tariff rates and future flexibility services, drawn from published UK and EU data. The full methodology, including every default and its source, can be downloaded from the calculator page.
Are the calculator results a quote?
TOGL's calculator provides indicative planning figures, not a quote or commercial offer. Actual value depends on duty cycle, battery size, tariff structure, site limits, charging windows, supported integrations and flexibility market access.
Why does the calculator model vehicle-to-grid when TOGL does not offer it?
TOGL models vehicle-to-grid export in the calculator for planning purposes only, so a fleet can see how the case changes if V2G becomes available over the life of its vehicles. TOGL does not offer V2G today.