Technologies
Vehicle-to-grid (V2G) lets a parked electric vehicle export energy from its battery back to a building or the grid, earning from price spreads and flexibility markets between trips. Gridcog models V2G chargers alongside smart charging, against each vehicle's schedule, so you can compare the cashflows of simple charging and V2G for fleets, car parks and homes.
Gridcog Senior Energy Analyst Ashok Willis modelled the Octopus x BYD Dolphin V2G scheme. He estimated Octopus could make £526 to £1,015 per vehicle per year, depending on market exposure.
In a Gridcog model of an eight-truck depot in Australia, smart charging cut energy supply costs by over 63% compared with impatient charging. V2G adds discharging on top.
Gridcog Senior Energy Analyst Catalina Villaro compared 10 smart chargers with 10 V2G chargers, all 7 kW, at a long-stay car park in Australia. Predictable stays suit energy arbitrage.
Vehicle-to-grid (V2G) uses the energy stored in an electric vehicle's battery for something other than driving: exporting it to the grid through the site the vehicle is plugged into. The vehicle charges when prices are low and discharges when they're high, within the limits of its driving schedule.
A bi-directional charger lets energy flow both ways between the vehicle and the site. An optimiser, such as an energy supplier or aggregator, decides when each vehicle charges or discharges, using price signals and the charge the driver needs for the next trip. Aggregated, many vehicles can provide grid flexibility and trade in energy markets.
| Term | Where the vehicle's energy goes |
|---|---|
| Vehicle-to-grid (V2G) | Exported to the grid through the site's connection |
| Vehicle-to-building (V2B) | Used by the building or depot the vehicle is plugged into, cutting its grid imports |
| Vehicle-to-home (V2H) | Used by the home's own load rather than exported |
| Vehicle-to-everything (V2X) | The umbrella term for all of these |
V2G builds on smart charging. Smart charging changes when a vehicle charges; V2G also lets it discharge. Gridcog runs all three charging modes on the same fleet and schedule, so you can compare their cashflows.
| Charging mode | What it does | Where the value comes from |
|---|---|---|
| Impatient charging | Charges each vehicle to full as soon as it plugs in | The baseline: no optimisation |
| Smart charging | Moves charging into the cheapest periods the vehicle's schedule allows | Lower energy supply and network costs |
| Bi-directional (V2G) charging | Smart charging, plus discharging to the site or the grid | Lower costs, plus revenue from price spreads and flexibility markets |
As part of the site, interval by interval. Each vehicle's schedule, the chargers, the grid connection, tariffs and markets sit in one simulation, and Gridcog co-optimises when every vehicle charges and discharges.
Enter each vehicle's daily energy use, battery capacity, maximum charge power and an hourly schedule of when it's plugged in, or upload them from the Excel template for larger fleets. Gridcog only charges and discharges a vehicle while it's plugged in, and you can set a minimum state of charge for V2G.
Set charger size, number of chargers and a maximum demand across all of them. Then turn on bi-directional charging so vehicles can discharge to the site (V2B) or the grid (V2G). Charger capex and opex come from rate cards, so V2G hardware costs sit in the cashflows.
Value V2G against retail and network tariffs and wholesale prices, with trading across day-ahead and intraday markets, and balancing, capacity and frequency response markets where the market allows it.
Model V2G with on-site solar, a stationary battery, the site's existing load and its import and export limits. You'll see what the connection allows before you ask the network operator for more capacity.
Add the fleet operator, charge point operator, supplier or aggregator as stakeholders, split the value between them, and set which one each flexible asset optimises for.
Compare cashflows and net present value (NPV) for impatient charging, smart charging and V2G, with interval-level charging and discharging profiles.
Modelled in Gridcog
£526 to £1,015 a year, depending on market exposure, in Gridcog Senior Energy Analyst Ashok Willis's model of the Octopus x BYD Dolphin V2G scheme in Great Britain. That excludes the wider portfolio benefit to Octopus, which he describes as likely to be material.
On days with small price spreads, the car followed its driving pattern and didn't trade. On days with big spreads, it charged and discharged as fast as the charger allowed.
Ashok Willis
Senior Energy Analyst
Read Ashok's analysis of the Octopus x BYD Dolphin V2G scheme
One V2G-enabled BYD Dolphin, Great Britain
Planning V2G for a fleet, car park or customer base?
Model V2G in GridcogSites where vehicles stay plugged in for long, predictable periods. Gridcog's analysts have modelled V2G at car parks, fleet depots and homes.
Catalina Villaro modelled a long-stay car park in Australia with 10 cars, comparing smart chargers with V2G chargers at 7 kW each. The V2G site had up to 70 kW of import and export, subject to connection approval. Predictable stays suit energy arbitrage, but charger costs could move the breakeven point. Operators could offer free parking or an incentive payment to drivers who join.
Catalina Villaro
Senior Energy Analyst
Pete Tickler modelled eight electric refuse trucks, each with a 300 kWh battery, on five 100 kW chargers and a 500 kW connection at depots on Australia's east coast. Smart charging cut energy supply costs by over 63%, and V2G discharged the trucks when it improved the financials, while keeping enough charge for the next shift.
Pete Tickler
Chief Product Officer
Ashok Willis's model of the Octopus x BYD Dolphin scheme covers a single car at home, plugged in overnight on weekdays. In Ashok's model, the car's flexibility is traded in wholesale and balancing markets.
Ashok Willis
Senior Energy Analyst
Shell's e-mobility team used Gridcog to model hundreds of forecourt scenarios with fast chargers and battery storage, and to explore how fleets could contribute to the bottom line through vehicle-to-grid.
Fleet operators and charge point operators, large energy users with vehicles on site, and the energy majors and suppliers that trade their flexibility.
Request a live demo
Request a demo and we'll show you how Gridcog values V2G for your fleet or site.
The team behind Gridcog
Fabian Le Gay Brereton
Chief Executive Officer & Co-Founder
Previously co-founded Greensense, acquired by ERM Power (now Shell Energy).
Pete Tickler
Chief Product Officer & Co-Founder
Co-founded Greensense and led digital innovation at ERM Power (now Shell Energy).
Genna Boyle
Chief Commercial Officer & Head of EMEA
More than 10 years in energy strategy, trading and renewables, with senior roles at Battery Optimiser and Limejump.
.png)
