InsightsPractice
PracticeP003Energy & Fleet OperationsBy Fabrice Macarty · Maxime Ferrand

A fleet battery earns what the contract leaves it

Vehicle-to-grid tariffs are on sale, and the revenue quoted to a fleet can be gross: before the aggregator’s share, before battery wear. Four contract clauses, from net ledger to downside case, turn a fleet battery into a number a CFO can approve.

$9,741/yr
upper bound of PJM Regulation revenue for a 33 kW fleet vehicle, from measured pilot performance and 2021 to 2025 prices, net of energy losses and before aggregator fees, customer support and battery wear (UD / Exelon report, March 2026, page 4).
€132/MWh
compensation a vehicle owner needs per MWh of V2G energy flow to break even on battery degradation and infrastructure cost in the 2030 scenario (Sagaria, van der Kam and Boström, Applied Energy, 2025).
Finance & RiskAutomotive & MobilityEnergy, Utilities & Grid
The decision stakes

From quoted revenue
to retained value.

Something that might not be obvious to everyone is that these payments are not a subsidy; these EVs are earning money by competing with legacy generators, which is novel in a lot of ways.Prof. Willett Kempton, University of Delaware, 16 April 2026

The net return on a fleet battery is the market payment less three deductions: the energy lost on the round trip, priced at the tariff the fleet pays to recharge; the aggregator’s retained share; and a provision for wear. The battery sets how much energy is lost and how fast the cells age; the contract sets what each costs the fleet and the limits within which the battery runs.

Energy returned to the grid is measured at the meter, so an external party can audit it, and the same reading can serve the P&L and the sustainability report once the two are reconciled. Any environmental benefit claimed from it needs its own method.

The decision tool

Four clauses
before signature.

01

Net Ledger

Identify the contract model, direct utility or aggregator, and obtain each price in writing: the payment per hour of availability, the payment per kWh discharged and, for an aggregator, the share of market revenue it keeps and the fees it passes through. Plan on the 90% round-trip efficiency the UD / Exelon report assumes, and stress the model at 80%, a floor this case sets against the 16 to 25% losses the meters recorded. Show the CFO the net figure.

A direct utility tariff publishes what the fleet receives, not the value earned from the underlying grid services. The spread cannot be established from the published tariff alone.
02

Soc Covenant

Write the state-of-charge window into the agreement, aligned with the carmaker’s recommendation for the model. Without V2G, calendar ageing accounts for 85 to 90% of ten-year degradation; V2G adds an average 0.31% a year to total degradation in a modelled scenario of 33 charging and discharging cycles (Sagaria et al., 2025). None of the four Delaware vehicles showed measurable degradation on its carmaker’s state-of-health reading, the report states (page 23); the cars covered 1 to 2% of the mileage of the fleet’s other vehicles. Renault states that its battery keeps the same warranty whether or not the owner uses its V2G service.

An explicit state-of-charge window makes the operating limits verifiable; leaving them to the dispatch algorithm may create uncertainty over warranty compliance. Ask the carmaker to confirm the window in writing for the model.
03

Throughput Envelope

Specify a megawatt-hour throughput envelope in the vehicle tender and in the V2G service agreement: a guaranteed minimum, paid at a rate written alongside it, and a contractual maximum, agreed with the carmaker against its warranty terms. In 2025, the four Delaware vehicles discharged three to five times the energy a typical 11,000-mile driving year would need, the report calculates (page 23).

A fleet that requires the envelope in its tender obliges its suppliers to produce it, and a clause repeated across several tenders can become a market standard. Bonuses tied to connected hours are already published in Germany by BMW, Mercedes-Benz and Ford with their energy partners; the throughput ceiling is the next figure to ask for in writing.
04

Downside Case

Run the downside before the base case: Regulation at the low year of the series, $21 per MW-hour against $55 at the high (page 4); availability set at the fleet’s own driving hours, where the report’s figures already assume eight a working day (pages 4 and 15); the aggregator’s share at the ceiling written into the contract; efficiency at the 80% floor; degradation and infrastructure provisioned together at the €132/MWh break-even of the 2030 scenario (Sagaria et al., 2025), with no separate wear line. The programme is signable when the downside still covers its cost of capital.

The downside number is the one a CFO can approve as a capital decision, outside the fleet operations budget. It also fixes the rank of the service. Mobility comes first: any dispatch provision that could compromise a scheduled trip should be treated as an operational constraint and assessed in the downside case.
The proof

BMW / E.ON

Germany’s first bidirectional charging tariff for private customers, in the words of its sellers, on sale since 9 February 2026; among the most complete public price lists available for benchmarking.

€720/yr

BMW Group sets the availability bonus at 24 cents per connected hour, capped at €60 a month and €720 a year, paid whether energy is charged or discharged; a second stream pays 40 cents per kWh discharged (press release, 9 February 2026).

The product is sold to private owners of the iX3, and its interest for a fleet lies in its architecture. Stream one pays for availability, €720 a year on 250 hours of connection a month, earned whether or not a single kWh moves; stream two pays for energy, 40 cents per kWh discharged, BMW states. A footnote in the release converts the bonus into 2,184 kWh of charging at an average 32.97 cents, about 12,000 to 14,000 km a year; a fleet models the euros credited. Read as a contract, the tariff discloses the unit of payment, the cap and the assumption behind the headline; the algorithm, developed jointly by BMW and E.ON, keeps the battery ‘within an optimal operating range’, BMW states, while the driver sets the charge targets. E.ON pays fixed prices; the release does not say what the pooled grid services earn, so the spread cannot be read from the tariff.

BMW and E.ON published the unit, the cap and the assumption behind their headline. A fleet negotiating with an aggregator can ask for the same disclosure, with the retained share added to the list.

The full case

PDF · 5 slides