During the operational life of a BESS, the asset must generate enough revenue to cover all investment and operational costs and deliver a net profit for investors. So, how do these highly flexible assets bring in revenue?
The Two Main Revenue Streams
1. Wholesale Energy Markets: Buying Low, Selling High
BESS assets participate in wholesale markets by charging when electricity prices are low and discharging when prices are high. This is known as arbitrage — profiting from price differences at different points in time.
When there is abundant renewable generation (and therefore cheap electricity), the BESS buys and stores. When demand is high and generation is scarce (and therefore prices are high), the BESS sells its stored electricity back to the grid.
2. Ancillary Services Markets: Providing Stability Services
These are specialised markets where grid operators (TSOs) pay for services that help maintain the stability and quality of the electricity grid — such as keeping the frequency at 50 Hz. BESS assets are highly valued in these markets due to their incredibly fast response times.
Rather than trading electricity itself, ancillary services revenue comes from being available and ready to respond instantly to TSO signals. Assets are often paid just for reserving capacity — regardless of whether they are actually activated.
Full-Stack Optimisation: Maximising Every Opportunity
The real power for BESS profitability comes from full-stack or cross-market optimisation.
Rather than being limited to one market, a well-optimised BESS simultaneously considers all available markets — wholesale and various ancillary services — in real time. It then makes instant decisions about where the battery can earn the most money at any given moment.
The market landscape shifts constantly. Prices and demand for different services change minute by minute. Full-stack optimisation ensures the BESS is always executing the most profitable strategy at that exact time, maximising overall revenue and helping to offset the significant costs of ownership.
Tolling: A Different Kind of Revenue Security
While wholesale trading and ancillary services are the active revenue streams, Tolling Agreements offer a different approach.
Tolling is not a revenue stream in its own right. Instead, it is a contract that exchanges the variable, real-time revenue earned by optimising the BESS (the floating leg) for a predictable, stable tolling fee paid to the asset owner (the fixed leg). This de-risks market exposure for investors.
Tolling and other de-risking strategies are covered in detail in Module 5. Last modified on April 20, 2026
