Energy Arbitrage Calculator for TOU and Spot Markets

Where arbitrage creates value

Arbitrage works wherever the price of energy moves predictably or volatilely within the day. Under time-of-use (TOU) tariffs, the battery shifts consumption from peak to off-peak windows. Under spot exposure — for example retail plans indexed to the wholesale market — it charges in cheap intervals and discharges into price spikes.

The value is the spread minus round-trip efficiency losses and degradation. A wide, reliable spread pays; a thin one may not cover wear. The calculator makes that trade-off explicit rather than assuming every cycle is profitable.

How the calculator works

Upload your interval load and tariff (or spot price exposure). The tool schedules charge and discharge to maximise net benefit each day, respecting power and energy limits and state of charge, then totals the annual arbitrage revenue. On sites with demand charges or solar, it co-optimises arbitrage with those streams so cycles are not double-counted.

Arbitrage in Australia's spot markets

Australia has some of the most active price volatility in the region. Retail plans indexed to the National Electricity Market (for example Amber or Localvolts) expose C&I sites to wholesale spikes that a battery can capture. The tool detects spot exposure and models arbitrage against price movement rather than a fixed TOU split.

Round-trip losses and battery wear

Every stored kilowatt-hour returns slightly smaller after efficiency losses, and every cycle consumes a little battery life. The algorithm applies both, so a cycle is only scheduled when the captured spread beats its true cost — the difference between modelled revenue and the theoretical maximum a spreadsheet would show.

On sites that also shave demand or carry solar, arbitrage is co-optimised with those streams rather than counted separately, so annual revenue is not inflated by double-using the same battery capacity.

What the results include

You get annual arbitrage revenue, the number of profitable cycles, and how it stacks with demand and solar savings into one NPV / IRR / payback case — the figure you can defend in front of a client or investment committee.

Sizing for a durable spread, not a peak year

Time-of-use windows and spot volatility change over time, so a battery sized to last year's exceptional spread can disappoint. The tool's sensitivity view shows how arbitrage revenue moves if spreads narrow or widen, so you can size for a spread that holds up across years rather than betting the case on a single favourable period.

That matters most on spot exposure, where a handful of extreme events can dominate a year — the model separates the durable, repeatable value from the one-off spikes.

Realistic revenue, not a theoretical maximum

Perfect-foresight arbitrage overstates revenue. EWISER EStack dispatches against the actual profile with efficiency losses and cycle limits applied, giving a figure you can defend — and it folds arbitrage into the same report as peak shaving and solar so the combined case is coherent.

Frequently asked questions