Commercial battery storage arbitrage in Mauritius and the Indian Ocean: what actually earns
Short answer: in Mauritius and most Indian Ocean islands there is no open wholesale spot market to arbitrage against, so a commercial battery earns from your own tariff and load — peak shaving, self-consumption shifting and demand-charge reduction — not from buying and reselling power. True price-spread arbitrage of the European kind needs a half-hourly market price; where that price does not exist, the equivalent value comes from the utility tariff structure and from grid-service contracts.
Classic arbitrage means charging when the market price is low and discharging when it is high, settling against a public spot price such as EPEX SPOT ID1/ID3 in Europe — that is the mechanism behind the figures quoted for German fleets. In Mauritius and comparable Indian Ocean island systems, generation and supply run through a single vertically integrated utility, and a commercial customer buys at a published tariff rather than at an hourly clearing price. So there is no price series for a private battery to trade against. What you can arbitrage is the difference between tariff periods and between grid import and your own solar — economically the same charge-low/discharge-high logic, but settled on your invoice instead of an exchange.
1) Demand-charge reduction: on commercial and industrial tariffs the maximum demand (kVA/kW) component is often the largest controllable line on the bill, and a battery that shaves the few 15- or 30-minute peaks per month cuts it directly. 2) Time-of-use shifting: charge in the off-peak window, discharge into the peak window; the earnings are simply (peak rate − off-peak rate) × kWh cycled, minus round-trip losses. 3) Solar self-consumption: store midday PV that would otherwise be exported at a low or capped rate and use it in the evening at the full import rate. 4) Backup value: on islands where outages during cyclone season are a real operational cost, avoided downtime is often worth more than points 1–3 combined for process industries, hotels and cold chains. Check your own tariff schedule and the last 12 months of half-hourly meter data before assuming any of these — the ranking differs per site.
Take 12 months of interval meter data. For demand charges: find the monthly maximum demand, count how many intervals sit above the level you could realistically hold, and multiply the reduction by the kVA charge — that gives an annual figure with no assumptions about future prices. For time-of-use: for each day compute the energy you could move from peak to off-peak, cap it by usable battery capacity and by C-rate, multiply by the rate difference, and apply a round-trip efficiency of roughly 85–90 % at the AC terminals for a lithium system with an inverter. Then subtract degradation: every cycle you add for a few cents of spread costs you warranty throughput. If a strategy does not clear the cost of the cycles it consumes, it is not revenue — it is capacity spent.
Cooling decides a battery's life — and its safety — in a hot climate. A grid-scale or commercial battery is a chemical asset, and in the heat and humidity of the Indian Ocean the way it is cooled is the single biggest factor in how long it lasts. This bears directly on arbitrage economics: cycling hard in ambient conditions that keep cells warm accelerates capacity fade, so a system that looks profitable on a European degradation curve can under-deliver here. Specify liquid cooling or a properly rated HVAC design, budget the parasitic cooling load as a real cost against the spread you capture, and treat any vendor cycle-life number that is not stated at your actual site temperature as unproven.
Island grids that lean on imported fuel for evening peak generation have a much larger gap between cheap solar hours and expensive peak hours than an interconnected mainland market — as solar floods the grid at noon and vanishes by evening. That gap is the physical basis of the value, whether or not it is expressed as a market price today. It also means the utility itself is the natural counterparty: grid-scale storage and ancillary services procured under contract, rather than merchant trading, are how that value is currently monetised in the region. For a commercial site, the practical route is a behind-the-meter battery on tariff optimisation now, structured so it can also bid into a grid-service or flexibility scheme if one opens.
Confirm your exact tariff category and whether it carries a maximum-demand charge and time-of-use periods — this determines whether a battery has anything to arbitrage at all. Confirm the utility's connection and grid-code requirements for storage, including export rules, since a battery that may not export is limited to self-consumption and peak shaving. Get your interval data rather than monthly bills; monthly totals hide the peaks that carry the money. Specify the thermal design against real site ambient conditions, not a datasheet default. And size the system to the load pattern you measured, not to a headline capacity — an oversized battery in a market without a spot price simply sits idle.
Charge Director
Automixer
BESS Engineer
PV Watcher