BESS Sizing Tool for Commercial & Industrial Projects

What BESS sizing actually determines

Sizing a BESS means finding two numbers that fit each other and the site: the energy capacity (kWh) that stores enough to cover the target discharge window, and the power rating (kW) that is high enough to shave the demand peaks that drive your bill. Over-size either and payback stretches; under-size and you leave savings on the table.

The tool derives both from three inputs: a historical load profile (15-minute or hourly interval data), your utility tariff structure (demand charges and time-of-use energy rates), and a target — either a peak-shaving percentage or a desired payback period. It then sweeps candidate battery sizes and returns the configuration with the best risk-adjusted return.

How the tool works

Upload an interval load profile, or start from a utility bill for a preliminary estimate. EWISER EStack models battery dispatch across a full year using a reactive dispatch algorithm — the same kernel used in real deployments — rather than a simplified rule of thumb. For each candidate size it computes demand-charge reduction, energy-arbitrage revenue and, where applicable, solar self-consumption.

Results roll up into the financials that matter to an investment committee: net present value (NPV), internal rate of return (IRR), simple and discounted payback, levelised cost of energy (LCOE) and an annual cash-flow projection. Everything can be exported as an investment-ready PDF report.

The value streams it models

Peak shaving: using stored energy to cut the site's maximum demand (kW) and the monthly demand charges that follow — typically a 20–30% reduction in demand charges, which can be 30–50% of a commercial electricity bill in Asia-Pacific markets.

Energy arbitrage: charging when time-of-use energy is cheap and discharging when it is expensive, capturing the price differential under TOU tariffs or spot exposure.

Solar PV + BESS co-optimisation: jointly sizing rooftop solar and storage for maximum self-consumption and export value. Demand response and backup power are modelled as additional streams where the market and site support them.

Markets and tariffs supported

Malaysia — TNB Medium Voltage tariffs with Maximum Demand charge optimisation, and NEM 3.0 solar credits. Singapore — commercial and industrial tariff structures. Australia — National Electricity Market (NEM) regions with demand tariffs and, in New South Wales, Peak Demand Reduction Scheme (PRC) incentives. The engine applies the local tariff logic and currency for each market.

Why dispatch modelling beats a rule of thumb

A common shortcut sizes a battery from average demand or a fixed multiple of peak load. That ignores when the peaks occur, how long they last, and how they overlap with time-of-use pricing — the very things that decide whether a battery pays back. Two sites with identical peak demand can need very different systems once you look at the shape of their load over the day.

By simulating charge and discharge against your actual interval data for every hour of a representative year, EWISER EStack captures those dynamics. The result is a size that holds up under scrutiny: you can see the demand-charge reduction month by month, the arbitrage captured under your tariff, and how sensitive the payback is to battery cost and electricity prices.

From sizing to a bankable proposal

Sizing is the first step. Once a configuration clears your hurdle, EWISER EStack produces an investment-ready report — system specification, savings breakdown by value stream, capital cost, and the full NPV / IRR / payback case — that you can put in front of a client or an investment committee. For full project delivery, quoting and contracting, the analysis carries over into the EWISER partner platform.

Who it is for

Energy engineers and consultants scoping a storage project; project developers and EPC contractors preparing proposals; and C&I facility managers who need a credible, defensible number before committing capital. If you can supply a load profile or a recent bill, you can size a system in minutes.

Frequently asked questions