Clear answer, explained.
Battery storage systems are sized against the facility's demand profile — the pattern of when and how much electricity the building draws from the grid, and specifically the peak windows that determine the monthly demand charge. Unlike solar, which is sized against annual consumption, storage is sized against the shape and duration of demand peaks: how high the peak is, how long it lasts, and how frequently it occurs across billing periods.
A facility where demand spikes are brief — a single piece of equipment starting momentarily — may achieve meaningful demand charge reduction with a relatively small system. A facility with sustained high-demand windows — continuous process loads, large HVAC systems, or refrigeration running simultaneously — requires a system with enough capacity to discharge across that full window. Over-sizing storage wastes capital; under-sizing leaves demand charge savings on the table.
The demand analysis in the assessment phase uses 15-minute interval data to characterise the facility's demand profile in detail, identify the peaks driving the highest monthly charges, and model the storage system configuration that addresses those peaks most cost-effectively. This analysis is completed before any equipment is specified or priced — ensuring the system is right-sized for the financial return, not defaulted to a round number.
What this means in practice.
- Storage is sized against the facility's demand profile — the size and duration of peaks driving monthly demand charges
- A facility with brief demand spikes may need only a small system to achieve meaningful demand charge reduction
- A facility with sustained high-demand windows requires more capacity to discharge across the full peak window
- Over-sizing storage wastes capital; under-sizing leaves demand charge savings unrealised
- 15-minute interval data is the input for demand profile analysis — identifying which peaks drive the highest monthly charges
- System size is determined in the assessment phase before any equipment is specified or priced
Best-fit environments.
- You want to understand how battery storage is sized before requesting a proposal
- Your electricity bill has high demand charges and you want to know whether a small or large system is appropriate
- You are building a capital budget and need a preliminary sense of system size before commissioning a full assessment
- You want to understand whether your facility's demand profile is well-suited to battery storage before investing in analysis
