"How big a battery?" is the wrong first question
The most common question about energy storage is "how many kWh should I install?" — but battery size cannot be read off your factory's size or even its monthly bill. A BESS is a tool, and its right size depends entirely on what you want it to do. Get the goal clear first, and the size follows.
Two numbers, not one: power (kW) and energy (kWh)
A battery is described by two independent numbers, and confusing them is the most common sizing mistake:
- Power (kW) — how hard the battery can push at any instant. This determines how big a peak it can shave, or how much load it can back up.
- Energy (kWh) — how much it can store, which sets how long it can sustain that output.
Sizing follows the goal
| Goal | What drives the size |
|---|---|
| Peak shaving (cut Demand Charge) | The height and duration of your peaks — power to trim the peak, energy to last through it |
| Solar self-consumption | The surplus midday solar you want to store for later use |
| Backup | The critical load (kW) and how long you need to ride through (kWh) |
| TOU arbitrage | The energy you shift from Off-Peak to On-Peak, and the price spread |
The load profile decides it
The single most important input is your 15-minute load profile over a representative period. It reveals the shape and timing of your peaks, your daytime and evening use, and how solar overlaps with demand. Sizing a battery without it is guesswork; sizing it with it is engineering.
What drives the ROI
- Demand-charge savings — trimming the monthly peak, often the largest single line on an industrial bill
- TOU price spread — charging at Off-Peak and discharging at On-Peak captures the rate difference
- Higher solar self-consumption — storing surplus solar to use later, instead of exporting it cheaply
- Avoided backup — where the BESS also serves a reliability need
Don't over- or under-size
- Oversizing ties up capital in capacity you rarely use — the extra kWh sits idle
- Undersizing leaves savings on the table — a battery too small to cover the full peak still pays a demand charge
Battery life matters too
A battery's economics depend on how it is used. Depth of discharge (DoD), C-rate (how fast it charges/discharges relative to its size), and cycles per day all affect its life. LFP (Lithium Iron Phosphate) chemistry tolerates heat and heavy daily cycling well, which suits industrial duty. A good design keeps the battery within healthy limits so it lasts its intended life.
Why AI dispatch changes the maths
Two identical batteries can deliver very different returns, because value depends on how the battery is dispatched. A fixed-rule controller is cautious and leaves value unused. A forecast-driven system like GridMind AI predicts load and solar and recomputes the strategy continuously — so the same hardware captures more demand-charge savings and more arbitrage. In other words, correct sizing sets the ceiling; smart dispatch decides how close you get to it.
Where LEONICS fits
LEONICS sizes and delivers BESS (with Modular PCS) alongside Solar and GridMind AI dispatch, designed from your real 15-minute load profile — so the battery is neither too big nor too small for your goals, and it is operated to extract the value it was sized for.
Frequently asked questions
Can I size a battery from my monthly bill alone?
No. A monthly bill hides the shape of your peaks. Proper sizing needs the 15-minute load profile, which shows how high and how long the peaks are.What's the difference between kW and kWh?
kW is power — how hard the battery pushes; kWh is energy — how long it lasts. You size both: power for the peak, energy for its duration.How long does an industrial battery last?
It depends on how it is used — depth of discharge, C-rate, and cycles per day. LFP chemistry suits heavy industrial duty, and a good design keeps it within healthy limits for its rated life.Does AI really change the return?
Yes. Correct sizing sets the potential; forecast-driven dispatch decides how much of that potential is actually captured, often meaningfully more than fixed rules.Getting started
The right BESS size comes from your real load and your goals, not a rule of thumb. LEONICS offers a free Solar Insight Pro feasibility analysis that models storage size and payback from your own data.
Read the Industrial Factory solution or talk to the LEONICS engineering team.