Find out how many kW a battery can realistically shave off your peak demand, and how much that's worth against your demand charge.
The battery's power rating and usable energy both cap how much you can shave — whichever is smaller than your target wins.
Further reading: Solar Battery Storage 101: Sizing, Cost, and Whether It's Worth It · Battery ROI (Time-of-Use Arbitrage) Calculator
Peak shaving is using a battery to trim your single highest demand spike each billing period — typically the highest 15 to 30 minute average draw the utility records — because many commercial, industrial, and some residential rate plans bill a separate demand charge based on that one peak, on top of the normal per-kWh energy charge. Shave that one spike and the demand charge line item drops, even though your total monthly energy use barely changes.
Two things can cap how much you actually shave, independent of what you're aiming for: the battery's power rating (how fast it can discharge, in kW) and its usable energy divided by how long the peak event typically lasts (how long it can sustain that discharge, in kWh ÷ hours). A battery sized for backup runtime is often power-limited for peak shaving, while a battery sized for a quick power boost can be energy-limited if peak events run long — this calculator checks both and tells you which one binds.
Demand charges vary widely by utility and rate class — commercial rates often run $8 to $25 per kW per month, and some industrial or high-demand rates go higher. Check your own utility tariff sheet or a recent bill's demand charge line for the exact number to plug in here.
Your target reduction is a goal, not a guarantee — if the battery's power rating or its usable-energy-over-event-length is smaller than the kW your target implies, that smaller number is what the battery can actually deliver. The "limiting factor" result tells you which spec to upsize if you want to hit your original target.
No — they're two separate savings streams from the same battery. Peak shaving cuts the demand charge by trimming your one highest spike; arbitrage cuts the energy charge by shifting consumption from expensive to cheap hours. Use the Battery ROI Calculator to estimate arbitrage savings and add the two together for a fuller payback picture.
It depends on when your peak happens — solar directly reduces daytime demand spikes, but if your peak is driven by evening loads (like EV charging or AC after sunset) solar alone won't touch it and battery-based peak shaving is what actually moves the demand charge.