Quick answer
Peak Shaving is discharging a battery, or cutting load, during the moments a building draws the most power from the grid, so the highest kilowatt reading in the billing period comes out lower.
It matters on electricity rates with a demand charge, which bills that single highest reading in dollars per kW on top of the energy you use.
Quick facts
The key facts about peak shaving, with sources:
- Targets
- Peak demand in kW, not energy in kWh
- Pays on
- Rates with a demand charge (capacity charge) 3
- Battery size that pays best
- Small, short-duration batteries, shaving short spikes 1
- NREL’s screening level
- Demand charges of $15/kW or more flag battery potential 2
- Also called
- Battery demand management, demand charge reduction 4
- Not the same as
- Energy arbitrage, which targets price per kWh
Key takeaways
- Peak shaving lowers the single highest kW reading on your bill.
- It saves money only on rates with a demand charge, which are mostly business rates.
- Standard South Carolina home rates we checked have no demand charge, so there is nothing to shave 8.
- Small, short batteries that catch brief spikes tend to pay best 1.
- One missed spike can set the charge for the whole month, so controls must be reliable.
What a demand charge is
Most home bills charge for energy: kilowatt-hours used over the month. Some rates, mostly for businesses, add a second part. EIA's glossary describes this two-part pricing: an energy charge, plus a capacity or demand charge assessed on the amount of capacity being used.
In practice the demand charge looks at the highest average kW drawn over a short interval set in the tariff, then bills that number for the whole month. One short burst when the HVAC, an oven and an EV charger all run can set the charge for 30 days.
A kW is a rate of use, like speed. A kWh is an amount, like distance. Peak shaving is about the top speed, not the distance. See kilowatt.
Sources: [3]
What happens during a spike
- Big loads switch on together → grid draw climbs toward the ceiling
- Controller sees it → battery discharges
- Grid draw stays at the ceiling → meter records a lower peak
- Spike ends → battery recharges from solar or off-peak power
How a battery system does it
- A meter or current sensors watch the building's draw from the grid in real time.
- The controller holds a target ceiling in kW, set from the bill history.
- When the draw approaches the ceiling, the battery discharges just enough to hold it there.
- Between spikes, the battery recharges, from solar or off-peak power.
Sandia's storage handbook describes this as the energy management system working to "shift and shave" a customer's usage within the battery's limits on capacity, efficiency and charge rate 4.
Types of peak shaving
| Type | How it lowers the peak | Best for |
|---|---|---|
| Battery peak shaving | Battery covers the spike | Short, sharp spikes |
| Load control | Delays or cycles some equipment | Flexible loads like water heaters or EV chargers |
| Solar-assisted | Solar output lowers daytime draw | Daytime peaks on clear days; unreliable alone |
| Utility-scale | Utility battery lowers the utility’s own peak | Utilities facing capacity or transmission charges 5 |
Worked example in kilowatts
An illustration of the mechanism, in kW only. The load figures are assumptions; the dollar value depends on your own tariff's $/kW demand rate.
| Without the battery | With peak shaving | |
|---|---|---|
| Usual load most of the month (assumed) | 6 kW | 6 kW |
| Short spike when big loads coincide (assumed) | 9 kW | 9 kW from the building |
| Battery discharge during the spike | 0 kW | 3 kW, within one IQ Battery 5P's 3.84 kVA 6 |
| Peak the meter records | 9 kW | 6 kW |
| Billed demand | 9 kW × your $/kW rate | 6 kW × your $/kW rate: 3 kW less |
The battery only needed enough energy to cover the spike, not the whole evening. That is why NREL found small, short-duration batteries the most cost-effective for demand-charge reduction, shaving short load spikes of about 2.5% of peak demand 1.
Example with a real tariff: Duke Energy Carolinas Schedule SGS (South Carolina)
Schedule SGS (small general service, effective 1 March 2026) bills no demand charge on the first 30 kW and $4.93 per kW above that 7. Take a small business with a 45 kW monthly peak (assumed).
| Case | Math | Monthly demand charge |
|---|---|---|
| No battery, peak 45 kW | (45 − 30) × $4.93 | $73.95 |
| Battery shaves the peak to 40 kW | (40 − 30) × $4.93 | $49.30 |
| Saving | $73.95 − $49.30 | $24.65 a month |
One catch: SGS billing demand can also be set by a ratchet, 50% of the highest peak in the past 12 months 7.
At these numbers that floor (22.5 kW) sits inside the free block, but a large spike can raise it.
And the demand rate here is below the $15/kW level NREL used to flag strong battery markets 2, so the saving alone may not pay for a battery.
Where you see your peak
- On a business bill, as “billing demand,” “kW demand” or “maximum demand.”
- On the rate schedule, which names the demand interval and price per kW.
- In interval data from a smart meter, often in the utility’s online account.
- In the battery app, as a “peak” or “demand limit” setting.
Where peak shaving fits, and where it does not
Good fit
- Businesses, farms and buildings on a rate with a demand charge.
- Load profiles with short, predictable spikes (equipment start-ups, EV chargers).
- Sites already adding storage for backup or solar self-use, so the battery does two jobs.
Poor fit
- Homes on rates with no demand charge: there is nothing to shave.
- Long, flat peaks, which need a battery large enough to cover hours, not minutes.
- Systems where one missed spike resets the month: control must be reliable.
Limits to watch
A demand charge is set by one interval. If the battery is empty, offline or slow to react for that one interval, the month’s saving is gone.
Ratchets add risk. Under a ratchet, a past peak sets a floor for future months. On Duke’s SGS that floor is 50% of the 12-month peak 7. A single unshaved spike can echo for a year.
Solar alone is not reliable for this. A cloud during your peak interval can wipe out the saving for the month.
Sources: [7]
Cost drivers and battery life
The saving is simple: kW shaved times your $/kW rate, each month. The cost side is the battery’s price, its install, and its life. Two specs drive the size: the power rating in kW must cover the spike, and the capacity in kWh must last as long as it does. See battery power rating.
Short spikes need little kWh, which keeps cost down. Long peaks need a much bigger battery. Life is set by the warranty, often in years and sometimes in cycles or energy delivered. Read it before you count on savings.
We do not print battery prices. For business systems, see commercial solar and storage.
How a peak-shaving project is set up
- Get 12 months of bills and, if possible, 15-minute interval data from the utility.
- Find the size, length and timing of the peaks.
- A licensed installer sizes the battery in kW and kWh to cover them.
- The installer pulls permits; the system is inspected and approved by the utility.
- The controller is set with a demand target, then tuned after the first bills.
Keeping it working
- Check each bill’s demand line against the target.
- Adjust the target when you add equipment or change hours.
- Keep monitoring online; a dropped connection can mean a missed spike.
- Have the installer service the system on the schedule in the warranty.
Warning signs
- A home battery is sold on demand-charge savings, but your rate has no demand charge.
- The proposal uses no interval data, only monthly totals.
- A month’s bill shows a demand spike the battery should have caught. Call the installer.
- Battery alarms or overheating. Do not open the unit; call a licensed installer.
Rules that apply
No federal rule governs peak shaving. Your utility’s rate schedule sets the demand interval, the price per kW and any ratchet. For example, Duke Energy Carolinas’ Schedule SGS in South Carolina took effect on 1 March 2026 under Docket No. 2025-172-E 7.
The battery itself must meet local building, electrical and fire codes, and is permitted and inspected like any other battery job. Energy storage systems are commonly listed to UL 9540; UL Standards & Engagement published its third edition on 28 June 2023 9. Your building department decides which listing it accepts.
Peak shaving vs energy arbitrage
| Peak shaving | Energy arbitrage | |
|---|---|---|
| Targets | Highest kW in the billing period | Price per kWh by hour |
| Rate needed | A demand charge | Time-of-use or low export credit |
| Battery runs | Only during spikes | Every peak window |
| Typical users | Businesses, farms | Homes and businesses on time-of-use |
Common misconceptions
- Myth Any home battery cuts demand charges.
- Reality Only if your rate has a demand charge. Most home rates do not.
- Myth A bigger battery always saves more.
- Reality Short spikes need little kWh; extra capacity adds cost without adding savings.
- Myth Solar panels shave peaks on their own.
- Reality Clouds make them unreliable for a one-interval charge.
Demand charges in South Carolina, Georgia and Virginia
The standard residential schedules held in our South Carolina fact file (Duke Energy Carolinas RS and R-STOU, Dominion Energy South Carolina Rate 8 and Rate 5) bill energy and a fixed charge, not a demand charge 8.
Demand charges in the state show up on business schedules such as Duke's SGS (effective 1 March 2026) 7. We have not verified Georgia or Virginia demand tariffs; check your utility’s current business schedule.
Is peak shaving for you?
First check your rate schedule. No demand charge, no peak shaving value. Look instead at arbitrage or backup.
If you do have a demand charge, multiply the kW you could shave by the $/kW rate, then by 12. Compare that yearly figure with the battery’s cost over its warranted life.
Next step: pull your interval data and talk to a commercial installer. See battery storage services.
Related
Questions about peak shaving
What is the difference between peak shaving and load shifting?
Peak shaving lowers the single highest kW reading to cut a demand charge. Load shifting, or energy arbitrage, moves kWh from expensive hours to cheap ones. One battery can do both if its controls allow. Which one pays depends on whether your rate has a demand charge, a time-of-use price gap, or both.
Do residential electricity rates have demand charges?
Most do not. Demand charges are mainly on commercial and industrial rates. The standard South Carolina home schedules we checked bill energy and a fixed charge only. Some utilities elsewhere offer residential demand rates, so check the rate schedule printed on your bill.
How big a battery do I need for peak shaving?
Big enough in kW to cover the spike, and in kWh to last as long as it does. NREL found small, short-duration batteries the most cost-effective for this job. Interval data from your utility shows how high and how long your spikes are.
Can solar alone shave peaks?
Only when the sun cooperates. A cloud during your peak interval can wipe out the saving for the month. That is why demand-charge savings are usually credited to the battery, not the panels. Solar plus a battery is more reliable.
How much can peak shaving save?
The kW you shave times your demand rate, each month. On Duke Energy Carolinas’ Schedule SGS in South Carolina, shaving a 45 kW peak to 40 kW saves 5 × $4.93, or $24.65 a month. Higher demand rates save more. NREL used $15 per kW as a level that flags strong battery potential.
What is a demand ratchet?
A ratchet sets a minimum billing demand based on an earlier peak. On Duke’s SGS, billing demand can be 50% of the highest peak in the past 12 months. So one unshaved spike can keep your demand charge higher for up to a year.
Does peak shaving help the grid?
Yes. Lower peaks mean less strain at the busiest times. Utilities use batteries for the same reason. NREL describes a Vermont utility using a 4 MW battery to cut its own capacity and transmission demand charges.
Can I peak-shave with smart controls instead of a battery?
Sometimes. Load control delays or cycles flexible equipment, such as water heaters or EV chargers, during spikes. It costs less than a battery but only works if those loads can wait. Many sites combine both.
Sources
- Neubauer and Simpson, Deployment of Behind-the-Meter Energy Storage for Demand Charge Reduction (NREL/TP-5400-63162, January 2015), via OSTI, retrieved .
- McLaren, Gagnon and Mullendore, NREL/Clean Energy Group, Identifying Potential Markets for Behind-the-Meter Battery Energy Storage: A Survey of U.S. Demand Charges (NREL/BR-6A20-68963, Aug 2017), retrieved .
- US EIA, Glossary: Demand charge / capacity charge, retrieved .
- Sandia National Laboratories, DOE/EPRI Energy Storage Handbook, Chapter 15: Energy Storage Management Systems, retrieved .
- NREL, Grid-Scale Battery Storage: Frequently Asked Questions (NREL/TP-6A20-74426, 2019), retrieved .
- Enphase Energy, IQ Battery 5P data sheet (DSH-00010-11.0-EN-2025-05-06), retrieved .
- Duke Energy Carolinas (SC), Schedule SGS Small General Service, effective 1 March 2026 (Docket No. 2025-172-E, Order No. 2025-769), retrieved .
- Duke Energy Carolinas (SC), Schedule RS (Docket No. 2025-172-E), retrieved .
- UL Standards & Engagement, ULSE publishes third edition of UL 9540, Energy Storage Systems and Equipment (28 June 2023), retrieved .
Expert review
Written by the HyreSolar Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: Demand-charge definition from EIA; cost-effectiveness findings from the NREL reports via OSTI; control description from Sandia; utility case from NREL's FAQ.
SGS figures reuse the Duke tariff read for our demand charge entry on 8 October 2026. The first worked example uses labelled kW assumptions; the second multiplies published SGS rates by an assumed peak.
Suggest a correction. We fix errors and say what changed.