A commercial electricity bill can increase even when total kWh barely changes. The reason is that many business tariffs charge not only for energy used, but also for the highest demand placed on the grid, power factor, time of use, and other utility-specific components.
To understand a business electric bill, separate four ideas: kWh, kW demand, load factor, and power factor. They describe different parts of how the facility uses electricity.
1. kWh: How Much Energy You Used
Kilowatt-hours measure energy over time.
Energy = power × time
A 100 kW load operating for 10 hours uses:
100 kW × 10 h = 1,000 kWh
Energy charges are usually based on total kWh consumed during the billing period, sometimes with different rates by time of day.
To calculate billed demand from interval meter data, use the worked example in How to Calculate 15-Minute Peak Demand From kWh. Utility ratchets and tariff terms may still change the final billed kW.
2. kW Demand: Your Highest Power Level
Demand charges measure how much power the business needs at its peak, often based on the highest 15-minute or 30-minute interval during the billing month.
A facility can use the same monthly kWh but pay a higher bill if many large loads operate at the same time and create a higher peak.
| Facility | Monthly energy | Peak demand | Possible bill effect |
|---|---|---|---|
| A | 100,000 kWh | 250 kW | Lower demand charge |
| B | 100,000 kWh | 500 kW | Higher demand charge |
Both facilities used the same energy, but Facility B required twice as much instantaneous capacity at its peak.
3. Demand Ratchets: Why One Bad Month Can Affect Later Bills
Some tariffs use a demand ratchet. Instead of billing only the current month’s peak, the utility may bill a percentage of a prior peak for several future months.
For example, if a tariff uses an 80% annual ratchet and a factory reaches 1,000 kW in July, later months might be billed at no less than 800 kW even if actual demand falls below that level.
Ratchet rules vary by utility, so the exact percentage and look-back period must be checked in the tariff.
4. Power Factor: kW vs. kVA
Power factor describes how effectively apparent power is converted into real power.
Power factor = kW ÷ kVA
A facility using 400 kW at 0.80 power factor requires 500 kVA of apparent power.
400 kW ÷ 0.80 = 500 kVA
Low power factor increases current for the same real power. Some utilities apply penalties or bill demand in a way that reflects poor power factor.
Why Motors and Transformers Matter
Factories, warehouses, commercial HVAC systems, pumps, compressors, and large motors can create significant reactive power. Poorly loaded transformers and motor systems can also affect the facility’s power factor and demand profile.
Power-factor correction capacitors can help in the right application, but they should be engineered carefully. Overcorrection, harmonics, and switching conditions can create new problems.
5. Load Factor: How Evenly You Use Power
Load factor compares average demand with peak demand.
Load factor = average demand ÷ peak demand
A facility that uses 500 kW almost continuously has a high load factor. A facility that briefly spikes to 500 kW but spends most of the month near 100 kW has a low load factor.
Utilities often prefer high-load-factor customers because grid assets are used more consistently.
A Simple Commercial Bill Example
Assume a business uses 120,000 kWh in one month, has a billed demand of 400 kW, pays $0.08/kWh for energy, and $15/kW for demand.
Energy charge = 120,000 × $0.08 = $9,600
Demand charge = 400 × $15 = $6,000
Before taxes, riders, transmission, and other charges, the subtotal is already $15,600.
Now imagine the same business reduces demand from 400 kW to 300 kW without changing total kWh. The demand charge falls by $1,500 in this simplified example.
How Businesses Can Reduce Demand Charges
- Stagger large equipment starts
- Use controls to avoid simultaneous peaks
- Shift flexible loads to off-peak periods
- Use battery storage for peak shaving where economics support it
- Improve HVAC scheduling
- Monitor interval data rather than only monthly kWh
→ Related Guide: Can Battery Storage Reduce Data Center Grid Costs?
Why Solar May Not Eliminate Demand Charges
Commercial solar can reduce daytime kWh purchases, but it does not always reduce the facility’s monthly peak. If the peak occurs after sunset or during a cloudy period, the demand charge may remain almost unchanged.
That is why commercial solar economics should distinguish energy savings from demand savings.
→ Related Guide: Commercial Solar Power Installation Guide
What to Look for on the Actual Bill
- Total kWh by billing period
- Peak kW or kVA demand
- Demand-ratchet language
- Power-factor adjustment
- Time-of-use periods
- Transmission and distribution riders
- Taxes and other utility charges
Bottom Line
A commercial electricity bill is not just kWh multiplied by a rate. Energy measures how much electricity the business uses; demand measures how much capacity the business requires at its peak; power factor affects how much apparent power the electrical system must carry.
Once those pieces are separated, it becomes much easier to identify whether the best savings opportunity is reducing total energy, lowering peak demand, improving power factor, or changing when major loads operate.
About the author
I have practical experience in electrical construction and electrical project coordination in South Korea. For U.S.-focused guides, I research official codes, government data, utility documents, and manufacturer specifications to explain electrical and energy topics as accurately and practically as possible.
Sources & Official References
- U.S. Department of Energy — Industrial Energy Efficiency
- U.S. Department of Energy — Better Buildings Solution Center
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