Example Data Table
| Scenario | Monthly kWh | Peak % | Peak Rate | Off-Peak Rate | Shiftable kWh | Shift % | Demand Charge | Monthly Savings |
|---|---|---|---|---|---|---|---|---|
| Starter | 900 | 45 | 0.28 | 0.16 | 250 | 70 | 0 | Varies |
| With demand reduction | 1800 | 55 | 0.33 | 0.18 | 500 | 60 | 12 | Varies |
Numbers are illustrative. Your bill may include tiers, taxes, or credits.
Formula Used
- Peak kWh = Monthly kWh × (Peak share ÷ 100)
- Off-peak kWh = Monthly kWh − Peak kWh
- Shifted kWh = min(Shiftable kWh, Peak kWh) × (Shift % ÷ 100)
- Off-peak added = Shifted kWh × (1 + Efficiency loss ÷ 100)
- Energy cost = (Peak kWh × Peak rate) + (Off-peak kWh × Off-peak rate)
- Demand cost = Demand charge × Demand (kW)
- Monthly total = Energy cost + Demand cost + Fixed charges + Monthly program cost
- Monthly savings = Baseline total − New total
- Payback months = One-time equipment cost ÷ Monthly savings (when savings > 0)
How to Use This Calculator
- Enter your monthly kWh and peak share estimate.
- Add your peak and off-peak energy rates from the bill.
- Provide shiftable kWh and the percent you can shift.
- If applicable, include demand charges and expected kW reduction.
- Add any monthly fees and one-time equipment costs.
- Click “Calculate Savings” to view results and downloads.
Tip: Use conservative assumptions first, then test best-case scenarios.
Peak and Off‑Peak Price Signals
Time‑based pricing rewards customers who move flexible consumption away from constrained hours. When peak rates exceed off‑peak rates, each shifted kilowatt‑hour replaces a high‑cost unit with a lower‑cost unit, improving the blended energy price. The calculator quantifies this spread using your peak and off‑peak inputs. A larger spread increases savings, while a narrow spread makes fees more important.
Quantifying Shiftable Energy
Not all peak consumption can move. The shiftable kWh field represents controllable loads such as HVAC pre‑cooling, water heating, charging, or process scheduling. The percent shifted reflects operational reality. By capping shiftable energy at current peak kWh, the estimate stays conservative and avoids overstating savings. If your peak share is low, shifting may be limited even with high shiftable potential.
Energy Cost Before and After Shifting
Baseline energy cost equals peak kWh multiplied by the peak rate plus off‑peak kWh multiplied by the off‑peak rate. After shifting, peak kWh decreases by shifted kWh, while off‑peak kWh increases by shifted kWh adjusted for efficiency loss. This produces a revised energy cost that can be compared month to month. Efficiency loss models rebound effects and it can reduce net benefits.
Demand Charges and Operational Impact
Many commercial tariffs add a demand charge based on the highest measured kW in the billing period. If shifting reduces coincident peak demand, the demand reduction input converts directly into lower demand charges. However, poor scheduling can create a new peak. Use interval data to validate the expected kW reduction. Pair automation with guardrails, such as staggered starts, to prevent synchronized load spikes.
Savings, Payback, and Sensitivity
Monthly savings equals baseline total cost minus the new total cost, including fixed charges and any monthly automation fee. Annual savings scales the result to twelve months. If you enter a one‑time equipment cost, payback months equals equipment cost divided by monthly savings when savings are positive. Test scenarios by adjusting shift percent, rate spread, and demand reduction. Document assumptions alongside each scenario run.
FAQs
What is load shifting in simple terms?
Load shifting means moving flexible electricity use from expensive peak hours to cheaper off‑peak hours, without changing the monthly total usage much.
How do I estimate peak share if I lack interval data?
Use bill notes, thermostat schedules, and operating hours. Start with a conservative percentage, then adjust after reviewing a few months of seasonal patterns.
Why does efficiency loss reduce savings?
Some shifted actions may run longer or at less efficient conditions. The calculator adds extra off‑peak kWh to reflect that rebound, which lowers net savings.
When should I enter demand charges and kW values?
Enter them if your tariff bills a monthly charge per kW based on the highest measured demand. Use your bill’s demand value and a realistic kW reduction estimate.
Why can savings be negative?
Savings turn negative when the rate spread is small, efficiency loss is high, or monthly program costs exceed avoided peak and demand costs.
How should I use equipment payback results?
Treat payback as a screening metric. Compare it with expected equipment life, maintenance, and operational risk, and validate assumptions with real bill data.