The same kilowatt-hour costs different dollars depending on the clock. This guide walks through the peak vs off-peak energy cost calculator—peak rate, off-peak rate, shiftable kWh, and how the spread converts into monthly and annual bill savings.
Benefits
- Side-by-side peak and off-peak $/kWh with the savings spread per shifted kWh.
- Cost comparison: what the same kWh costs on peak vs. off-peak before shifting.
- Monthly and annual savings when flexible load moves to the cheaper block.
How it works
- Look up peak and off-peak energy rates ($/kWh) on your utility TOU schedule.
- Note how many kWh per month you can run during off-peak instead of peak.
- Apply savings = shiftable kWh × (peak rate − off-peak rate) for bill impact.
FAQ
How do I compare peak vs off-peak energy cost?
Subtract off-peak $/kWh from peak $/kWh to get the spread. Example: $0.45 peak vs. $0.13 off-peak → $0.32/kWh spread. One kWh on peak costs $0.45; the same kWh off-peak costs $0.13—a $0.32 difference per kWh shifted. Multiply the spread by monthly shiftable kWh for savings.
Why is peak electricity more expensive than off-peak?
Utilities price peak hours when grid demand is highest—generation and transmission are stressed. Off-peak nights and mid-day solar-heavy windows often have surplus supply, so rates drop to encourage load shifting. TOU tariffs pass that price signal to your bill.
Can I use this for shoulder or mid-peak rates?
This tool models a two-block peak vs. off-peak spread—the core TOU comparison. If your tariff has shoulder periods, use the highest rate you are shifting away from as peak, or try the electricity rate plan calculator for three-tier splits.
Technical specifications
- Peak energy cost = peak_kWh × peak_rate.
- Off-peak energy cost = off_peak_kWh × off_peak_rate.
- Savings per shifted kWh = peak_rate − off_peak_rate.
- Related: calculate-savings-from-peak-load-shifting, electricity-rate-plan.
Two prices for the same electron
A kilowatt-hour is a kilowatt-hour—but your tariff tags it with a time stamp. Running a 3 kWh dryer cycle at 6 p.m. on a $0.44 peak block costs about $1.32; the same cycle at 10 p.m. on $0.12 off-peak costs $0.36. The peak vs off-peak gap is why scheduling matters more than buying a slightly more efficient dryer.
Spread × shiftable kWh = your savings budget
Wide spreads reward aggressive shifting; narrow spreads reward patience or staying on flat rate. Enter your actual rider rates—not a blog average—and honest shiftable kWh. The calculator multiplies the two; if the product looks small, the fix is either more movable load or a tariff change, not fancier math.
Read the bill in blocks, not blends
Blended $/kWh on a summary line hides peak pain. Interval data or utility apps show kWh by period. Once you see 180 kWh on peak last month, multiply by your peak rate and compare to what those kWh would cost off-peak—that before/after picture motivates timers better than a generic save-money tip.