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Time-of-Use Rate Plan Comparison

Compare a peak/shoulder/off-peak plan against a flat rate including both fixed charges, and find the peak share where they break even.

Inputs

Usage split

Total kWh for the month.

Percent of your kWh that falls in the peak window. From interval data when you have it; otherwise from your daily routine.

Percent in the shoulder or mid-peak window.

Flat plan

All-in rate on your current flat plan.

Customer charge on the flat plan, so both plans are compared including fixed costs.

Time-of-use plan

Peak-window energy rate.

Shoulder or mid-peak energy rate.

Off-peak energy rate. This is also the rate a battery would charge at for arbitrage.

Customer charge on the time-of-use plan.

Result

Annual savings with TOU
$-421
Flat plan bill
$229.25
Monthly savings with TOU
$-35.08
Savings as a share of the flat bill
-15.3 %
Time-of-use bill
$264.33
Peak share where the plans tie (0 or negative = TOU never wins)
2.6 %
Share falling in off-peak
50 %

What to check

  • Your actual load shape from interval data: the share of kWh in each window decides the answer, and intuition is usually wrong.
  • Both plans fixed charges, which this comparison now includes on each side.
  • Seasonal rate changes and whether peak windows shift between summer and winter.
  • Whether the plan requires a smart meter or has a minimum-bill provision.
  • A battery only wins here if it charges in the off-peak window and discharges in the peak window, and the round-trip losses are real.

Keep going

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Related guides

Comparison of two rate structures at a fixed monthly load split. It does not model seasonal rate changes, demand charges, or a battery shifting load between windows; a break-even figure below zero means the time-of-use plan does not win at any peak share with these rates.

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