Savings and payback

Time of use rate savings calculator

Estimate your solar savings under a time-of-use plan by accounting for how much of your production actually lands during peak pricing hours.

For planning purposes only, not financial or tax advice; confirm figures with a licensed installer or tax professional before making a purchase decision.

Your numbers

1 Usage and production
Use the production figure from the solar savings calculator if needed.
2 Peak and off-peak rates
3 Timing overlap
Portion of your total usage that happens during your utility's peak window.
Solar peaks midday. If your utility's peak window is evening, this is often 15 to 25%.

How it works

Three steps to your TOU savings

Step 1

Enter your usage and solar offset

Use annual figures for both. The solar savings calculator can help estimate offset if needed.

Step 2

Add your peak and off-peak rates

Check your utility's TOU rate schedule for both figures, which can differ significantly, sometimes by more than double. If your bill uses a different structure entirely, the flat vs tiered rate comparison may fit better.

Step 3

Estimate your timing overlap

This is the key input most flat-rate tools skip. If your peak window is evening rather than midday, your savings will run lower than a simple blended-rate estimate.

Understanding time-of-use savings

Why timing overlap changes everything

In one example, a system saved $1,590 a year under a real TOU calculation, compared to $1,926 that a simple blended-rate estimate would suggest. The gap exists because only 20% of the example's solar production landed during peak hours, while 35% of usage did, meaning most solar output offset cheaper off-peak electricity instead of the pricier peak-hour kind. The US Energy Information Administration's solar explainer covers how solar generation works and where it fits in the wider grid.

The duck curve problem

Solar production is naturally concentrated between late morning and mid afternoon, following the sun. Many utilities set peak pricing in the late afternoon and evening instead, when solar output is dropping just as household demand rises from air conditioning, cooking, and evening activity. This mismatch, often called the duck curve, is a real limitation of solar under TOU billing without storage, and it's part of why the peak shaving savings estimator looks specifically at reducing demand during those hours. The production figure behind this estimate comes from the peak sun hours calculator, which models output for your location and roof.

How battery storage changes the picture

A battery can store midday solar production and discharge it during expensive peak hours instead of letting it export to the grid at a lower credit rate. This can substantially improve TOU savings, since it shifts more of your production overlap toward peak pricing. See the battery vs without battery comparison for that scenario in detail. A battery shifts when you use your solar power, and the battery charge time from solar calculator sizes one for your evening usage.

Comparing TOU to other rate structures

Not every utility uses time-of-use pricing. Some bill a flat rate, and others use tiered pricing based on total usage instead of time of day. See the flat vs tiered rate comparison if either matches your bill better. Utility rates drive the whole savings calculation, and the US Energy Information Administration's electricity data track them state by state.

Questions

Frequently asked

Not necessarily. If your utility's peak pricing window falls in the evening, after solar production has dropped off, much of your production ends up offsetting cheaper off-peak usage instead. In one example, savings came to $1,590 a year, noticeably less than the $1,926 a simple blended-rate estimate would suggest.

Most solar production happens between late morning and mid afternoon. Many time-of-use plans set peak pricing in the late afternoon and evening instead, when solar output is falling and household usage is rising, a mismatch sometimes called the duck curve.

Check your utility's peak hours against typical solar production hours for your location, usually 10am to 4pm. If your peak window overlaps heavily with those hours, use a higher overlap percentage. If peak hours are mostly evening, use a lower one, often 15 to 25%.

Yes, significantly. A battery lets you store midday solar production and use it during expensive peak hours instead of exporting it. The savings with battery vs without battery tool compares that scenario directly.

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