# Time-of-Use Rates and Solar: Why When You Use Power Matters as Much as How Much

> On a time-of-use rate, a solar kWh can be worth 3¢ or 30¢ depending on the hour. We use Idaho Power's 2026 tariff and Hawaiian Electric's export credits to show how the clock changes solar and battery value.

- URL: https://solarexaminer.com/posts/time-of-use-rates-and-solar/
- Site: Solar Examiner (https://solarexaminer.com/)
- Category: Solar Costs & Incentives
- Published: 2026-10-08
- Last verified: 2026-10-08
- Author: Tehseen Arbab

## Key takeaways

- On a time-of-use (TOU) rate, the price of electricity depends on the hour. Solar produces most around midday, when TOU prices are usually lowest.
- On Idaho Power's optional TOU plan, a summer evening on-peak kWh costs 29.9185¢, four times the 7.4797¢ off-peak price.
- Some export credits also vary by hour. Hawaiian Electric pays 13.5¢ on Oahu for daytime exports and 32.9¢ from 5 p.m. to 9 p.m.
- That gap is what a battery earns: storing a midday kWh worth 3.4¢ to export and using it at 7 p.m. to avoid 29.9¢ is worth about 23.5¢ in our Idaho example, assuming 90% round-trip efficiency.



Most home electricity is sold at the same price per kilowatt-hour (kWh) all day. A time-of-use (TOU) rate changes that: power costs more in the hours when the grid is busiest and less the rest of the time. For a solar home, the clock now decides what each kWh is worth.

## The Short Answer

| | Flat rate | Time-of-use rate |
|---|---|---|
| Price per kWh | Same all day | Higher in peak hours, lower off-peak |
| Midday solar offsets | The standard price | Usually the cheapest price |
| Evening use (no sun) | The standard price | Usually the most expensive price |
| Value of shifting use to midday | None | Can be large |
| Value of a battery | Backup, and higher self-use under net billing | Also moves cheap midday power into expensive hours |

## A Real Tariff: Idaho Power, 2026

Idaho Power's Schedule 6, for residential customers with on-site generation, offers an optional TOU plan alongside its standard plan. Both carry the same $15.00 monthly service charge.

**TOU energy prices, effective January 1, 2026:**

| Season | Period | Hours | Price per kWh |
|---|---|---|---|
| Summer (June 1 to Sept. 30) | On-peak | 7 p.m. to 11 p.m., Mon. to Sat. | 29.9185¢ |
| | Mid-peak | 3 p.m. to 7 p.m., Mon. to Sat. | 14.9594¢ |
| | Off-peak | All other hours, all day Sun. and holidays | 7.4797¢ |
| Non-summer | On-peak | 6 a.m. to 9 a.m. and 5 p.m. to 8 p.m., Mon. to Sat. | 13.8347¢ |
| | Off-peak | All other hours, all day Sun. and holidays | 9.2231¢ |

**Export credits on the same schedule (paid on every exported kWh):**

| Season | Period | Hours | Credit per kWh |
|---|---|---|---|
| Summer | On-peak | 3 p.m. to 11 p.m., Mon. to Sat. | 15.6836¢ |
| Summer | Off-peak | All other hours | 3.3920¢ |
| Non-summer | All hours | | 2.9019¢ |

The export on-peak window (3 p.m. to 11 p.m.) is wider than the TOU on-peak window (7 p.m. to 11 p.m.).

## What One kWh Is Worth at Different Hours

Here is what a single solar kWh is worth on a summer weekday for a home on Idaho Power's TOU plan:

| When the kWh is produced | Used in the home, it avoids | Exported, it earns | Better choice |
|---|---|---|---|
| Noon (off-peak) | 7.4797¢ | 3.3920¢ | Use it |
| 4 p.m. (mid-peak) | 14.9594¢ | 15.6836¢ | Export, by 0.72¢ |
| 7:30 p.m. (on-peak) | 29.9185¢ | 15.6836¢ | Use it |

Three things stand out:

1. **Midday is the cheapest time on the TOU rate,** and that is when panels produce the most. Each midday kWh offsets only 7.5¢.
2. **Late afternoon is the sweet spot** for west-facing panels. Production is lower, but both the price and the export credit are higher.
3. **After 7 p.m. the sun is low or gone,** and the price is at its highest. Solar alone does little here. A battery does.

Outside summer the gaps narrow. The difference between non-summer on-peak and off-peak is 4.6¢, and every exported kWh earns 2.9019¢.

## What a Battery Earns From the Gap

A battery can store a midday kWh and release it in the evening. Its value is the difference between the two hours, less what is lost in charging and discharging.

**Value per kWh shifted = (evening price × round-trip efficiency) − (value of the midday kWh you gave up)**

Using Idaho Power's summer TOU prices and assuming a 90% round-trip efficiency:

- Store a noon kWh that would otherwise be exported for 3.3920¢.
- Release it between 7 p.m. and 11 p.m., avoiding 29.9185¢ on 0.9 kWh.
- Value: (29.9185¢ × 0.9) − 3.3920¢ = **23.5¢ per kWh shifted**.

Shifting 10 kWh a day is worth about $2.35 on a summer weekday (10 × 23.5¢).

This is an illustration, not a payback estimate. The 90% efficiency is an assumption. The gap applies only on summer weekdays (Monday to Saturday, June through September) and is much smaller the rest of the year. Battery cost, degradation and your actual evening use decide whether it pays.

## Export Credits That Change by the Hour: Hawaii

Some utilities set the export credit itself by time of day. Hawaiian Electric's Smart Renewable Energy Export program pays these rates for 2024 to 2026:

| Island | Overnight (9 p.m. to 9 a.m.) | Daytime (9 a.m. to 5 p.m.) | Evening peak (5 p.m. to 9 p.m.) |
|---|---|---|---|
| Oahu | 18.9¢ | 13.5¢ | 32.9¢ |
| Maui | 13.1¢ | 6.6¢ | 18.2¢ |
| Hawaii Island | 14.8¢ | 10.6¢ | 23.1¢ |
| Molokai | 17.4¢ | 17.9¢ | 27.2¢ |
| Lanai | 25.9¢ | 26.7¢ | 40.8¢ |

On Oahu, an exported kWh is worth 2.4 times as much in the evening peak as at midday (32.9 ÷ 13.5). Hawaiian Electric locks these rates for the first seven years of a new interconnection agreement, and leftover credits expire at the annual true-up. It also offers a separate battery incentive, BYOD Plus, for batteries that provide a grid service.

## Is TOU Right for Your Solar Home?

A TOU plan tends to help when:

- You can run dishwashers, laundry, pool pumps or EV charging in the middle of the day.
- You have, or plan to add, a battery.
- Your panels face west and produce into the late afternoon.

It tends to hurt when:

- Most of your use falls in the evening peak and you cannot move it.
- You have electric heat or cooling that runs hard in peak hours without a battery.

**How to compare:** take 12 months of hourly or interval data from your utility's online account, if it offers it, and price your usage under both plans. Some utilities run this comparison for you.

## Questions for Your Installer

1. Does the savings estimate assume a flat rate or a TOU rate? Which one is my utility's default for new solar customers?
2. What share of my production falls in each TOU period?
3. If you recommend a battery, what value per kWh did you assume, and on how many days a year?
4. Would west-facing panels change the result?

Our [export credit comparison](/posts/solar-export-credit-rates-by-utility-2026/) and [solar payback guide](/posts/solar-payback-period-without-federal-tax-credit/) cover the rest of the calculation.

## Limitations

- The examples use two utilities. TOU hours, prices and eligibility differ widely, and many utilities have no TOU plan for solar customers.
- Idaho Power's TOU plan is optional and its standard plan uses tiered prices instead, from 12.1195¢ to 14.6185¢ in summer.
- The battery example assumes 90% round-trip efficiency and ignores battery cost and wear.
- Figures were checked on October 8, 2026. Confirm current tariffs with your utility.

## Sources

- [Idaho Power, Schedule 6: Residential Service On-Site Generation (rates effective January 1, 2026)](https://docs.idahopower.com/pdfs/aboutus/ratesregulatory/tariffs/313.pdf)
- [Hawaiian Electric, Smart Renewable Energy Export](https://www.hawaiianelectric.com/products-and-services/smart-renewable-energy-programs/smart-renewable-energy-export)

## Frequently asked questions

### What is a time-of-use electricity rate?

A rate where the price per kWh changes by time of day, and often by season and day of the week. Electricity costs more in peak hours, usually late afternoon and evening, and less at other times.

### Is a time-of-use rate good for solar owners?

It depends on when you use power. Solar produces most around midday, when TOU prices are usually low, so it offsets cheaper kWh. Homes that can shift use into sunny hours, or that have a battery to cover the evening peak, tend to benefit more.

### What are Idaho Power's time-of-use hours?

On its 2026 optional TOU rate for on-site generation customers, summer on-peak is 7 p.m. to 11 p.m. and mid-peak is 3 p.m. to 7 p.m., Monday through Saturday except holidays, June 1 to September 30. Outside summer, on-peak is 6 a.m. to 9 a.m. and 5 p.m. to 8 p.m., Monday through Saturday.

### Do batteries pay off on a time-of-use rate?

A battery earns the difference between what a stored kWh would have earned or cost at the time it was charged and what it avoids at the time it is used. Whether that covers the battery's price depends on its cost, its size, how many days the price gap applies and how long it lasts. This guide does not calculate battery payback.


Image credit: Photo by James Coleman on [Unsplash](https://unsplash.com/photos/house-with-illuminated-windows-at-dusk-xoNUuUdWGF4?utm_source=solarexaminer&utm_medium=referral)