Peak Hours, Demand Charges & Time-of-Use Rates Explained
Your electricity doesn’t cost the same at every hour of the day. When millions of people crank up their air conditioning on a hot afternoon, the cost to generate and deliver electricity spikes. Utilities and electricity providers pass these costs on through peak pricing, time-of-use rates, and demand charges — three related but distinct concepts that can significantly affect your bill.
What Are Peak Electricity Hours?
Peak hours are the periods of highest electricity demand on the grid. During these hours, more power plants are running (including expensive “peaker” plants that only fire up when demand is high), and the cost to generate each kWh increases substantially.
| Period | Summer Hours | Winter Hours | Demand Level |
|---|---|---|---|
| Off-peak | 9 PM – 6 AM | 9 PM – 6 AM | Low — cheapest rates |
| Shoulder | 6 AM – 1 PM | 10 AM – 5 PM | Medium — moderate rates |
| Peak | 1 PM – 7 PM | 6 AM – 10 AM, 5 PM – 9 PM | High — most expensive |
| Weekends & holidays | All day | All day | Off-peak rates typically apply |
Note: Exact peak hours vary by utility and electricity provider. In Texas (ERCOT), the system-wide peak typically occurs between 2 PM and 6 PM on summer weekdays.
Time-of-Use (TOU) Rates vs. Flat Rates
Most residential electricity customers are on a flat rate — they pay the same price per kWh regardless of when they use electricity. But an increasing number of providers now offer time-of-use (TOU) plans that charge different rates depending on the time of day.
| Feature | Flat Rate Plan | Time-of-Use Plan |
|---|---|---|
| Rate structure | Same rate 24/7 | Higher peak, lower off-peak |
| Best for | People home during the day | People who can shift usage to evenings/nights |
| Complexity | Simple to understand | Requires awareness of usage timing |
| Savings potential | Limited | 20–40% if you shift effectively |
| Risk | None — predictable | Higher bills if you can’t shift usage |
Example: TOU vs. Flat Rate Comparison
Consider a household using 1,000 kWh/month. On a flat-rate plan at 14¢/kWh, their bill is $140. On a TOU plan:
| Period | Rate | Usage (shifted) | Cost |
|---|---|---|---|
| Off-peak (9 PM – 6 AM) | 8¢/kWh | 500 kWh (50%) | $40.00 |
| Shoulder (6 AM – 1 PM) | 14¢/kWh | 250 kWh (25%) | $35.00 |
| Peak (1 PM – 7 PM) | 22¢/kWh | 250 kWh (25%) | $55.00 |
| Total | 1,000 kWh | $130.00 |
By shifting half their usage to off-peak hours (running laundry, dishwasher, and EV charger at night), this household saves $10/month — or $120/year. With more aggressive shifting, savings can exceed $200/year.
What Are Demand Charges?
Demand charges are different from time-of-use rates. While TOU rates are based on when you use electricity, demand charges are based on how much electricity you use at once — your peak instantaneous demand measured in kilowatts (kW).
Demand charges are most common on commercial and industrial electricity bills, though some residential plans (especially in states with high solar penetration) are beginning to include them.
How Demand Charges Work
Your utility or provider measures your highest 15-minute average power draw during the billing period. That single peak reading (in kW) is multiplied by the demand charge rate to determine the demand portion of your bill.
| Component | What It Measures | Unit | Typical Residential Impact |
|---|---|---|---|
| Energy charge | Total electricity consumed | ¢/kWh | 80–95% of bill |
| Demand charge | Peak instantaneous draw | $/kW | 0–15% of bill (if applicable) |
| Fixed charge | Monthly service/connection fee | $/month | 3–10% of bill |
“Think of it this way: energy charges are like paying for the total gallons of water you use. Demand charges are like paying for the size of the pipe you need — the bigger your peak flow, the more you pay.”
The “Free Nights” Plans in Texas
Several Texas electricity providers offer popular “free nights” or “free weekends” plans. These are a variation of time-of-use pricing where electricity is free during specific hours but costs more during the day:
| Plan Type | Free Hours | Daytime Rate (Typical) | Best For |
|---|---|---|---|
| Free nights | 9 PM – 6 AM | 18–25¢/kWh | Night owls, EV owners, families with evening routines |
| Free weekends | Fri 6 PM – Mon 6 AM | 16–22¢/kWh | People who do chores/laundry on weekends |
| Free nights + weekends | Both | 22–30¢/kWh | Heavy users who can shift most consumption |
These plans can save significant money for the right household, but they can also cost more if you use a lot of electricity during the daytime hours. The key is knowing your usage patterns before enrolling.
How to Save Money on Peak Electricity
- Pre-cool your home. Run your AC aggressively in the late morning (when rates are lower), then raise the thermostat 2–3 degrees during peak afternoon hours. Your pre-cooled home will coast through peak without much additional cooling.
- Run major appliances at night. Dishwasher, clothes dryer, washing machine, and pool pump can all be set to run during off-peak hours. Many modern appliances have delay-start timers built in.
- Charge your EV overnight. If you have an electric vehicle, set it to charge between 10 PM and 6 AM. This alone can save $30–$60/month on a TOU plan compared to daytime charging.
- Use a smart thermostat. Smart thermostats learn your schedule and can automatically pre-cool before peak hours and reduce usage during expensive periods.
- Consider battery storage. If you have solar panels, a home battery (like Tesla Powerwall) can store excess solar energy generated during the day and discharge it during peak evening hours, avoiding peak rates entirely.
Why Peak Pricing Is Becoming More Common
Three trends are making peak pricing increasingly important for consumers:
- Grid stress from electrification. As more homes adopt EVs, electric water heaters, and heat pumps, the evening demand peak is growing sharply. Utilities need price signals to spread this load.
- Solar duck curve. In states with heavy solar adoption, electricity is abundant (and cheap) during the day but scarce in the evening when solar drops off and people come home. This creates the famous “duck curve” that time-of-use rates aim to flatten.
- Smart meter deployment. Modern smart meters can track usage in 15-minute intervals, making granular time-of-use billing practical. Over 75% of U.S. electricity meters are now smart meters.
If you live in a deregulated state, compare plans in your area to see if a time-of-use plan could save you money based on your usage patterns.
Sources
U.S. Energy Information Administration (EIA), ERCOT grid operations data, PUCT rate filings, Department of Energy smart meter deployment reports, NREL time-of-use rate analysis. Last updated March 17, 2026.