For decades, most American homeowners paid a relatively simple electricity bill—a fixed rate per kilowatt-hour (kWh) that didn't change based on when they used power. You turned on the air conditioner at 4pm, ran the dishwasher at 9pm, and charged your electric vehicle at midnight, all at the same price per unit.

That model is rapidly changing. Across the United States, utility companies are shifting toward time-of-use (TOU) pricing structures that charge different rates depending on when electricity is consumed. This shift reflects the reality that generating and delivering electricity costs more during peak demand periods—and that incentivizing customers to shift usage away from those peaks can reduce the need for expensive new power plants and transmission infrastructure.

Understanding Time-of-Use Rates

Time-of-use pricing divides the day into multiple rate periods:

Off-Peak Hours: Typically late night through early morning, often from 9pm to 9am. Rates during these periods are significantly lower, sometimes 50% or more below peak rates.

Mid-Peak Hours: Transitional periods during the day, often weekday mornings and late evenings. Rates fall between off-peak and on-peak levels.

On-Peak Hours: Typically afternoon and early evening on weekdays, usually from 3pm to 9pm during summer months, though exact hours vary by utility and season. These periods command the highest rates—sometimes 300-400% of off-peak prices.

This pricing structure creates an opportunity for homeowners with solar plus storage systems: shift energy consumption to low-cost periods and draw on stored energy during expensive peak periods, potentially reducing overall electricity costs.

Why Utilities Are Adopting TOU Pricing

Several factors are driving the widespread adoption of time-of-use rates:

Grid Congestion: Traditional electricity grids were designed for peak demand, which occurs just a few hundred hours per year. Building and maintaining infrastructure for those occasional peaks is expensive. TOU pricing smooths demand curves, reducing the need for costly infrastructure expansion.

Renewable Integration: Solar panels generate electricity during midday when grid demand is high—but also when solar is most abundant. This can create oversupply during daylight hours and steep ramp-up requirements as solar production falls in late afternoon just as demand surges. TOU pricing helps align customer consumption with renewable availability.

Electric Vehicle Growth: As more homes adopt EVs, overall electricity demand increases, and most charging occurs overnight when EVs are parked. TOU pricing encourages off-peak charging, preventing new peak demands while utilizing off-peak generation capacity.

Demand Response Programs: TOU rates work alongside voluntary demand response programs where utilities request temporary load reductions during extreme grid stress events. Participating customers may receive bill credits or payments for reducing consumption on request.

How Solar Plus Storage Responds to TOU Rates

For homeowners with solar panels and battery storage, time-of-use optimization becomes a powerful cost-management strategy. Here's how it typically works:

Daytime: Solar Generation and Battery Charging

During daylight hours, solar panels generate electricity. With a hybrid inverter and battery system:

• Solar power first serves immediate household loads

• Excess generation charges the battery bank

• Any remaining power exports to the grid (if grid-tied, earning credits or compensation)

By evening, the battery is typically fully charged from solar production, storing that midday solar energy for use when rates are highest.

Evening Peak: Battery Discharge

When on-peak rates begin (typically 3pm-9pm), the system shifts strategy:

• The battery begins discharging to power the home

• Household consumption draws from stored energy rather than the grid

• Solar production during this period supplements battery discharge

The goal: minimize grid purchases during the most expensive hours while maximizing self-consumption of solar generation.

Off-Peak Night: Grid Supplementation (If Needed)

During off-peak hours, when rates are lowest:

• Any remaining household loads draw from the grid at low rates

• If battery capacity remains, the system may absorb additional cheap grid energy

• For systems with EV charging capability, nighttime is ideal for vehicle charging

This cycle repeats daily, optimizing consumption patterns to exploit the rate differential between periods.

The Role of iHEMS® in Time-of-Use Optimization

Manual optimization is possible but tedious—who wants to check utility rate schedules daily and manually adjust appliance usage? The iHEMS® platform automates this process through several intelligent mechanisms:

Dynamic Rate Integration

iHEMS maintains a database of rate structures from utilities across the United States. Currently, the platform supports dynamic pricing information from over 110 US utility operators, enabling automatic optimization for homeowners in participating service territories.

Automatic Scheduling

Based on your utility's rate schedule, iHEMS® automatically programs your system to:

• Charge batteries during lowest-rate periods (typically overnight)

• Pre-cool or pre-heat your home before peak rates begin (if smart thermostats are integrated)

• Defer non-essential loads to off-peak hours when possible

• Discharge batteries during peak-rate periods

AI-Powered Prediction

The iHEMS® platform includes AI capabilities that analyze 48-hour forecast data for weather conditions and solar production estimates. This predictive approach allows the system to:

• Anticipate whether solar generation will exceed household needs

• Adjust battery charging strategy based on expected cloud cover

• Optimize discharge timing based on anticipated consumption patterns

Load Flexibility Management

When paired with KAYIS SMART Breakers, iHEMS® gains circuit-level control over household loads. During extended peak periods or limited solar days, the system can automatically shed non-critical loads (such as pool pumps, electric dryers, or second refrigerator circuits) to extend battery runtime for essential services.

Important Consideration 

While time-of-use optimization has the potential to reduce electricity costs, results vary based on several factors:

Utility Rate Structure: The magnitude of savings depends on the difference between peak and off-peak rates. Utilities with minimal rate differentials offer less optimization opportunity.

Household Consumption Patterns: Homes with flexibility in when they run major appliances benefit most. Fixed schedules (such as someone home during peak hours for medical needs) may limit optimization potential.

System Size: Both solar generation capacity and battery storage capacity affect optimization potential. Larger systems can store more energy for strategic discharge.

Seasonal Variations: Rate periods often shift between seasons, and solar production varies dramatically. Summer cooling demands often coincide with peak rates, creating substantial optimization opportunities, while winter heating loads may shift optimal strategies.

A Realistic Perspective

It's worth emphasizing that time-of-use optimization is a strategy with potential benefits rather than a guaranteed outcome. Actual savings depend on your specific utility rates, consumption patterns, system configuration, and how consistently the optimization strategy aligns with your household needs.

The iHEMS® platform provides the intelligence and automation to execute this strategy effectively, but the foundation remains your hardware choices and how you balance optimization against lifestyle preferences.

VPP-Ready Capability

For homeowners interested in additional value opportunities, iHEMS®-connected systems have the potential to participate in Virtual Power Plant (VPP) programs where available. These programs aggregate distributed energy resources to provide grid services, potentially earning bill credits or payments for participants. Participation is voluntary and subject to local program availability.

Curious how time-of-use optimization might benefit your household? Visit [candlon.com](https://candlon.com) to learn more about solar plus storage solutions, explore iHEMS® capabilities, and connect with our team for a personalized assessment of your energy optimization potential.