How does home solar affect my electricity bill during peak and off-peak hours?

Understanding Peak and Off-Peak Hours

Electricity rates often vary by time of day. Utility companies charge more during peak hours when demand is high (typically late afternoon and early evening) and less during off-peak hours (usually overnight and midday). How your solar system affects your bill depends on your local utility’s rate structure and whether you have a time-of-use (TOU) plan.

How Solar Generation Aligns With Your Usage

Solar panels produce the most electricity during midday, which typically falls within off-peak or mid-peak periods. This means:

• During off-peak hours, your panels may generate more power than you use, sending excess energy back to the grid in exchange for credits (net metering).
• During peak hours (evening), your panels produce little to no power, so you draw from the grid or your stored battery.

Without a battery, you rely on grid power during peak hours, which can be expensive. With net metering, the credits earned during off-peak generation can offset some of those peak costs, but the exact savings depend on your utility’s buyback rate.

Net Metering and Time-of-Use Plans

Net metering allows you to export surplus solar energy for credits. On a TOU plan, the value of those credits varies:

• High-value credits are earned when you export during peak hours (rare for solar, since peak is often after sunset).
• Lower-value credits are earned during off-peak exports (most common with solar).

Some utilities use “net billing” where you sell power at a wholesale rate and buy at retail. Check your utility’s policy to understand the ratio.

Battery Storage Shifts Your Savings

A home battery can store solar energy during the day and discharge it during peak evening hours. This reduces your reliance on expensive grid power during peak times. Benefits include:

• Using stored solar power at night instead of buying from the grid.
• Avoiding peak-time electricity rates.
• Providing backup power during outages (depending on battery design).

Batteries are a significant investment, but they can improve payback in areas with strong TOU rate differentials.

Real-World Example (Simplified)

Assume your home uses 10 kWh during peak hours (6-9 PM) and your solar generates 20 kWh during off-peak (10 AM-3 PM). Without a battery:

• You export 20 kWh during off-peak, earning credits at $0.10/kWh = $2.00 credit.
• You buy 10 kWh during peak at $0.30/kWh = $3.00 cost.
• Net bill = $1.00 owed.

With a battery that stores 10 kWh for evening use:

• You use 10 kWh from battery during peak, avoiding $3.00 purchase.
• Net bill = $0 (plus any fixed fees).

Your actual numbers will vary based on rates, panel output, and local net metering rules.

Factors That Influence Your Bill

• Utility rate structure: Fixed vs. TOU plans.
• Net metering policy: Full retail credit vs. reduced buyback.
• System size vs. consumption: Oversized systems may not always save more.
• Seasonal changes: Shorter winter days reduce generation.
• Local regulations: Some areas limit net metering or require specific meters.

Steps to Maximize Savings

1. Review your utility’s TOU schedule (peak, off-peak, super-peak periods).
2. Check your net metering rate and cap (if any).
3. Consider a battery if peak rates are high and you use significant energy in the evening.
4. Shift high-usage activities (laundry, dishwashing) to off-peak when possible.
5. Monitor your system with a production app to track generation and export credits.

Important Caveats

Solar savings are not universal. Your location, utility, and system design all play a role. Some utilities have low or no net metering, which can reduce the financial benefit of solar. Always get a personalized estimate from a reputable installer who reviews your actual usage and local rate structures.

This content is for general educational purposes. Consult a qualified solar installer or your utility for specific information about your home and local regulations.