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Battery Sizing & Backup Storage

Solar Battery Storage Sizing Calculator

Estimate storage requirements, sizing parameters, and battery backup costs to shield your home from grid outages.

Realistic Solar ROI Calculator

Calculate your solar panel payback period and savings

Estimate the cost of installing solar panels, annual savings on utility bills, federal tax credits, and the return on investment over 25 years.

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Adjust currency, tax settings, and utility baselines.

SOLAR

1. Sizing your system

We suggest a system size based on your monthly bill, or you can set it manually.

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Capacity 7.5 kW

2. Installation costs & incentives

Configure installation prices, battery options, and credits.

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3. Utility settings & net metering

Customize electric rates, utility inflation, and net metering buybacks.

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Is solar battery storage worth it?

Adding battery storage (such as a Tesla Powerwall, Enphase 5P, or FranklinWH battery) typically adds **$8,000 to $15,000** to the gross cost of a solar installation. Whether this investment makes sense depends on your goals:

1. Resiliency Against Grid Blackouts

Without a battery backup, a solar panel system will automatically shut down during a grid power outage. This safety mechanism protects utility workers. If you need power during an outage, a battery backup isolates your home and keeps critical appliances running.

2. Shifting Time-of-Use (TOU) Rates

If your local electric utility charges high peak rates (typically in the late afternoon/evening), you can charge your battery with solar panels during the day and consume the battery power during peak hours, avoiding high grid electric bills.

3. Maximizing Low Net Metering Returns

In states with low net metering buybacks (avoided cost rates), exporting solar power to the grid yields very little credit. Storing that excess power locally and consuming it at night yields a much higher financial return.