How many peak sun hours do I get per day?

Peak sun hours refer to the equivalent hours per day when solar irradiance averages 1,000 W/m². Most locations in North America and Southern Asia receive between 4.0 and 5.5 peak sun hours daily, distinct from total daylight hours.

What is the typical payback period for residential solar?

With the 30% federal tax credit and net metering, most residential grid-tied solar systems break even within 6 to 9 years, generating 15 to 20 years of completely free electricity over their 25-year warranty period.

How much battery storage (kWh) do I need for a home?

An average residential home consumes 10 to 15 kWh overnight. A 10kWh to 15kWh lithium LiFePO4 battery (like Tesla Powerwall or Enphase 5P) provides sufficient capacity to cover overnight loads and basic emergency backup.

What is Solar Net Metering (NEM)?

Net Energy Metering allows solar owners to send excess daytime solar electricity to the utility grid in exchange for utility bill credits, drawing power back from the grid at night.

How much do solar panels degrade over time?

Modern Tier-1 monocrystalline solar panels degrade at approximately 0.5% per year, retaining over 85% to 88% of their original nameplate power output after 25 years of service.

DIY & Trades

Solar Panel ROI, Payback Period & Lithium Battery Sizing Calculator

Name: Solar Panel Payback Period & Battery Sizing Calculator
Author: AnshuTechy

Calculate solar panel system size (kW), required lithium battery storage (kWh), 25-year financial ROI, and breakeven payback years. Accounts for federal tax incentives, net metering, and utility escalation rates.Documentation & FAQs ↓

Solar Panel Payback Period & Battery Sizing Calculator — Interactive Console

Runs locally in your browser • Instant output

Average Monthly Electric Bill ($)

~1028 kWh consumed per month

Electricity Rate ($/kWh)US Average: $0.16–$0.24/kWh

Peak Sun Hours / Day4.8 hrs

Sunshine irradiance equivalent

Solar Energy Offset Target100%

Battery Backup Autonomy1 Day(s)

Federal Solar Tax Credit30%

Recommended Solar Size8.9 kW23 × 400W Panels

Battery Capacity40.3 kWhLiFePO4 Backup Storage

Payback Breakeven17.4 YearsNet Cost: $38647

25-Year Net Profit$16853Cumulative Clean Savings

Step-by-Step Instructions

4 Steps to Completion

1Phase 1

Enter your average monthly electric bill amount and current utility tariff rate ($/kWh).

2Phase 2

Select average daily peak sunlight hours (typically 4.0 to 5.5 hours across the US and India).

3Phase 3

Specify desired solar offset percentage (e.g. 100%) and required days of battery backup autonomy.

4Phase 4

Inspect the recommended kW solar array, battery storage size, total estimated system cost, and payback years.

Practical Use Cases & Real-World Scenarios

Evaluating Solar Installer Quotes

Verify contractor equipment sizing proposals before signing costly $20,000+ solar leasing contracts.

Off-Grid & RV System Planning

Size solar panels and lithium battery banks to power off-grid cabins, camper vans, or remote workshops.

Blackout & Emergency Backup Planning

Determine how many kilowatt-hours of battery backup are required to keep refrigerators and lights running during storms.

Solar Panel ROI, Payback Period & Lithium Battery Sizing Calculator

Step-by-Step Instructions

Practical Use Cases & Real-World Scenarios

Peak Sun Hours Sizing

Battery Autonomy Calculator

Incentives & Tax Credits

25-Year Cumulative ROI Curve

Frequently Asked Questions

15 Best Electrical Tools in 2026

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