Solar System Estimator

Calculate Inverter size & Battery storage (kWh) for backup power.

System Sizing Tool

Select appliances for backup power

Fans

75W

2

LED Lights

15W

6

Air Conditioner

1200W

0

Refrigerator

300W

1

Water Pump

800W

0

TV / Desktop

150W

1
4 Hours
1 Hr 12h 24h

More Calculators

Select a calculator below to get move further with your solar journey.

Cost Calculator

Estimate installation costs including equipment and labor.

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ROI & Payback

See how long it takes to break even and start profiting.

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How to Size a Solar System for Backup Power

Whether you are looking to survive power outages, reduce grid reliance, or go completely off-grid, sizing your Inverter and Battery bank correctly is the most critical step. A system that is too small will shut down when you need it most.

1. Hybrid vs. Off-Grid Systems

  • Hybrid Solar (Most Common): Connected to the grid but has batteries. It can sell power to the utility (Net Metering) and provide backup when the grid fails.
  • Off-Grid Solar: Completely disconnected from the utility company. Requires a much larger battery bank to account for cloudy days.
  • Grid-Tie (No Battery): The cheapest option, but it turns off during a power outage for safety reasons. Do not buy this if you need backup power.

2. Understanding Battery Types (kWh)

Lithium-Ion (LiFePO4)

The modern standard. Higher upfront cost ($300-$500 per kWh) but lasts 10+ years and can be discharged deeply (90%). Best for daily use.

Lead-Acid / AGM

Traditional technology. Cheaper upfront ($150-$200 per kWh) but only lasts 2-3 years and should not be discharged below 50%. Heavy maintenance.