How to Size Backup Power for Your Home

Choosing the right backup power size isn’t about buying the biggest system available—it’s about matching capacity to real needs.

This guide explains how to think about backup power sizing in practical terms, without complicated calculations.

Start With Essential Devices

Begin by identifying which devices truly need power during an outage. For most households, this includes refrigeration, lighting, communication equipment, and select medical devices.

Prioritizing essentials prevents overspending and reduces unnecessary complexity.

Output vs Capacity

Output determines whether a backup power system can start and run a device. Capacity determines how long that device can operate.

Both factors matter, but capacity is often underestimated—leading to shorter runtimes than expected.

For a deeper explanation of capacity, see Power Station Capacity Explained.

Short Outages vs Long Outages

For short outages, moderate-capacity systems may be sufficient. Longer outages require more capacity or the ability to recharge using solar panels or additional batteries.

Planning for realistic outage durations helps avoid disappointment during extended blackouts.

Avoid Common Sizing Mistakes

Common mistakes include focusing only on wattage, ignoring startup surges, and underestimating runtime needs.

A properly sized backup power system should provide peace of mind—not constant power management.

For appliance-specific needs, see Can a Solar Generator Run a Refrigerator?