Quick answer: A typical home with essential loads averaging 1,000W needs roughly 12–15 kWh installed capacity to run 12–24 hours during an outage, accounting for depth of discharge.
Home Battery Backup Calculator
Size your backup system for grid outages. Enter your critical loads and outage scenario to get kWh requirements and product recommendations — no solar required.
How we calculate home backup sizing
Required battery capacity is calculated by summing watt-hours for all selected critical loads over the target outage duration, then dividing by usable depth of discharge.
The result is matched to product tiers — portable stations, home batteries, or generator hybrids — based on the kWh and peak power requirements.
Frequently Asked Questions
- How much battery backup do I need for my home?
- Most homes need 10–20 kWh for 24-hour backup of essential loads. Add AC and you can double that requirement quickly.
- What's the difference between a home battery and a portable power station?
- Home batteries (Powerwall, Franklin, Enphase) are permanently installed, higher capacity, and integrate with solar. Portable stations are smaller, mobile, and require no installation.
- Can I run my whole house on battery backup?
- Whole-home battery backup is possible but expensive — typically $20,000–$40,000+. Most homeowners back up essential circuits only.
Reviewed April 2026
Methodology and source note
PowerSizing calculators use shared formulas, documented assumptions, and current planning inputs that are summarized on the methodology page. Use these tools for first-pass planning, comparison, and sanity checks, then confirm local code, pricing, utility tariff, and installer specifics before you buy equipment.