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Home energy guide

How to size a home solar and battery system

Start with energy and power needs, then test the design against site conditions.

By Solar System Installations EditorialEdited: Solar System Installations EditorialUpdated August 1, 2026

Gather useful energy data

Collect at least 12 months of utility usage when possible, not just the bill amount. Note seasonal peaks, rate plans, outages, and planned loads such as an EV, heat pump, induction range, or workshop.

Separate kW from kWh

kW measures power at a moment; kWh measures energy over time. A battery can have enough stored energy for several hours but still lack the instantaneous power for every large appliance. Build an essential-load and whole-home load list.

Estimate solar within real constraints

Roof planes, shade, orientation, weather, setbacks, structure, and utility limits shape the array. Model conservative losses and avoid treating a production estimate as a guarantee.

Test backup scenarios

Ask how the design performs during a winter outage, after a cloudy day, and with different state-of-charge limits. Confirm which circuits are backed up and how load management works. Compare system types and start an assessment.

Apply this to your home

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