Essential-loads or whole-home backup?
| Approach | Common goal | Main tradeoff |
|---|---|---|
| Essential loads | Refrigeration, lights, internet, outlets, select pumps | Lower storage and inverter requirement |
| Partial home | More circuits with active load management | Requires priorities and discipline |
| Whole home | Broad coverage with fewer manual choices | Higher cost; large HVAC and resistance loads dominate sizing |
Build the estimate in four steps
- List critical circuits. Include devices that cycle or surge, such as refrigerators, well pumps and sump pumps.
- Estimate daily energy. Appliance wattage multiplied by realistic run time gives watt-hours.
- Check simultaneous power. The inverter must support the loads likely to operate together, including starting surges.
- Add reserve and losses. Usable capacity, temperature, conversion losses, aging and minimum state of charge all matter.
Battery with or without solar
A grid-charged battery can provide outage support without rooftop solar, subject to equipment and local rules. Solar can recharge compatible storage during an extended outage, but only if the system is designed for islanded operation. Ordinary grid-tied solar commonly shuts down during an outage for utility-worker safety.
Planning estimate only
Our calculator is useful for comparing scenarios, but final circuit selection, conductor sizing, overcurrent protection, transfer equipment and permitting require qualified professionals.
Questions for every battery proposal
- What usable energy and continuous/peak power are guaranteed?
- Which circuits are backed up, and what happens if loads exceed inverter capacity?
- Can the system expand later?
- Can solar recharge it during a grid outage?
- What are the warranty throughput, capacity-retention and service terms?
- Who supports the system if the installer closes?