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Resilience: solar + storage
A grid‑tied photovoltaic system typically shuts down during an outage (anti‑islanding). Add a battery + transfer equipment to keep essential loads running safely.
Energy capacity (kilowatt-hour) and power capability (kilowatt). You need both.
Outage playbook
Step 1: List critical loads and their power draw (watts). Don’t guess—read the nameplate or measure with a plug meter.
Open the outage calculator Build a device list, estimate runtime, and email yourself the report.
Step 2: Decide runtime (hours) you want to cover without sun.
Step 3: Separate surge loads (fridge compressor, well pump) from steady loads (lights, router).
| Load | Typical W | Notes |
|---|---|---|
| wireless internet + modem | 10–30 | Low energy, high value. |
| Refrigerator | 100–250 | Startup surge can be 2–6×. |
| LED lights | 5–15/bulb | Switch to LEDs for resilience + savings. |
| Medical device | Varies | Plan with margin and redundancy. |
Backfeeding a home without proper transfer equipment is dangerous to line workers and can damage electronics. Always use a code-compliant inverter/transfer system.
Design patterns
- Critical loads panel (keep it simple)
- Whole-home backup (bigger battery + inverter)
- Generator integration (optional, for long outages)
Battery sizing: kilowatt-hour vs kilowatt
kilowatt-hour determines how long you can run loads. kilowatt determines what you can start and run simultaneously.
Example: A 10 kilowatt-hour battery can run a 500 W load for ~20 hours (ignoring losses). But if your inverter can only deliver 3 kilowatt, you might not be able to start a large motor load.
Rule of thumb: plan 10–20% headroom and account for inverter efficiency and battery reserve settings.
- Identify surge loads and inverter surge rating.
- Choose critical loads: fewer loads = smaller, cheaper system.
- Ask about black start behavior and cold-weather performance.
- Verify interconnection rules if exporting from storage.