Path-Q Solar
How should I size backup when outages usually occur during the evening?
Answer
Size backup around the evening loads you actually need, the expected outage duration, and the battery's usable—not nameplate—capacity. Evening outages can be favorable if the battery is charged during the day, but the design must account for reserve, conversion losses, and any large loads that start after sunset.
Key points
- List critical evening loads separately from optional loads.
- Estimate energy in kilowatt-hours and peak or startup power in kilowatts.
- Include refrigerator cycling, lighting, communications, medical equipment, pumps, heating controls, and cooking equipment as applicable.
- Set an explicit minimum state-of-charge reserve for later or unexpected outages.
- Test the design for the longest outage duration that matters, not only the typical event.
What it depends on
- Outage duration and timing
- Critical-load energy and peak demand
- Battery usable capacity, power rating, and reserve policy
- Whether solar can recharge the battery the next day
Risks and trade-offs
- Including electric heating, water heating, or cooking can increase required capacity substantially.
- A smaller system costs less but may require load shedding or provide shorter backup.
- A design based on average evening use may fail when motors or heating equipment start.
Information you may need
- Interval electricity data or measured evening usage
- Critical-load list and appliance ratings
- Target outage duration and reserve requirement
- Battery usable capacity and inverter output
Your next step
What to do next
Ask installers to quote the same critical-load scenario with stated usable capacity, peak power, reserve, and expected hours of backup.
Path-Q
Find the right next step
Answer a few questions and we’ll narrow your options.
Loading…
SQ02283