Short answer
Choose a power station using two separate numbers: watt-hours for runtime and watts for simultaneous output. Add the daily energy needed by essential loads, multiply by outage duration, then allow for conversion losses and reserve. Separately, add loads that may run together and check motor or compressor startup requirements.
Home-backup sizing worksheet
Replace every example with a value from the appliance nameplate, manual, EnergyGuide label or a meter. Hours are expected operating hours per day.
| Essential load | Running watts | Hours/day | Daily Wh |
|---|---|---|---|
Planning estimate only. This sums listed running watts; it is not a startup-surge calculation. Confirm startup demand and compatibility in each manual.
How the calculation works
- Daily energy: running watts × expected hours for each load, then add the results.
- Outage energy: daily energy × planned outage days.
- Rated capacity: outage energy ÷ (1 − loss allowance) × (1 + reserve margin).
- Inverter output: add loads likely to overlap, then verify startup surge separately.
For a refrigerator or freezer, hours per day should reflect compressor cycling rather than assuming nameplate wattage runs continuously. Ready.gov says an unopened refrigerator keeps food cold for about four hours and a full freezer for about 48 hours, or 24 hours if half full.
Capacity classes: a practical screen
| Calculated capacity | What to compare | Main risk to check |
|---|---|---|
| Under 1 kWh | Small portable units for communications, lighting and short loads | Refrigerator runtime and surge |
| 1–2 kWh | Portable units for a compact essential-load plan | Overlapping loads |
| 2–4 kWh | Larger wheeled or expandable systems | Weight, recharge time and connection |
| Above 4 kWh | Expandable or installed backup systems | Transfer equipment, permits and installation |
These bands are shopping filters, not product recommendations. Compare usable energy, continuous output, surge limits, battery chemistry, warranty, charging inputs and expansion hardware.
Does your result fit the EcoFlow DELTA Pro?
The original DELTA Pro publishes 3.6 kWh base capacity and 3,600 W continuous AC output. Read the specification-led guide before comparing current bundles or expansion equipment.
Compare DELTA Pro for home backup →SolarStateData has an approved EcoFlow affiliate relationship. The guide currently uses a direct manufacturer link without commission tracking.
Sources and checking method
- Federal Trade Commission: EnergyGuide labeling FAQs.
- Ready.gov: Power Outages.
- EcoFlow US: DELTA Pro product page.
Sources checked 26 August 2026. SolarStateData has not physically tested the listed power station and does not assume these example loads match your equipment.
Frequently asked questions
How many watt-hours do I need?
Add watts × operating hours for every essential load, then adjust for losses, outage duration and reserve.
Are watt-hours and watts the same?
No. Watt-hours determine runtime. Watts determine how much equipment the inverter can supply at once.
Where should appliance watts come from?
Prefer the nameplate, manual, EnergyGuide label or a meter. Online averages are rough placeholders.