Phones
Planning default: 15Wh per full charge. Edit if you know the battery size.
Wh/charge
charges/day
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Household backup-power planner
How much backup power do you actually need?
Build a realistic load from the people and devices you want to support. The planner separates energy, continuous output and startup surge so one number does not pretend to answer three different questions.
Step 1 · Scenario
Describe the outage you are planning for.
The people count helps set sensible phone assumptions and gives the result household context. It does not automatically invent extra appliances.
people
Metric: household size.
Used for: context and the “one phone per person” shortcut. It does not directly create watts.hours
Metric: planning horizon.
Used for: continuous devices and the number of daily charging cycles. It is not an outage forecast.%
Metric: estimated share of stored battery energy that reaches the loads.
Used for: converting device energy into nominal battery capacity. AC inverter use is rarely 100% efficient.%
Metric: capacity deliberately left unused.
Used for: avoiding a plan that depends on draining the battery to its theoretical limit.Step 2 · Device load
What needs to keep working?
Each row uses either watts × hours for equipment that runs, or Wh per charge × charges for rechargeable devices. Every assumption is editable.
DeviceQtyPower / chargeUseEnergyPriority
Tablets
Planning default: 30Wh per full charge.
Wh/charge
charges/day
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Laptops
Planning default: 60Wh per full charge. Larger laptops can be substantially higher.
Wh/charge
charges/day
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Router + fibre ONT / modem
Planning default: 15W combined. Measure your actual boxes for a better result.
W each
hours total
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LED room lights / lantern charging
Planning default: 5W per light while powered/charging.
W each
hours total
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Fridge / freezer
Planning default: 60W average per unit. Compressor cycling varies; startup surge is checked separately.
avg W each
hours total
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Television
Planning default: 80W. Check the label or a plug-in energy meter.
W each
hours total
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Low-power medical / CPAP-type device
Placeholder planning row only. Replace 40W with the actual equipment requirement and follow manufacturer/clinical guidance.
W each
hours total
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Enter actual watts if possible. This row is deliberately not pre-filled with a guessed load.
W each
hours total
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Important:
These are transparent planning defaults, not claims about your actual appliances. Edit them. For fridges, pumps, compressors and some tools, startup surge can be much higher than average running watts.
Your result
Household backup plan.
Planning qualityUses editable defaults
Nominal battery capacity to investigate
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Device energy required
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before efficiency + reserve
Estimated simultaneous load
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if all runtime devices run together
Largest indicated surge
—
known planner value, not a guarantee
Where the energy goes
Energy by device.
Quick runtime
Battery capacity ÷ real load.
This mode is for one known average load. Use Household Planner when multiple devices have different usage patterns.
Estimated usable runtime
—hours
Enter a load to estimate runtime.
How the household calculation works
Transparent maths, not a magic recommendation.
Runtime device energy: quantity × average watts × total hours used.
Rechargeable-device energy: quantity × Wh per charge × charges per day × outage days.
Battery capacity to investigate: total device Wh ÷ efficiency ÷ (1 − reserve).
Continuous output: the combined watts of runtime devices that could operate together.