Understand battery capacity, continuous load, efficiency, reserve, runtime and equipment priorities before selecting portable power for wildfire-related outages or smoke events.
Start with the equipment that must operate rather than the battery product you want to buy.
Decide whether the requirement is two hours, overnight, one day or a longer outage.
Inverters, electronics, battery management and reserve reduce nominal capacity available to equipment.
A smaller essential-load plan often provides more useful runtime than attempting to power everything.
Loss of grid power can affect communication, indoor-air filtration, lighting, refrigeration and other equipment that households or facilities may want to maintain during an outage.
A portable air cleaner cannot provide clean-air delivery without electricity. During a smoke event, backup power may therefore become part of an indoor-air plan.
The useful question is not simply how large the battery is, but how long it can support the required equipment.
Battery capacity is normally stated in watt-hours, while equipment demand is stated in watts.
Conversion losses, reserve, standby consumption, temperature and varying loads mean nominal capacity should not be treated as fully usable energy.
The first useful exercise is deciding what must remain powered. Each additional device consumes part of the available energy budget.
Phones, routers, radios and charging devices may require comparatively little energy but provide important connectivity.
Portable air cleaners may need to operate continuously during smoke exposure periods.
Efficient lighting can usually provide useful illumination with relatively modest continuous demand.
Refrigerators and similar equipment may cycle on and off and can also have startup demand above running power.
A useful planning model separates nominal battery capacity from the energy actually available to the connected load.
C is nominal battery capacity in watt-hours.
η represents assumed conversion efficiency.
R represents the fraction intentionally retained as reserve.
P is the continuous equipment load in watts.
The result is an estimated operating time in hours under the entered assumptions.
Change battery capacity, connected load, conversion efficiency and reserve. The dedicated calculator also estimates the capacity needed for 8 or 24 hours.
Open Portable Power Runtime Calculator →The following example illustrates why a nominal 2,048 Wh battery does not provide 2,048 Wh directly to the connected load.
Real systems consume or retain part of their nominal energy before it reaches the connected equipment.
AC inverters and internal electronics are not perfectly efficient, so some stored energy is lost during conversion.
A planning reserve can prevent the calculation from assuming that every nominal watt-hour will be deliberately consumed.
Inverter standby demand, displays, communications and other internal functions can consume additional energy.
This is the power that the battery system must be able to supply while equipment is operating normally. Continuous watts are also the principal input for a basic runtime estimate.
Motors, compressors and some appliances can briefly demand more power when starting. A battery may have enough energy for the runtime but still be unable to support the required startup surge.
Runtime is only one component of a resilient backup-power plan.
Battery capacity determines how much stored energy is available before recharging.
Inverter rating and surge capability determine whether the connected equipment can actually be supplied.
Grid, vehicle, solar or other charging options determine how quickly the stored-energy budget can be restored.
Priorities determine whether stored energy is spent on essential equipment or unnecessary demand.
Estimate the energy capacity and output you actually need, then compare products against that requirement rather than choosing only by advertised battery size.