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Practical guide

Build a critical-load audit before choosing a battery

List only the loads that protect safety, communication, refrigeration, medical routines, or work continuity. Record running watts, startup watts, daily hours, and priority before adding comfort devices. Use current primary documentation, measured loads, and a tested recharge and fallback plan before relying on the system.

Last materially reviewed 2026-08-28

Quick answerList only the loads that protect safety, communication, refrigeration, medical routines, or work continuity. Record running watts, startup watts, daily hours, and priority before adding comfort devices.
Direct answer

Critical-load audit: start with a measured brief

List only the loads that protect safety, communication, refrigeration, medical routines, or work continuity. Record running watts, startup watts, daily hours, and priority before adding comfort devices.

A sound critical-load audit decision has four boundaries: the load that must run, the hours it must survive, the method and time available to replenish it, and the fallback if either assumption fails. Build three tiers: keep alive, restore soon, and leave off. For each device, capture the label, a plug-meter observation where suitable, compressor or motor behavior, realistic daily use, and the person authorized to shed it. The tier order becomes the outage operating script.

  • Build three tiers: keep alive, restore soon, and leave off. For each device, capture the label, a plug-meter observation where suitable, compressor or motor behavior, realistic daily use, and the person authorized to shed it. The tier order becomes the outage operating script.
How it works

Build the operating sequence

Translate specifications into a day of operation. Note startup events, idle draw, duty cycle, temperature, simultaneous loads, reserve, charging windows, and what happens after a cloudy day or missed drive.

Record the one uncertain fact that could reverse the choice. That becomes the next measurement or support question.

  • Measure the actual load.
  • Verify the exact model and connection.
  • Record the fact that would reverse the decision.
Decision framework

Stress-test the weakest condition

Stress-test the worst credible condition: cold batteries, hot charging, a compressor start, longer runtime, shade, a missed recharge window, an added medical or communication load, or a person unfamiliar with the system.

Keep a fallback with a different failure mode and never use a consumer battery as the only protection for a high-consequence load.

  • Compare the same power job.
  • Keep runtime and recharge in one model.
  • Protect a fallback with a different failure mode.
Final check

Record the plan before relying on it

Assign the next action and date. One person should own charging, inspection, updates, testing, and storage, while everyone who may use the unit knows the safe connection and shutdown sequence.

Retest before storm season, travel, or a critical event. Reliability is a practiced workflow, not a battery percentage on the day it is needed.

  • Save the manual and load record.
  • Assign the system owner.
  • Retest before relying on it.
Continue when useful

Next: Runtime formula

Estimate runtime by multiplying rated watt-hours by a conservative usable fraction, then dividing by the measured average load in watts. Treat the result as a planning range, not a promise. Use current primary documentation, measured loads, and a tested recharge and fallback plan before relying on the system.

Open Runtime formula →
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Related guides

Runtime formulaEstimate runtime by multiplying rated watt-hours by a conservative usable fraction, then dividing by the measured average load in watts. Treat the result as a planning range, not a promise. Use current primary documentation, measured loads, and a tested recharge and fallback plan before relying on the system.LiFePO4 batteryLithium iron phosphate is a lithium-ion chemistry used in many current portable stations. Chemistry is one part of a safe system; enclosure, controls, certifications, charging design, and use conditions still matter. Use current primary documentation, measured loads, and a tested recharge and fallback plan before relying on the system.AC70The AC70 belongs on a shortlist when its current capacity, inverter output, charging limits, weight, and port mix align with a modest mobile or outage load plan. Use current primary documentation, measured loads, and a tested recharge and fallback plan before relying on the system.

Sources used for this page

These records support the facts and comparisons above. Merchant-controlled records are labelled so you can separate product claims from independent evidence.

  1. Ready.gov power outage guidance — GOVERNMENT · checked 2026-08-28
  2. US Department of Energy solar and resilience basics — GOVERNMENT · checked 2026-08-28