Our Technical Verification Methodology
At BackupWattGuide, our mission is to eliminate dangerous guesswork and unrealistic marketing runtimes through rigorous electrical engineering load calculations.
Why BackupWattGuide Was Founded
Commercial portable power station manufacturers routinely market runtimes based on theoretical laboratory conditions: 100% discharge depth, unity power factor loads, zero ambient thermal degradation, and zero inverter quiescent (idle) power draw.
In emergency scenarios—such as running a basement sump pump during a storm or keeping critical medical refrigeration active during a blackout—miscalculating runtime by even 25% can lead to catastrophic property loss or personal injury. We publish empirical, conservative, and mathematically verified specifications so homeowners, solar technicians, and off-grid engineers have real numbers they can count on.
The Three Pillars of Our Sizing Math
Electrical Load Math
We calculate real continuous draw using True RMS current, apparent power ($VA$), and reactive inductive power factors ($PF = 0.75 - 0.90$) rather than optimistic label wattages.
FLA / LRA Surge Analysis
Electric motors (sump pumps, compressor refrigerators, power tools) require Locked Rotor Amps (LRA) on startup, drawing 3× to 6× their nameplate Full Load Amps (FLA) for 200–500ms.
85% Inverter Model
DC-to-AC pure sine wave inverters lose 10–15% energy in DC conversion losses and standby electronics. We standardize on an empirical 85% usable battery throughput ceiling.
The Continuous Runtime Formula
All runtime guides and interactive calculators on BackupWattGuide are governed by the following formula:
// Inverter-Adjusted Usable Runtime Formula
Runtime (Hours) = (Battery Nominal Wh × 0.85) / (Continuous Appliance Watts + Inverter Idle Draw) Where:
- Battery Nominal Wh is the stated watt-hour capacity of the Lithium Iron Phosphate (LiFePO4) or NMC battery pack.
- 0.85 (85%) accounts for DC-to-AC conversion loss, BMS low-voltage cut-off protection, and battery internal resistance.
- Inverter Idle Draw accounts for the inverter's active gate drivers, fans, and display electronics (typically 12W to 35W depending on inverter class).
Editorial Independence & Technical Integrity
BackupWattGuide operates under strict editorial independence. Our engineering analysis is designed strictly to educate homeowners and electrical hobbyists on safe, compliant portable power practices. We do not accept sponsored product placements that alter our mathematical evaluations or safety recommendations.
Questions or Technical Feedback?
If you have spotted a typo, wish to propose an appliance benchmark, or have a question regarding an inverter error code, reach out directly via our Technical Inquiry Form.