Methodology

1. Situation before hardware

Every evaluation begins with a declared use case — home outage, 72-hour family readiness, fridge and freezer, router and PC, CPAP, van or RV, jobsite, outdoor. Brand is never an entry point, and brand plays no role in ranking.

2. Load modeling

Loads come from an appliance library combined with user input. For each device the engine needs continuous watts, startup peak, hours of use, whether it runs at the same time as other devices, and its priority level.

• Continuous watts drive energy consumption over time.
• Startup peak is a separate pass/fail gate on inverter output.
• Simultaneity determines the worst-case concurrent draw.
• Priority decides what is protected when something must be dropped.

Runtime is never derived from nominal watt-hours alone. A label figure is an upper bound under manufacturer test conditions, not delivered energy.

3. Energy need

The required energy is built up conservatively, in this order:

• Target duration for the declared scenario.
• Energy demanded by the prioritized load set across that duration.
• Conversion and inverter losses applied against the user.
• A safety reserve retained rather than spent.
• Required continuous output and required peak output, evaluated separately.

Calculations are deterministic: identical declared inputs always produce an identical result, and every intermediate figure is shown.

4. Recharge

A power architecture must survive a complete use-and-recharge cycle. The engine takes the available recharge paths (wall, solar, vehicle), the time actually available, whether pass-through or UPS behavior is needed, and whether expansion is possible. Architectures that cannot close the cycle are eliminated, regardless of capacity.

5. Constraints

Budget, weight, noise, portability, indoor or outdoor use, temperature range, connector requirements and warranty are hard filters, not preferences to be traded away silently. A constraint may eliminate a higher-capacity model, and when it does, the verdict says so.

6. Dated catalog policy

The catalog separates stable specifications from volatile commercial data.

• Specification record: estimated usable capacity, continuous and peak watts, wall and solar recharge, UPS / pass-through behavior, expansion options, weight, warranty — each with a source reference and an evidence-quality rating.
• Commercial record: price and stock, always time-stamped, never merged into the specification record and never presented as current unless it is.
• Unknown is a value. Missing, unknown, zero, not applicable and contradictory are distinct states and render differently.

7. Verdicts

Where justified, the engine returns three to five outputs — best fit, lower cost, lighter, expandable — each with the reasons that produced it and the limits that qualify it. When the declared peak, duration, recharge window and constraints cannot be satisfied together, the output is an explicit no-fit abstention. Abstention is a valid answer, and it is displayed differently from a rational “buy nothing yet” conclusion.

8. Limits of this method

• Outputs are only as good as the declared inputs; bad load estimates produce bad sizing.
• Real appliances vary from library averages, especially older compressors and motors.
• Solar figures depend on conditions this system cannot observe.
• Nothing here is electrical, safety, medical or financial advice, and no performance guarantee is made. For life-supporting equipment, follow the manufacturer and your clinician.

Rule changes and corrections are logged on the updates page.