About GeneratorSizingPro

Our Mission

GeneratorSizingPro exists to give homeowners the information they need before calling a dealer. A backup generator is a major purchase — often $1,000 to $15,000 or more installed — but most people go into the decision with no way to independently check whether the size and price they're being quoted actually make sense. We fix that.

Every calculator on this site is built around real electrical formulas: running and starting (surge) watts by appliance, NEC transfer switch requirements, altitude derating factors, and realistic regional installation cost ranges. Our tools give you a solid estimate in under a minute so you can walk into a conversation with a dealer already informed.

What We Offer

Five free calculators covering the questions homeowners ask most often:

• Generator Wattage Sizing Calculator — running + starting watts across 30+ appliances, with custom load support
• Whole-House Sizing Calculator — standby size by panel amperage, central AC, and altitude
• Fuel Runtime & Cost Calculator — how long a tank lasts and what it costs across fuel types
• Standby vs. Portable Cost Calculator — full total-cost-of-ownership comparison
• Installation Cost Estimator — itemized breakdown of equipment, pad, transfer switch, gas line, and labor

Who We Are

GeneratorSizingPro is a property of Berean Defense L.L.C., a Wyoming LLC focused on building practical, data-driven tools for homeowners and consumers. We are not affiliated with any generator manufacturer, dealer network, or installation company. Our calculations are based on industry standards, NEC code requirements, and publicly available cost data.

Our Methodology

Every calculator on this site is built from the same set of sourced, defensible inputs rather than a black-box formula:

• Running and starting (surge) watts for common household appliances and motors, reflecting the well-established engineering principle that motor-driven loads draw a brief surge — typically 2 to 3 times running watts — when they start.
• National Electrical Code Article 702 for transfer switch requirements, since any generator connected to a home's wiring must isolate the home from the utility grid to prevent backfeeding.
• A ~3% output-loss-per-1,000-ft altitude derating factor, the standard rule of thumb for how thinner air at elevation affects combustion-engine output.
• Typical industry cost bands for equipment, transfer switches, pad work, fuel connections, labor, and permits, presented as ranges rather than a single manufactured "exact" price, since real installed cost depends on your specific site, region, and installer.

Every calculator states its assumptions directly next to the result, and every result is labeled as an estimate — never a substitute for a licensed electrician's or installer's assessment of your specific home.

Editorial Policy

GeneratorSizingPro does not accept payment to influence a calculator's math, and no calculator's recommended size or cost range is ever adjusted based on which products, dealers, or affiliate programs the site does or doesn't participate in. As of this page's last review, the site does not yet run Amazon Associates links, dealer-referral links, or display advertising — when any of those are added, they will be clearly labeled and disclosed on the page where they appear, and on a dedicated affiliate disclosure page, consistent with FTC guidance on affiliate marketing disclosures.

Review & Updates

This site's methodology, calculators, and guides are maintained by the Berean Defense L.L.C. team. Content is reviewed periodically against current NEC guidance and general industry pricing patterns; each calculator and guide page lists its own "last reviewed" date. This page last reviewed: August 2026. Spot something outdated or think we got a figure wrong? Use the Contact page — corrections are welcome and reviewed promptly.

Disclaimer

All results produced by our calculators are estimates based on industry rules-of-thumb and regional averages. Actual generator sizing, installation costs, and fuel consumption vary based on factors not captured by any online tool. Always obtain quotes from licensed electricians and generator installers before purchasing. See our full disclaimer for details.