How we research, write, and review every recommendation.

1. Who writes for WhatSize

Content is produced by the WhatSize editorial team — a small group of writers, researchers, and product analysts who specialize in appliance sizing standards. Every page carries a byline to the team, not to an individual contributor, because recommendations are reviewed and signed off collectively before publication.

Our research process is based on:

• Direct analysis of public industry standards — AHAM, DOE, ACCA, and NEC — for every calculator formula and sizing recommendation
• Review of manufacturer spec sheets and published performance curves for verified wattage, BTU, and pumping data
• Cross-referencing multiple independent sources before any recommendation is published
• Regular re-review against updated editions of cited standards

2. Our sources

Every sizing formula and recommendation on this site is sourced to a public, named standard. We do not invent formulas, do not copy from anonymous blog posts, and do not rely on unverified claims.

The primary sources we cite:

• ANSI/AHAM AC-1 — Air Cleaner CADR Performance Standard (Association of Home Appliance Manufacturers)
• ANSI/AHAM DH-1 — Dehumidifier Performance Standard (current edition: DH-1-2022)
• 10 CFR Part 430 — DOE Energy Conservation Standards for Consumer Products (water heater FHR, appliance capacity)
• ACCA Manual J (8th Edition) — Residential HVAC Load Calculation
• NFPA 70 / NEC Articles 701 & 702 — National Electrical Code: Legally Required Standby (701) and Optional Standby (702, used for residential generator sizing)
• EPA Indoor Air Quality guidance for residential air cleaners
• ENERGY STAR product specifications for dehumidifiers, air purifiers, water heaters, and mini splits
• AHRI Directory — certified performance ratings for HVAC equipment
• Manufacturer spec sheets and published performance curves (Generac, Honda, Champion, Zoeller, Wayne, MrCool, Bosch, Rheem, Levoit, Frigidaire, DELLA) for verified wattage, BTU, and pumping performance

3. Editorial workflow

Every calculator and guide goes through a four-step review before publication:

1. Research. The lead writer pulls the relevant standard (e.g. AHAM DH-1 for dehumidifiers), reads the full current edition, and identifies the exact formula or methodology that will drive the calculator.
2. Draft. Calculator logic is implemented in code; guide copy is drafted. A second team member reviews the formula against the source standard line-by-line.
3. Test. Calculator outputs are spot-checked against known manufacturer reference cases (e.g. AHAM-verified CADR for a Levoit Core 300 in a 200 sq ft room). Any deviation above 5% triggers a re-review.
4. Sign-off & publish. A senior reviewer signs off, the page is published, and the “Last reviewed” date is recorded.

4. How calculators are built

Every calculator is deterministic — same inputs always produce the same output. Formulas, safety margins, and lookup tables are visible to the user inside the “How we calculated this” expandable section on every result. No calculator uses machine learning, black-box estimates, or undisclosed multipliers.

Where a standard allows engineer judgment (e.g. Manual J climate zone factors), we cite the specific table and edition used and apply the published value directly. Where no public standard exists (e.g. sump pump GPH for residential pits), we publish the underlying performance curves and disclose the manufacturer source for each datapoint.

5. Product recommendation policy

Recommended products are picked by the editorial team based on four weighted criteria, in this order:

1. Verified specifications. The product meets or exceeds the calculator's required output (BTU, CADR, GPH, watts, FHR).
2. Independent reviews & reliability data. We consult consumer review aggregators and recall databases. A product with an active CPSC recall is removed immediately.
3. Availability. The product is in stock and ships from a major US retailer at the time of last review.
4. Value. Among qualifying products, we favor the lower price. We do not favor higher-priced products because of higher affiliate commission.

WhatSize Appliance is a participant in the Amazon Services LLC Associates Program — an affiliate advertising program. Commissions never influence which products make a list. The full disclosure is on our About page.

6. Update & review cadence

• Standards re-checked quarterly. AHAM, DOE, ACCA, and NEC publish errata and updates; we review each cited standard at least every 90 days.
• Calculator logic re-validated annually against the latest published test data.
• Product lists re-curated monthly. Out-of-stock products, discontinued models, and superseded versions are removed; new qualifying products are added.
• A "Last reviewed" date appears on every calculator and guide. The date reflects the most recent substantive review, not an automated rebuild.

7. Corrections policy

We make mistakes. When a reader reports a calculation error, factual inaccuracy, or broken recommendation, we follow this process:

1. The report is logged and acknowledged within 2 business days via email.
2. The editor verifies the report against primary sources.
3. Confirmed errors are corrected within 5 business days; the page is republished and a correction note is added at the bottom of the affected page.
4. Material errors that could have led a user to buy the wrong-sized product are escalated for a same-day fix and a public note.

To report a suspected error, email [email protected] with the page URL and a description.

8. Conflicts of interest

The WhatSize editorial team does not accept payment, free product, or favors from appliance manufacturers in exchange for coverage. Affiliate commissions from Amazon are disclosed on every page that links to a product, and they do not influence selection. Team members with any personal financial interest in a manufacturer (e.g. an immediate family member employed there) are recused from reviewing that manufacturer's product line.