About

Why Splitsizer exists

Heat-pump research gets messy fast. A homeowner starts with one simple question, "What size do I need?", and ends up juggling square footage, climate, insulation, ceiling height, rebates, electrical work, and installer quotes. Splitsizer keeps the first step narrow: estimate a practical BTU range before you compare equipment.

Splitsizer is brand-neutral. We do not manufacture heat pumps or sell equipment directly. The calculator starts with the shape of your project, returns a first-pass size range, and points out when the job is large enough to justify a formal load calculation.

Who runs Splitsizer

One independent operator, working on Splitsizer as a side project. No HVAC license, no manufacturer relationships, no sponsored placements, no paid editorial slots. The site exists because the existing online sizing tools are either retailer-owned (and biased toward their house brands) or single-input thermometers that don't account for the variables that actually move the BTU number.

Calling that "expertise" would be misleading — Splitsizer is a research and screening tool, not a substitute for a licensed contractor's load calculation. The site goes to lengths to flag that distinction on every output: in the calculator's methodology note, in each guide's footer, in every state rebate page's "before you apply" section. The rule of thumb: any single-room install can reasonably be sized from a screening calculator; any whole-home or cold-climate install should be confirmed with a Manual J load calculation by a qualified installer before equipment is purchased.

The sizing methodology

The calculator uses a BTU-per-square-foot baseline with adjustments for climate band, insulation, sun exposure, and ceiling height. The math is transparent because it's deliberately simple — every input is a real factor that moves the load, but the model is materially less sophisticated than ACCA Manual J. Treat it as a screening number.

The math, step by step

1. Base load: square footage × 20 BTU/hour. A 600 sq ft room starts near 12,000 BTU; a 1,000 sq ft open area starts near 20,000 BTU.
2. Climate band: warm × 0.9, mixed × 1.0, cold × 1.2. Cold climates need more heating capacity at the design temperature; warm climates need less.
3. Insulation: poor × 1.25, average × 1.0, excellent × 0.85. Older homes and homes with unsealed envelopes lose conditioned air faster.
4. Sun exposure: shaded × 0.9, average × 1.0, heavy sun × 1.2. West and south-facing rooms with large glass run materially higher cooling loads.
5. Ceiling height: 8 ft × 1.0, 9 ft × 1.1, 10 ft or vaulted × 1.2. More air volume to condition.
6. Output range: result × 0.92 to result × 1.08, rounded to the nearest 100 BTU. The range communicates the screening-level uncertainty.
7. Snapped to standard sizes: 6,000 / 9,000 / 12,000 / 18,000 / 24,000 / 30,000 / 36,000 / 48,000 BTU. Mini splits and central heat pumps are sold in these classes; the useful question is which class the project lands in, not a decimal-precise BTU figure.

What the model does not account for: window U-values, room orientation, internal heat gain from electronics or appliances, infiltration rate, and design temperature for the specific ZIP code. ACCA Manual J accounts for all of these — which is why whole-home installs need it.

Editorial standards

Product recommendations map to a buyer profile (DIY-friendly, budget pro-install, cold-climate) and a size class. The recommendation logic is the same whether or not a product has an active Amazon listing — products without an affiliate path are still included when they're the right call.

• Affiliate links are disclosed on every page and in the footer. Amazon links carry the splitsizer-20 tag; outbound links use rel="sponsored noopener nofollow" per Amazon Associates and FTC guidance.
• No manufacturer money. Splitsizer does not accept payment, free product, or promotional consideration from any heat pump or mini split manufacturer.
• Rebate amounts are cross-referenced against official program pages (DSIRE, state energy office sites, utility rebate pages) at the date listed on each rebate page. Programs change — verify before applying.
• Installer lead-gen forwards your details only to installers partnered in your ZIP. If no partner is active in your area, Splitsizer texts back personally as soon as one is available. The form copy is explicit about that.
• Update timestamps on every detail page show when the content was last reviewed. Pages without an explicit update date have not been substantively edited since first publication.

Sources

• DSIRE — Database of State Incentives for Renewables & Efficiency. Primary cross-reference for state and utility rebate programs.
• US DOE Home Energy Rebates — Federal IRA program tracker (HEEHRA and HOMES).
• ENERGY STAR federal tax credits — Reference for 25C (ended Dec 31 2025) and 25D (geothermal, active through 2032).
• Manufacturer product pages — Mr Cool, Pioneer, Senville, Della, Cooper & Hunter, Mitsubishi, Daikin for specifications, capacity tables, and warranty terms.
• ACCA Manual J Abridged Edition — Methodological reference for the BTU-per-square-foot baseline and adjustment factors. Splitsizer's model is intentionally simpler than a full Manual J but follows the same input categories.

Boundaries

• The calculator is a screening tool, not a full HVAC design.
• The output appears in the browser without an email signup.
• Manufacturer payments do not control placement.
• Rebates and tax credits need to be verified against official rules for your project date and location.
• Single-room installs can reasonably be sized from this calculator; whole-home and cold-climate installs should be confirmed with a Manual J load calculation by a qualified installer.

Contact

Found something wrong, missing, or out of date? Email hello@splitsizer.com and it gets fixed. Same address for affiliate questions, rebate program corrections, or installer partnership inquiries.