For DIY mini-split shoppers

Size, compare and cost a mini-split by the numbers

Capacity, SEER2, HSPF2, line-set limits and electrical ratings from manufacturer spec sheets, plus sizing and refrigerant rules from DOE, ENERGY STAR and the EPA. Every figure links to its source.

Start with the buyer’s guide Estimate running cost

Photo: a bright modern living room with a plain white unbranded ductless mini-split indoor unit mounted high on the wall, soft daylight, minimal furniture. Photorealistic, no logos, no brand names, no text

Before you buy a “DIY” kit: EPA says connecting or disconnecting pre-charged lines on a mini-split requires Section 608 technician certification. Read what the rule covers.

Start here

Sizing a room, comparing models, or planning the install: pick your starting point.

Photo: a plain white unbranded wall-mounted mini-split indoor unit above a window in a tidy bedroom, an open product box and manual on the floor. Photorealistic, no logos, no brand names, no textChoosing a SystemDIY Mini-Split Buyer's Guide 2026How to choose a DIY mini-split in 2026: sizing with Manual J, reading SEER2 and HSPF2, cold-climate ratings, line sets, wiring, EPA…Photo: a home office with a plain white wall-mounted mini-split head, a tape measure and a notepad with a simple floor sketch on the desk. Photorealistic, no logos, no brand names, no textChoosing a SystemWhat Size Mini-Split Do I Need?How to size a mini-split: why ENERGY STAR and DOE point to an ACCA Manual J load calculation, why oversizing hurts, and…Photo: close-up of a generic blank yellow energy rating label style card next to a plain white mini-split remote control on a wooden table, no readable text. Photorealistic, no logos, no brand names, no textChoosing a SystemSEER2, EER2 and HSPF2 Explained for Mini-Split BuyersWhat SEER2, EER2 and HSPF2 mean, why they replaced SEER and HSPF in 2023, why the numbers are lower, and how to…Photo: a plain unbranded outdoor mini-split condenser on a wall bracket beside a house in snow, frost on the fins, winter morning light. Photorealistic, no logos, no brand names, no textChoosing a SystemCold-Climate Mini-SplitsWhat makes a mini-split cold-climate: ENERGY STAR's COP of at least 1.75 at 5°F and 70% capacity retention, low-temperature operating limits, and…Photo: three plain unbranded white outdoor heat pump condensers of increasing size lined up on a concrete pad against a gray siding wall. Photorealistic, no logos, no brand names, no textComparisonsMRCOOL DIY 5th Gen Sizes ComparedMRCOOL DIY 5th Gen single-zone sizes side by side: SEER2, EER2, HSPF2 Region IV and V, line sizes, refrigerant charge and the…Photo: a technician in work gloves connecting refrigerant line fittings to a plain unbranded outdoor condenser service valve with a wrench, close-up. Photorealistic, no logos, no brand names, no textInstallationCan You Install a Mini-Split Yourself?What EPA says about DIY mini-split installation: Section 608 certification for connecting pre-charged lines, what counts as opening the refrigerant circuit, and…

The short version

  1. Size from a load calculationENERGY STAR and DOE point to ACCA Manual J, not square footage. How to size
  2. Compare HSPF2 for heatingIn cold climates, check capacity at 5°F too. Cold-climate criteria
  3. Do the cost mathHeat needed ÷ HSPF2 × your rate. Operating cost calculator

Choosing a System

All choosing a system

Sizing, efficiency ratings and cold-climate performance.

Photo: a plain white unbranded wall-mounted mini-split indoor unit above a window in a tidy bedroom, an open product box and manual on the floor. Photorealistic, no logos, no brand names, no textChoosing a SystemDIY Mini-Split Buyer's Guide 2026Photo: a home office with a plain white wall-mounted mini-split head, a tape measure and a notepad with a simple floor sketch on the desk. Photorealistic, no logos, no brand names, no textChoosing a SystemWhat Size Mini-Split Do I Need?Photo: close-up of a generic blank yellow energy rating label style card next to a plain white mini-split remote control on a wooden table, no readable text. Photorealistic, no logos, no brand names, no textChoosing a SystemSEER2, EER2 and HSPF2 Explained for Mini-Split BuyersPhoto: a plain unbranded outdoor mini-split condenser on a wall bracket beside a house in snow, frost on the fins, winter morning light. Photorealistic, no logos, no brand names, no textChoosing a SystemCold-Climate Mini-Splits

Comparisons

All comparisons

Models and system layouts compared from spec sheets.

Photo: three plain unbranded white outdoor heat pump condensers of increasing size lined up on a concrete pad against a gray siding wall. Photorealistic, no logos, no brand names, no textComparisonsMRCOOL DIY 5th Gen Sizes ComparedPhoto: cutaway-style illustration of a two-story house with several plain white wall-mounted indoor units in different rooms and condensers outside, clean flat style, no text. Photorealistic, no logos, no brand names, no textComparisonsSingle-Zone vs Multi-Zone Mini-Splits

Installation

All installation

Line sets, electrical and the EPA rules on refrigerant work.

Photo: a coiled insulated copper refrigerant line set with white insulation lying on a garage floor next to a tape measure. Photorealistic, no logos, no brand names, no textInstallationMini-Split Line Set LengthPhoto: a technician in work gloves connecting refrigerant line fittings to a plain unbranded outdoor condenser service valve with a wrench, close-up. Photorealistic, no logos, no brand names, no textInstallationCan You Install a Mini-Split Yourself?Photo: a gray outdoor electrical disconnect box mounted on a house wall next to a plain unbranded mini-split condenser, conduit running between them. Photorealistic, no logos, no brand names, no textInstallationMini-Split Electrical Requirements

Costs & Rules

All costs & rules

Operating cost, tax credits and refrigerant rules.

Photo: two plain unlabeled refrigerant cylinders, one pink and one gray, standing on a workshop floor beside a manifold gauge set, no readable text. Photorealistic, no logos, no brand names, no textCosts & RulesR-410A vs R-454B and R-32Photo: a desk with a calculator, a generic paper form with no readable text, a pen and a small model house, soft natural light. Photorealistic, no logos, no brand names, no textCosts & RulesHeat Pump Tax Credit in 2026Photo: a plain white mini-split remote control, a calculator and a generic utility bill with no readable text on a kitchen counter. Photorealistic, no logos, no brand names, no textCosts & RulesMini-Split Operating Cost

Sourced, not guessed

Specs come from manufacturer documents; sizing and rules from DOE, ENERGY STAR, AHRI and the EPA. Every page links its sources.

Research, not test claims

We compile published specs and manuals. We don’t run our own equipment tests, and we never claim we did.

Independent

Where we may earn a commission, we say so. Commissions never decide a recommendation.

Printed from https://minisplitmath.com/ · Mini Split Math (minisplitmath.com). Sources are listed on the page.