The leaders by size
| Size | Highest cooling efficiency (SEER2) | Close behind |
|---|---|---|
| 6k | Carrier Infinity 35 6k 230V: 35.1 | Mitsubishi Electric M-Series FX Deluxe Hyper-Heat 6k 230V and Blueridge XS6 Max Efficiency 6k 230V: 35 |
| 9k | Fujitsu AIRSTAGE Orion XLTH+ 9k 230V and Carrier Infinity 35 9k 230V: 33.5 | Senville ELITE Series 9k 230V and Blueridge XS6 Max Efficiency 9k 230V: 33.3 |
| 12k | Fujitsu AIRSTAGE Orion XLTH+ 12k 230V: 31.5 | Fujitsu AIRSTAGE Orion XLTH 12k 230V: 30.5, Mitsubishi Electric M-Series FX Deluxe Hyper-Heat 12k 230V: 29.9 |
| 18k | GREE Sapphire R32 18k 230V: 27.5 | Fujitsu AIRSTAGE H-series 18k 230V: 26.3, Carrier Infinity 35 18k 230V: 25.8 |
| 24k | GREE Sapphire R32 22k 230V: 27 | GREE Vireo R32 22k 230V: 26, Senville ELITE Series 24k 230V: 25 |
These are the certified ratings, not marketing "up to" numbers. A higher SEER2 means lower cooling bills.
What "efficient" actually means here
- SEER2 is the cooling rating over a whole season. Higher means less electricity for the same cooling.
- EER2 is cooling efficiency on the hottest afternoons, at full power.
- HSPF2 is the heating version of SEER2. It's the one that matters most if you'll heat with the system.
A more efficient system costs more up front and pays some of that back on your bill, so the most efficient pick isn't automatically the best value. Run the operating-cost calculator and the payback calculator with your own electricity rate before paying for the top rating.
Most efficient you can buy online: Senville ELITE and Blueridge XS6
The Senville ELITE Series 9k 230V and the Blueridge XS6 Max Efficiency 9k 230V are rated identically at 9,000, 12,000 and 18,000 BTU. They're the pick if you want near-top efficiency, the best heating ratings in this guide, and a system you can order online. At 18,000 BTU they share the highest heating efficiency we list, with Carrier's Infinity 35, and every size keeps heating down to -22F. Senville sells direct and Blueridge sells through Alpine Home Air; both need a professional install.
Most efficient premium: Mitsubishi FX, Fujitsu Orion XLTH+ and Carrier Infinity 35
These three sell through dealers, and they sit at the very top of the ratings:
- The Mitsubishi Electric M-Series FX Deluxe Hyper-Heat 6k 230V is the most efficient system we list on the hottest afternoons, and near the top of the seasonal ratings too. The FX line stays near the top up to 12,000 BTU.
- The Fujitsu AIRSTAGE Orion XLTH+ 12k 230V is the most efficient 12,000 BTU system we list, for cooling and for heating.
- The Carrier Infinity 35 6k 230V has the highest cooling rating of all.
Fujitsu and Carrier don't honor online purchases under their warranties, so get these through a dealer quote.
Most efficient big name online: Gree Sapphire
Gree's Sapphire is the most efficient system we list at 18,000 and 24,000 BTU, and near the top at 12,000. You can buy it at HVACDirect, but Gree attaches conditions to online purchases, so buy from a seller Gree authorizes. Its heating rating trails the Senville and the Blueridge, so it suits homes that mostly need cooling.
Multi-zone runs lower
Sharing one outdoor unit across several rooms costs efficiency. The most efficient multi-zone system we list is the Della Optima Pro CloudAir Series Multi-Zone 20k 230V, and the rest of the field is in best multi-zone mini splits.
How we picked
We use the certified ratings, or the manufacturer's published number where there's no certificate. We compare within a size, because setting a 6,000 BTU system against a 24,000 BTU one tells you little about the system you'll actually buy. No brand pays for placement.
Efficient doesn't always mean cheapest to own
The highest rating isn't automatically the lowest lifetime cost. Your electricity rate, your climate and how many hours the system runs all matter, and a mid-range system in a mild climate can beat a premium one you overpaid for. Work out your own numbers:
- Operating-cost calculator - the monthly bill for a given efficiency and rate.
- Payback calculator - when the premium pays for itself.
- Electricity usage guide - what drives the bill.
FAQ
What is the most efficient mini split? The smallest ones. 6,000 BTU systems from Carrier, Mitsubishi and Blueridge top the ratings. At the common 12,000 BTU size, Fujitsu's Orion XLTH+ leads.
What's the most efficient mini split you can buy online? The Blueridge XS6 6k, sold through Alpine Home Air, is at the top of the ratings. At 9,000 BTU the Senville ELITE and Blueridge XS6 sit just behind the dealer-only leaders, and at 18,000 and 24,000 BTU Gree's Sapphire leads outright.
Does a higher SEER2 mini split save money? It uses less electricity per season, but whether it saves you money depends on your rate, your climate and how much it runs. Check the payback calculator.
Is SEER2 or HSPF2 more important? SEER2 if you mostly cool, and HSPF2 if you heat a lot, which in a cold climate usually means HSPF2. The best heating ratings we list belong to the 18,000 BTU Senville ELITE, Blueridge XS6 and Carrier Infinity 35.
Sources
- Air-Conditioning, Heating, and Refrigeration Institute: AHRI Appendix M1 public detail for BXS6A06UC0 / BXS6A06WM0 - Blueridge XS6 Max Efficiency 6,000 BTU R-454B 208/230V (BXS6A06WM0 / BXS6A06UC0), retrieved Jul 24, 2026.
- Blueridge / Alpine Home Air Products: Flared line set and professional startup evidence - Blueridge XS6 Max Efficiency 6,000 BTU R-454B 208/230V (BXS6A06WM0 / BXS6A06UC0), retrieved Jul 24, 2026.
- Blueridge / Alpine Home Air Products: Flared line set and professional startup evidence - Blueridge XS6 Max Efficiency 6,000 BTU R-454B 208/230V (BXS6A06WM0 / BXS6A06UC0), retrieved Aug 17, 2026.
- Blueridge / Alpine Home Air Products: Flared line set and professional startup evidence - Blueridge XS6 Max Efficiency 6,000 BTU R-454B 208/230V (BXS6A06WM0 / BXS6A06UC0), retrieved Aug 29, 2026.
- ENERGY STAR: ENERGY STAR exact row check for AHRI 216997533 - Blueridge XS6 Max Efficiency 6,000 BTU R-454B 208/230V (BXS6A06WM0 / BXS6A06UC0), retrieved Jul 24, 2026.
- Air-Conditioning, Heating, and Refrigeration Institute: AHRI Appendix M1 public detail for BXS6A09UC0 / BXS6A09WM0 - Blueridge XS6 Max Efficiency 9,000 BTU R-454B 208/230V (BXS6A09WM0 / BXS6A09UC0), retrieved Jul 24, 2026.
- Alpine Home Air Products: Blueridge BXS6A09UC0-9WM Alpine product specification grid - Blueridge XS6 Max Efficiency 9,000 BTU R-454B 208/230V (BXS6A09WM0 / BXS6A09UC0), retrieved Jul 24, 2026.
- Blueridge / Alpine Home Air Products: Flared line set and professional startup evidence - Blueridge XS6 Max Efficiency 9,000 BTU R-454B 208/230V (BXS6A09WM0 / BXS6A09UC0), retrieved Aug 17, 2026.
- Blueridge / Alpine Home Air Products: Flared line set and professional startup evidence - Blueridge XS6 Max Efficiency 9,000 BTU R-454B 208/230V (BXS6A09WM0 / BXS6A09UC0), retrieved Aug 29, 2026.
- ENERGY STAR: ENERGY STAR exact row check for AHRI 216997533 - Blueridge XS6 Max Efficiency 9,000 BTU R-454B 208/230V (BXS6A09WM0 / BXS6A09UC0), retrieved Jul 24, 2026.
- Air-Conditioning, Heating, and Refrigeration Institute: AHRI Appendix M1 public detail for 37MPRAQ18AA3 / 45MPHAQ18XA3 - Carrier Infinity 35 18,000 BTU R-454B 208/230V (45MPHAQ18XA3 / 37MPRAQ18AA3), retrieved Jul 27, 2026.
- Carrier Corporation: Carrier Infinity 35 Mini Split Heat Pump with Basepan Heater - Carrier Infinity 35 18,000 BTU R-454B 208/230V (45MPHAQ18XA3 / 37MPRAQ18AA3), retrieved Jul 27, 2026.