the bill · deep dive
The Mini-Split
Three picks, two funerals, and a discontinued flagship later, the office gets 120V, a Gree-built brain Home Assistant already speaks natively, and a flare-and-vacuum install that's more honest work than the quick-connect marketing wants you to believe. This part is fully decided — the whole page is the receipt.
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The Rundown
8 items · ≈$950 all-in · updated jul 18 2026
- ◆ decided The pick: TOSOT Cosmo 9k, 120V — $595 w/ SUMMER15 ($700 list) — the third pick, after two funerals (a discontinued Mitsubishi FS09, then a $2,652 FX09 sticker shock).
- ◆ decided 120V is the circuit: a dedicated 20A run on 12 AWG at the condenser — the last argument for 240V left with Mitsubishi's hyper-heat catalog.
- ◆ decided The install is standard flare-and-vacuum: torque to the manual's table, pull to 500 microns, bubble-test every joint — no quick-connect shortcuts and none needed.
- ◆ decided Tools run ~$250, reusable for the next job; all-in with the unit, the electrical bits, and a lineset cover kit — ~$850–900.
- ◆ decided R32, precharged, 5-year warranty whose bar is "per the manual and local codes" — DIY-legal, not DIY-optional.
The Saga
three picks, two funerals
Three picks, two funerals. The first was the Mitsubishi MSZ-FS09NA — hyper-heat, CN105-moddable, and anchored to a $775 clearance condenser that turned out to be too good to be true: the matching indoor head was discontinued everywhere, the cheap condenser an orphan. Lesson banked — stock-check clearance before it becomes the plan. The pivot was the FX09, and the FX09 survived its stock check and died at the checkout: $2,652 is flagship money for a 169-sqft office with a working gas furnace already standing behind it. That's when the search stopped chasing a badge and started chasing the field — a July 18 sweep of Mr Cool, TOSOT, Senville, Pioneer, Della, Klimaire, and Fujitsu — and found something better than a consolation prize.
The Pick
the office · 120V · decided, third time honest
A unit at a fifth of the FX09's price with a cleaner local-control story than the CN105 solder mod: built-in WiFi that Home Assistant's native Gree integration drives over local UDP, documented in TOSOT's own Home Assistant guide. One cloud touch to bind WiFi at setup, then LAN-only forever. No dongle, no soldering, no Kumo.
TOSOT Cosmo 9k, 120V GWH09AWCXB-A6DNA1AI / GWH09ATCXB-A6DNA1AO — $595 w/ SUMMER15 · $700 list. Gree-built (TOSOT is Gree's house brand). 20 SEER2 / 8.6 HSPF2, rated heating operation to −13°F — not hyper-heat, and it doesn't need to be: the furnace holds the floor, this holds the room. R32, factory-precharged, 16-ft lineset in the box. 5-yr parts + compressor warranty whose bar is "per the manual and local codes," not "licensed installer" — TOSOT's own copy invites DIY.
| Tier | System | The trade | Price |
|---|---|---|---|
| Pick | TOSOT Cosmo 9k, 120V | See above — Gree-built, HA-native, R32, ~$595–700. | $595 |
| Field | Senville Leto 9k | Same money, proven SLWF-01 local-control dongle path — but the warranty explicitly requires a licensed installer. A DIY house buys that paper for nothing. | $700 |
| Field | Fujitsu Altair 300 9k | The name-brand floor — the only Mitsubishi-tier badge confirmed under $1.5k. Lower efficiency (17 SEER2) and cloud-app control; pedigree without the local-first soul. | $1,345 |
| Field | Mr Cool DIY 5th gen 9k | The quick-connect no-vacuum pitch, but the 4th gen is discontinued and the 5th gen runs $1,929–2,329 — a ~$1,400 premium to skip a vacuum pump, paid in cloud-only control. | $1,929+ |
| Field | Mitsubishi GS09 | The CN105-proven mod path — same money as the Mr Cool 5th gen, and it beats it. Real Mitsubishi engineering, but the local control is a solder job on the control board, not a supported path. | $1,923 |
Why 9k, not 6 or 12: the room math hasn't moved — 169 sqft with spillover duty, 6k leaves no margin, 12k short-cycles, a modulating 9k covers both the leaky era and the post-insulation one.
Why 120V
voltage ≠ efficiency
The voltage rationale has moved: 240V was only ever where Mitsubishi's hyper-heat catalog lived. Nothing about 120V costs this unit efficiency or capacity — SEER2/HSPF2 numbers above are for the 120V model as sold.
At 120V this unit wants a dedicated 20A circuit on 12 AWG (MCA 19A, MOP 20A; power lands at the condenser, the head feeds off the interconnect) — and in an outage it runs from any portable inverter generator's household outlet, no 240V inlet required (see Resilience).
The Install Runbook
flare-and-vacuum, not quick-connect — the honest shape
Standard flare-and-vacuum, not quick-connect — and that's fine. The lineset ships pre-flared with the charge waiting in the condenser, so the stock install is a short, ordered list, not a mystery:
- Lineset ships pre-flared, charge already waiting in the condenser — no brazing.
- Mount the plate into studs; drill the wall hole 2.2–2.8", sloped slightly downward so condensate runs outside, not into the stud bay.
- Hang the head, connect the pre-flared lineset — torque the flare nuts to the manual's table: 12–14 ft-lb on the ¼" liquid line, 23–29 ft-lb on the ⅜" gas line.
- Pull vacuum at the gas-valve service port. The manual's own bar is loose (−0.1 MPa for 10–15 min) — do it right anyway: micron gauge to 500 microns, and a cheap nitrogen pressure test first.
- Hold-test the vacuum before touching anything else.
- Open both valve cores with a hex key to release the factory charge into the lines.
- Bubble-test every joint.
- Drain the pump, wrap the lineset, commission the system.
Flaring only enters the job if a run gets shortened or a flare gets damaged. Max lineset run is 65 ft; there's no published charge-per-foot table, so the honest answer is stay near the 16 ft that ships in the box.
Tools & Materials
~$250 in tools, once — then it's yours for the next one
| Item | Why | Price |
|---|---|---|
| Vacuum pump + manifold gauge set | Pulls and holds the vacuum test that quick-connect kits skip | $90 |
| Micron gauge | The only accurate way to confirm 500 microns — the manifold's dial gauge isn't precise enough | $40 |
| Torque wrenches (¼" & ⅜") | Hits the manual's flare-nut spec (12–14 / 23–29 ft-lb) instead of guessing by feel | $45 |
| Flare kit | Insurance — only needed if a run gets shortened or a flare gets damaged | $35 |
| Nitrogen + regulator (or borrow) | The pressure test before vacuum — cheap, and worth doing anyway | $40 |
| Outdoor disconnect + whip + 12/2 wire | Not in the box — the dedicated 20A circuit's last few feet, at the panel run | ~$60 |
| Line-set cover kit | Hides the lineset run against the siding, keeps it out of weather | ~$40 |
Tools: ~$250 (reusable for the next job). All-in with the unit, the electrical bits, and the cover kit: ≈$945 — call it $850–900 if the nitrogen's borrowed and the lineset hides without a cover. Prices are street — check before buying.
Fine Print
the parts that aren't the pick, but matter
- R32, mildly flammable (A2L): no open flame near the work; the 9k unit's factory charge sits under every room-size threshold that would otherwise trigger extra ventilation rules.
- Freight, not the unit: the known weak spot is the pallet, not the hardware — photograph it on arrival and report any damage within 5 days.
- Register within 30 days for the extra 6 months of warranty coverage — a form, not a phone call.
- TOSOT Direct, the retailer: reviews of the storefront itself are mixed; the hardware underneath is Gree's, and that's fine. Judge the machine on its own.