Quick Answer: If you’re searching “mini split capacitor” expecting a compressor part, you’re probably shopping for the wrong thing — nearly all modern mini splits use an inverter-driven DC compressor that doesn’t use a run capacitor at all, since the control board handles starting electronically instead. The part that actually fails is usually the outdoor condenser fan motor’s small run capacitor, typically 1-15 MFD at 450V — Supco’s mini-split-specific RC-series (RC1X450, RC8X450, RC15X450, roughly $2-$4 per our research) covers the common ratings. A generic central-AC-style dual-run capacitor (35-45+5 MFD, roughly $12-32) is sized for a different motor design entirely and isn’t the right match.
A central air conditioner’s outdoor unit has one easy-to-spot capacitor doing two jobs at once — starting the compressor and running the fan — which is why “AC capacitor” guides online default to a single 35-45+5 MFD dual-run part. A mini split usually isn’t built that way. The compressor is inverter-driven, so the control board — not a capacitor — handles starting it, per the same AC-induction-vs-brushless-DC distinction that explains why mini splits need an inverter in the first place. That leaves the outdoor fan motor as the part that’s actually still capacitor-dependent on most residential units, and only if it’s a PSC (permanent split capacitor) design rather than a newer ECM motor.
Mini-split-specific fan capacitors compared
| Product | MFD rating | Best for | Price |
|---|---|---|---|
| Supco RC8X450 | 8 MFD / 450V | Best overall — most common fan motor rating | ~$2-$4 |
| Supco RC15X450 | 15 MFD / 450V | Larger/high-BTU outdoor fan motors | ~$3-$5 |
| Supco RC1X450 | 1 MFD / 450V | Small single-zone fan motors | ~$1-$2 |
1. Supco RC8X450 — Best Overall
Supco RC8X450 Mini-Split Run Capacitor (8 MFD, 450V)
- 8 MFD at 450V is the rating that shows up most often across residential mini split outdoor fan motors in this size range, per retailer cross-listings — the one worth checking first against your old part's printed rating.
- Plastic case with quad blade quick-connect terminals built to IEC 252 standard and UL recognized — a drop-in match for the connector style most mini split fan motor harnesses already use, not a central-AC-style capacitor repurposed for the job.
- Small enough to fit mini split outdoor unit electrical compartments that a bulkier central-AC dual-run capacitor physically won't clear.
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2. Supco RC15X450 — Best for Larger Fan Motors
Supco RC15X450 Mini-Split Run Capacitor (15 MFD, 450V)
- Higher 15 MFD rating matches the larger outdoor fan motors found on bigger single-zone condensers and multi-zone outdoor units, where the 8 MFD rating above isn't enough capacitance to keep the motor running efficiently.
- Same mini-split-specific form factor and terminal style as the RC8X450 — the rating is the only real difference, which is why matching the printed MFD number on the old part matters more than guessing by BTU size alone.
3. Supco RC1X450 — Best for Small Single-Zone Units
Supco RC1X450 Mini-Split Run Capacitor (1 MFD, 450V)
- The lowest common MFD rating in the mini-split-specific range, sized for the smaller fan motors on compact single-zone condensers rather than the higher-draw motors on larger or multi-zone outdoor units.
- Cheapest of the three — a reminder, alongside the others, that the capacitor itself is rarely the expensive part of a "capacitor repair" quote.
The product you’ll find first — and why it’s usually wrong
Search “AC capacitor” and the top results are almost always a dual-run capacitor like a Titan Pro 45+5 MFD at 370-440V, priced around $12-32 — built to run a central AC’s single-phase compressor and fan off one part with two separate capacitance ratings. That part doesn’t fit a mini split’s compressor because there’s nothing on an inverter-driven compressor for it to connect to. Buying one for a mini split fan motor also typically means the wrong case size and the wrong terminal count for the connector already on the harness. The three-digit price tag on some of these dual-run parts is also doing a lot of the work convincing buyers they’ve found the “real” capacitor — the correct mini-split-specific part is usually a one- or two-dollar component, which is exactly why our repair cost breakdown prices a full capacitor replacement, part and labor, at $105-200: almost all of that is diagnostic time and the licensed labor to safely discharge and access the electrical compartment, not the capacitor itself.
The bottom line
Before buying anything, confirm which part actually failed — if the outdoor unit hums but the fan won’t spin while everything else runs normally, that’s the classic fan-capacitor symptom our mini split not cooling guide already covers, and the part you need is almost certainly a small mini-split-specific capacitor like the Supco RC8X450 (8 MFD/450V covers most units), stepping up to the RC15X450 for larger fan motors or down to the RC1X450 for compact single-zone condensers. Match the MFD and voltage printed on the old part exactly — don’t guess by BTU size, and don’t reach for a generic central-AC dual-run capacitor, which is sized for a different motor design and often won’t physically fit. Replacement itself is still licensed-technician work due to the stored electrical charge, the same line our repair cost guide and troubleshooting hub already draw — these products are worth knowing by name so you can confirm the quote, not to install one yourself.