HVAC Capacitor Sizing & Replacement Guide
A failed capacitor is one of the most common reasons an air conditioner or heat pump won't start on a hot day. The good news: it's a cheap, fast part to replace once you know how to read it. This guide covers what run and start capacitors do, how to decode the label, how to pick an exact replacement, and the signs one is failing. Shop the full range in our HVAC capacitors collection.
Run vs. start capacitors
- Run capacitor — stays in the circuit the whole time the motor runs, giving the fan or compressor a steady phase shift for efficient operation. These are the round or oval cans you see on most condensers.
- Start capacitor — gives a brief, high-torque boost to get a motor spinning, then drops out. Usually a smaller black cylinder, often paired with a relay or a hard-start kit.
How to read the label
Two numbers matter:
- Capacitance (MFD or µF) — e.g. 45 MFD or a dual rating like 45+5 MFD. This must match your old capacitor exactly. A dual-run capacitor lists two values: the larger for the compressor (“HERM”) and the smaller for the fan (“FAN”).
- Voltage (VAC) — usually 370V or 440V. You can always replace a 370V with a 440V (higher voltage rating is fine); never go lower. Browse 370/440V run capacitors.
Single vs. dual-run capacitors
A single capacitor supports one motor — common for a standalone condenser fan (e.g. a 5 MFD or 10 MFD can). A dual-run capacitor combines fan and compressor support in one body, like a 30+5 MFD unit. Match the type your system originally used.
Round vs. oval
Shape is purely about fit — electrically they're identical. Round cans fit round brackets; oval cans fit tight cabinets. Match whatever your bracket holds, or use a universal strap.
Signs your capacitor is failing
- AC hums but the fan won't spin (you can sometimes start it with a stick — a classic weak-capacitor symptom)
- Bulging, domed, or leaking top on the capacitor
- Unit trips the breaker or shuts off on high heat
- Measured MFD reads well below the rated value on a multimeter
Choosing a replacement — checklist
- Match the MFD/µF rating exactly (both numbers on a dual capacitor).
- Match or exceed the voltage (370V → 370V or 440V).
- Pick the shape that fits your bracket (round or oval).
- For a compressor that struggles to start, add a hard-start kit for extra torque.
Ready to order?
Shop run capacitors, dual-run capacitors, and hard-start kits in the SPLYPRO capacitors collection. Orders over $50 ship free and most leave our warehouse in 1–2 business days. Not sure which one you need? Call 786-577-2500 or email csr@splypro.com — U.S.-based support, Monday–Friday.
| State | Resale Certificate | Charitable | Religious | Educational | Government | Farmer | Miscellaneous |
|---|---|---|---|---|---|---|---|
| Alabama | Multi‑Jurisdiction Form & Sales tax license | AL State‑Issued Certificate of Exemption | AL State‑Issued Certificate of Exemption | Multi‑Jurisdiction Form | Multi‑Jurisdiction Form | Multi‑Jurisdiction Form | Multi‑Jurisdiction Form & Sales tax license |
| Alaska | No Sales Tax State – No need to Apply | ||||||
| Arizona | AZ Form 5000A & Privilege Tax License | AZ Form 5000A & AZ State‑Issued Certificate | AZ Form 5000 & AZ State‑Issued Certificate | AZ Form 5000 & AZ State‑Issued Certificate | AZ Form 5000 & Tribal Card (if applicable) | AZ Form 5000 | AZ Form 5000A & Privilege Tax License |
| Arkansas | Streamlined / AR ST‑391 Form | AR State‑Issued Certificate of Exemption | TAXABLE – NOT ELIGIBLE | TAXABLE – NOT ELIGIBLE | Streamlined / AR ST‑391 Form | Streamlined / AR ST‑391 Form | Streamlined / AR ST‑391 Form & Sales & Use Tax Permit |
| California | Multi‑Jurisdiction / CA Resale Cert & Seller’s Permit | TAXABLE – NOT ELIGIBLE | TAXABLE – NOT ELIGIBLE | TAXABLE – NOT ELIGIBLE | Multi‑Jurisdiction Form & Fed Gov’t letter (Fed. Only) | Multi‑Jurisdiction Form | Multi‑Jurisdiction / CA Resale Cert & Seller’s Permit |
| Colorado | CO DR‑0563 MJ Form, State Sales Tax License & City License | CO DR‑0563 MJ Form, State Exemption Cert & City Exemption Cert | CO DR‑0563 MJ Form, State Exemption Cert & City Exemption Cert | CO DR‑0563 MJ Form, State Exemption Cert & City Exemption Cert | CO DR‑0563 MJ Form, State Exemption Cert & City Exemption Cert | CO DR‑0563 MJ Form, State Exemption Cert & City Exemption Cert | CO DR‑0563 MJ Form, State Sales Tax License & City License |
| Connecticut | Multi‑Jurisdiction / Resale Cert & Sales & Use Tax Permit | Cert 119 & 501(c)(3) letter | Cert 119 & 501(c)(3) letter | Public – Cert 134; Private – Cert 119 & 501(c)(3) letter | CT Cert 134 | State‑Issued Farmer Tax Exemption Permit | Multi‑Jurisdiction / Resale Cert & Sales & Use Tax Permit |
| Delaware | No Sales Tax State – No need to Apply | ||||||
| District of Columbia | Multi‑Jurisdiction Form & Sales Tax License | DC‑Issued Letter of Exemption | DC‑Issued Letter of Exemption | DC‑Issued Letter of Exemption | Multi‑Jurisdiction Form | TAXABLE – NOT ELIGIBLE | Multi‑Jurisdiction Form & Sales Tax License |
| Florida | State‑Issued DR‑13 Certificate | State‑Issued DR‑14 Certificate | State‑Issued DR‑14 Certificate | State‑Issued DR‑14 Certificate | State‑Issued DR‑14 Certificate | State‑Issued DR‑13 Certificate | State‑Issued DR‑13 Certificate |
| Georgia | Streamlined / GA ST‑5 & Sales Tax Certificate of Registration | GA‑State‑Issued Certificate of Exemption | TAXABLE – NOT ELIGIBLE | Streamlined or GA ST‑5 | Streamlined or GA ST‑5 | GA‑State‑Issued Gate Card | Streamlined / GA ST‑5 & Sales Tax Certificate of Registration |
| Hawaii | HI G‑17 Form & General Excise Tax License | HI‑State‑Issued Exemption Letter | HI‑State‑Issued Exemption Letter | TAXABLE – NOT ELIGIBLE | HI G‑17 Form (Federal Only) | HI G‑17 Form | HI G‑17 Form & General Excise Tax License |
| Idaho | ID ST‑101 or Multi‑Jurisdiction & Seller’s Permit | Idaho ST‑101 Form | TAXABLE – NOT ELIGIBLE | Idaho ST‑101 Form | Idaho ST‑101 Form | Idaho ST‑101 Form | ID ST‑101 or Multi‑Jurisdiction & Seller’s Permit |
| Illinois | Multi‑Jurisdiction / IL CRT‑61 & Certificate of Registration | IL‑State‑Issued Certificate of Exemption | IL‑State‑Issued Certificate of Exemption | IL‑State‑Issued Certificate of Exemption | IL‑State‑Issued Certificate of Exemption | Multi‑Jurisdiction Form | Multi‑Jurisdiction / IL CRT‑61 & Certificate of Registration |
| Indiana | IN ST‑105 or Streamlined & Registered Retail Merchant Certificate | IN ST‑105 or Streamlined | IN ST‑105 or Streamlined | IN ST‑105 or Streamlined | IN ST‑105 or Streamlined | IN ST‑105 or Streamlined | IN ST‑105 or Streamlined & Registered Retail Merchant Certificate |
| Iowa | IA Sales Tax Exempt Cert or Streamlined & Retail Sales Tax Permit | IA Sales Tax Exempt Cert or Streamlined (must be on IA Nonprofit list) | IA Sales Tax Exempt Cert or Streamlined | IA Sales Tax Exempt Cert or Streamlined | IA Sales Tax Exempt Cert or Streamlined | IA Sales Tax Exempt Cert or Streamlined | IA Sales Tax Exempt Cert or Streamlined & Retail Sales Tax Permit |
| Kansas | KS PR‑78 Form or Streamlined & Retailer’s Sales Tax Registration | KS PR‑78 Form or Streamlined | KS PR‑78 Form or Streamlined | KS PR‑78 Form or Streamlined | KS PR‑78 Form or Streamlined | KS PR‑78 Form or Streamlined | KS PR‑78 Form or Streamlined & Retailer’s Sales Tax Registration |
| Kentucky | KY 51A105 Form / Streamlined & Sales & Use Tax Permit | KY 51A126 Exemption Cert or Streamlined | KY 51A126 Exemption Cert or Streamlined | KY 51A126 Exemption Cert or Streamlined | KY 51A126 Exemption Cert or Streamlined | KY 51A126 Exemption Cert or Streamlined | KY 51A105 Form / Streamlined & Sales & Use Tax Permit |
| Louisiana | State‑Issued R‑1064 Form & Parish Certificate | LA‑State‑Issued Exemption Letter | TAXABLE – NOT ELIGIBLE | LA R‑1056 Form | LA R‑1056 Form or LA R‑1356 Form | LA R‑1007 Form | State‑Issued R‑1064 Form & Parish Certificate |
| Maine | Maine Resale Certificate | Maine State‑Issued Certificate of Exemption | Maine State‑Issued Certificate of Exemption | Maine State‑Issued Certificate of Exemption | Multi‑Jurisdiction Form (Fed. Only) & ME Exempt. Cert. | ME Exemption Card & ST‑L‑154 / ST‑L‑154A | Maine Resale Certificate |
| Maryland | Multi‑Jurisdiction Form & Sales & Use Tax License | Maryland State‑Issued Exemption Certificate | Maryland State‑Issued Exemption Certificate | Maryland State‑Issued Exemption Certificate | Maryland State‑Issued Exemption Certificate | Maryland State‑Issued Agriculture Exemption Certificate | Multi‑Jurisdiction Form & Sales & Use Tax License |
| Massachusetts | MA ST‑4 Form & Sales & Use Tax Registration | MA ST‑5 Form & State‑Issued ST‑2 Cert. | MA ST‑5 Form & State‑Issued ST‑2 Cert. | MA ST‑5 Form & State‑Issued ST‑2 Cert. | ST‑5 Form & State‑Issued ST‑2 Cert. | ST‑5 Form & State‑Issued ST‑2 Cert. | ST‑12 Form & State‑Issued ST‑2 Cert. |
| Michigan | Streamlined & Sales Tax License | Streamlined & 501(c)(3) letter or MI Exempt Cert | Streamlined & 501(c)(3) letter or MI Exempt Cert | Streamlined & 501(c)(3) letter or MI Exempt Cert | Streamlined & 501(c)(3) letter or MI Exempt Cert | Streamlined & 501(c)(3) letter or MI Exempt Cert | Streamlined & Sales Tax License |
| Minnesota | Streamlined & Sales & Use Tax Permit | Streamlined or MN ST‑3 Form | Streamlined or MN ST‑3 Form | Streamlined or MN ST‑3 Form | Streamlined or MN ST‑3 Form | Streamlined or MN ST‑3 Form | Streamlined & Sales & Use Tax Permit |
| Mississippi | MS Retailer’s Permit | MS‑State‑Issued Exemption Letter | TAXABLE – NOT ELIGIBLE | MS‑State‑Issued Exemption Letter | Multi‑Jurisdiction Form | Multi‑Jurisdiction Form | MS Retailer’s Permit |
| Missouri | Multi‑Jurisdiction / MO Form 149 & Sales tax license | MO‑State‑Issued Exemption Letter | MO‑State‑Issued Exemption Letter | MO‑State‑Issued Exemption Letter | MO Form 149 | MO Form 149 | Multi‑Jurisdiction / MO Form 149 & Sales tax license |
| Montana | No Sales Tax State – No need to Apply | ||||||
| Nebraska | Streamlined & Sales Tax Permit | Streamlined | Streamlined | Streamlined | Streamlined | Streamlined | Streamlined & Sales Tax Permit |
| Nevada | Streamlined & Sales Tax Permit | NV‑State‑Issued Exemption Letter | NV‑State‑Issued Exemption Letter | NV‑State‑Issued Exemption Letter | Streamlined | Streamlined | Streamlined & Sales Tax Permit |
| New Hampshire | No Sales Tax State – No need to Apply | ||||||
| New Jersey | Streamlined & Sales Tax Cert of Authority | State‑Issued ST‑5 Form | State‑Issued ST‑5 Form | Streamlined or Letter from School | Streamlined | Streamlined | Streamlined & Sales Tax Cert of Authority |
| New Mexico | State‑Issued Type 2‑NTTC Form | State‑Issued Type 9‑NTTC Form | State‑Issued Type 9‑NTTC Form | State‑Issued Type 9‑NTTC Form | State‑Issued Type 9‑NTTC Form | Statement of Affirmation from Farmer | State‑Issued Type 2‑NTTC Form |
| New York | NY ST‑120 Form & Sales Tax Cert of Authority | ST‑119.1 Form | ST‑119.1 Form | ST‑119.1 Form or NY AC‑946 Form | Letter from State of NY or NY AC‑946 Form | NY ST‑125 | NY ST‑120 Form & Sales Tax Cert of Authority |
| North Carolina | Streamlined / E‑595E Form & Certificate of Registration | TAXABLE – NOT ELIGIBLE | TAXABLE – NOT ELIGIBLE | TAXABLE – NOT ELIGIBLE | Streamlined / E‑595E Form | Streamlined / E‑595E Form | Streamlined / E‑595E Form & Certificate of Registration |
| North Dakota | Streamlined & Sales & Use Tax Permit | Streamlined | Streamlined | Streamlined | Streamlined | Streamlined | Streamlined & Sales & Use Tax Permit |
| Ohio | OH Blanket Form & Ohio Vendor License | OH Blanket Form | OH Blanket Form | OH Blanket Form | OH Blanket Form | OH Blanket Form | OH Blanket Form & Ohio Vendor License |
| Oklahoma | Streamlined & Sales Tax Permit | Streamlined & State‑Issued Exemption Cert | Streamlined & State‑Issued Exemption Cert | Streamlined & State‑Issued Exemption Cert | Streamlined | Streamlined Agriculture Card | Streamlined & Sales Tax Permit |
| Oregon | No Sales Tax State – No need to Apply | ||||||
| Pennsylvania | PA REV‑1220 Exemption Cert & Sales Tax License | PA REV‑1220 Exemption Cert | PA REV‑1220 Exemption Cert | PA REV‑1220 Exemption Cert | PA REV‑1220 Exemption Cert | PA REV‑1220 Exemption Cert | PA REV‑1220 Exemption Cert & Sales Tax License |
| Rhode Island | Streamlined / Resale Cert & Sales Tax License | Streamlined or State‑Issued Exemption Cert | Streamlined or State‑Issued Exemption Cert | Streamlined or State‑Issued Exemption Cert | Streamlined or State‑Issued Exemption Cert | Streamlined or State‑Issued Exemption Cert | Streamlined / Resale Cert & Sales Tax License |
| South Carolina | Multi‑Jurisdiction Form & SC Retail License | SC‑State‑Issued ST‑9 Certificate | SC‑State‑Issued ST‑9 Certificate | SC‑State‑Issued ST‑9 Certificate | Multi‑Jurisdiction Form | SC ST‑8F Form | Multi‑Jurisdiction Form & SC Retail License |
| South Dakota | Streamlined & Sales tax license | Streamlined & State‑Issued Exemption Cert | Streamlined & State‑Issued Exemption Cert | Streamlined & State‑Issued Exemption Cert | Streamlined | Streamlined | Streamlined & Sales tax license |
| Tennessee | Certificate of Resale or Streamlined | TN‑State‑Issued Certificate of Exemption | TN‑State‑Issued Certificate of Exemption | TN‑State‑Issued Certificate of Exemption or Streamlined | TN‑State‑Issued Certificate of Exemption or Streamlined | Certificate of Resale or Streamlined | Certificate of Resale or Streamlined |
| Texas | TX Resale Certificate & Sales & Use Tax Permit | TX Exemption Certificate & Comptroller Letter | TX Exemption Certificate & Comptroller Letter | TX Exemption Certificate & Comptroller Letter | TX Exemption Certificate | TX Agriculture Exemption Certificate | TX Resale Certificate & Sales & Use Tax Permit |
| Utah | Utah TC‑721 Form & Sales Tax License | Utah TC‑721 Form | Utah TC‑721 Form | Utah TC‑721 Form | Utah TC‑721 Form | Utah TC‑721 Form | Utah TC‑721 Form & Sales Tax License |
| Vermont | Streamlined & Sales Tax License | Streamlined | Streamlined | Streamlined | Streamlined | Streamlined | Streamlined & Sales Tax License |
| Virginia | VA ST‑10 Form & Certificate of Registration | VA State‑Issued Exemption Cert | VA ST‑13A Form | VA ST‑12 Form | VA ST‑12 Form | VA ST‑18 Form | VA ST‑11 Form |
| Washington | Reseller Permit | Reseller Permit | Reseller Permit | TAXABLE – NOT ELIGIBLE | Streamlined (Federal) | Reseller Permit or Farmer’s Cert | Reseller Permit |
| West Virginia | Streamlined & Business Registration Certificate | Streamlined | Streamlined | Streamlined | Streamlined | Streamlined | Streamlined & Business Registration Certificate |
| Wisconsin | Streamlined & Seller’s Certificate of Registration | Streamlined | Streamlined | Streamlined | Streamlined | Streamlined | Streamlined & Seller’s Certificate of Registration |
| Wyoming | Streamlined & Sales & Use Tax License | Streamlined | Streamlined | Streamlined | Streamlined | Streamlined | Streamlined & Sales & Use Tax License |