EPA Subpart C Leak Rate Calculation Guide (2026 Rules)

What Changed in 2026?

The EPA's new Subpart C regulations under the American Innovation and Manufacturing (AIM) Act significantly expanded refrigerant management requirements. The most dramatic changes are lower thresholds and stricter leak rates for HFC-containing systems.

Key Changes from Old Rules

❌ OLD (Section 608)

• 50 lb threshold
• 35% leak rate (commercial/industrial)
• Only ODSs (R-22, etc.)
• Effective since 1990s

✅ NEW (Subpart C)

• 15 lb threshold (GWP >53)
• 20%/30%/10% leak rates
• HFCs (R-134a, R-404A, R-410A)
• Effective January 1, 2026

New Leak Rate Thresholds (Effective Jan 1, 2026)

40 CFR § 84.106 Leak Rate Thresholds

Commercial refrigeration:20%(≥15 lbs, GWP >53)
Industrial process refrigeration:30%(≥15 lbs, GWP >53)
Comfort cooling:10%(≥15 lbs, GWP >53)
Refrigerated transport:10%(≥15 lbs, GWP >53)
Other appliances:10%(≥15 lbs, GWP >53)

Important: The 15 lb threshold applies to refrigerants with a Global Warming Potential (GWP) greater than 53. This includes R-134a (GWP 1,430), R-404A (GWP 3,922), R-410A (GWP 2,088), and most other HFCs.

When Must You Calculate Leak Rate?

Under § 84.106(b), you must calculate the leak rate every time refrigerant is addedto an appliance, with only three exceptions:

Exceptions (No leak rate calculation required):

✓ Immediately following a retrofit of the system
✓ Installation of a new refrigerant-containing appliance
✓ Additions that qualify as seasonal variance adjustments

Two Calculation Methods

Subpart C allows two different methods for calculating leak rates. You can choose which method to use, but must be consistent in your approach.

Method 1: Annualized Leak Rate

Leak Rate = (Total Refrigerant Added in 12 Months ÷ Full Charge) × 100

Sum all refrigerant additions over the past 12 months

Method 2: Rolling Average Leak Rate

Leak Rate = (Refrigerant Added ÷ Full Charge) × 100 × (365 ÷ Days Since Last Addition)

Annualize based on days since the last refrigerant addition

Step-by-Step Calculation Process

1. Verify equipment is covered: Must have ≥15 lbs refrigerant with GWP >53
2. Identify equipment type: Commercial refrigeration, industrial process, comfort cooling, etc.
3. Determine full charge: Check equipment nameplate or manufacturer specifications
4. Track refrigerant additions: Record date and amount every time refrigerant is added
5. Choose calculation method: Annualized or rolling average
6. Calculate leak rate: Use appropriate formula
7. Compare to threshold: Check against equipment type's threshold (10%, 20%, or 30%)
8. Document everything: Maintain records for 3 years after equipment retirement

Practical Example

Scenario: Supermarket refrigeration system (commercial refrigeration)

• Full charge: 300 lbs R-404A (GWP 3,922)
• Equipment type: Commercial refrigeration
• Threshold: 20%

Service History (12 months):

• January 2026: Added 20 lbs
• April 2026: Added 15 lbs
• August 2026: Added 25 lbs
• Total added: 60 lbs

Annualized Calculation:

Leak Rate = (60 ÷ 300) × 100 = 20.0%

Result: AT THRESHOLD - If leak rate exceeds 20%, repair required within 30 days and follow-up inspections must be conducted until leak rate drops below threshold.

What Happens If You Exceed the Threshold?

When your leak rate exceeds the applicable threshold, you must take immediate action under § 84.106:

Required Actions:

1. Repair deadline:
- • 30 days for most appliances
- • 120 days if industrial process shutdown required
2. Verification testing:
- • Initial verification within 30/120 days after repairs
- • Follow-up verification within 10 days of initial test
3. Follow-up inspections until fixed:
- • Quarterly for systems with 500+ lbs refrigerant
- • Annually for systems with 15-500 lbs refrigerant
4. Alternative option: Retrofit or retire the equipment instead of repairing

Annual EPA Reporting Required

If your leak rate exceeds 125% of full charge capacity in a year, you must report to the EPA by March 1 annually.

Common Calculation Mistakes to Avoid

❌ Using incorrect full charge capacity from outdated nameplates
❌ Not accounting for refrigerant recovered before repairs
❌ Mixing annualized and rolling average calculation methods
❌ Forgetting to exclude retrofits, new installs, and seasonal variances
❌ Using old Section 608 thresholds (35%/10%) instead of new Subpart C thresholds (20%/30%/10%)
❌ Not calculating leak rate every time refrigerant is added
❌ Failing to update calculations after equipment modifications
❌ Not maintaining proper documentation for 3 years

Required Documentation & Recordkeeping

Under § 84.106(l), owners and operators must maintain comprehensive records for 3 years after the appliance is retired:

Required Records:

✓ Equipment information (model, serial number, location)
✓ Date of installation and full charge capacity
✓ Date and amount of every refrigerant addition
✓ Leak rate calculations and methodology used
✓ Repair records (dates, actions taken, verification tests)
✓ Follow-up inspection records
✓ Extensions requested and granted
✓ Equipment retirement or retrofit documentation
✓ Annual EPA reports (if leak rate exceeds 125%)

Equipment Exemptions

Not all equipment is subject to Subpart C leak repair requirements:

NOT Subject to Subpart C:

🚫 Appliances with <15 lbs of refrigerant
🚫 Refrigerants with GWP ≤53 (R-744/CO₂, R-717/ammonia, hydrocarbons)
🚫 Appliances containing only ozone-depleting substances (covered under Section 608)
🚫 Residential and light commercial AC/heat pump systems (covered under Subpart B only)

Why Automated Tracking is Essential

With the new 15 lb threshold, thousands of previously unregulated systems now require leak rate calculations every time refrigerant is added. Manual tracking of these calculations across multiple locations and equipment types is:

• Time-consuming and prone to human error
• Difficult to maintain consistent calculation methods
• Challenging to track follow-up inspection schedules
• Hard to ensure 3-year recordkeeping compliance
• Nearly impossible to manage March 1 EPA reporting deadlines

Automated compliance software eliminates these risks by calculating leak rates instantly upon refrigerant addition, automatically applying the correct threshold for each equipment type, scheduling required inspections, and generating audit-ready reports.