LeakLedgerPart 84 guide
Annualizing vs Rolling Average: How to Calculate Leak Rate Under §84.102
40 CFR 84.102 gives two ways to calculate a refrigerant leak rate: the annualizing method and the rolling average method. They can give very different answers for the same appliance, and the rule says one method must be used for all covered appliances at an operating facility. Here are both, worked through on the same service history.
The annualizing method
Step 1: pounds added to return the appliance to full charge (one addition, or several related to the same leak) ÷ full charge. Step 2: the shorter of the days since the last addition or 365, ÷ 365. Divide step 1 by step 2 and multiply by 100 (§84.102, "Leak rate" (1)).
It projects a single leak event forward to a year. A small top-off shortly after the previous one produces a high rate.
The rolling average method
Sum the pounds added over the previous 365 days — or since the last successful follow-up verification test showing all identified leaks repaired, if that's less than a year — and divide by the full charge, times 100 (§84.102, "Leak rate" (2)).
It reflects what the appliance has actually lost over the last year.
Same appliance, two answers
A walk-in freezer with a 40 lb full charge (commercial refrigeration, 20% threshold). Additions in 2026: 6 lb on March 1 and 3 lb on April 1.
| Addition | Annualizing | Rolling average |
|---|---|---|
| Mar 1: 6 lb (first in 2026) | 6 ÷ 40 = 15.0%, × 365 ÷ 365 = 15.0% | 6 lb since Jan 1, 2026 ÷ 40 = 15.0% |
| Apr 1: 3 lb (31 days later) | 3 ÷ 40 = 7.5%, × 365 ÷ 31 = 88.3% — exceeds | (6 + 3) ÷ 40 = 22.5% — exceeds |
Both exceed 20% on April 1 here, but by very different margins. Change the second addition to 2 lb: annualizing gives 2 ÷ 40 × 365 ÷ 31 = 58.9% (exceeds), while rolling gives 8 ÷ 40 = 20.0% — not over the threshold, because the rule triggers only above it. The method can decide whether a repair clock starts.
The first calculation in 2026
For the first calculation after January 1, 2026, the annualizing method substitutes 365 days for the days since the last addition, and the rolling method uses the pounds added since January 1, 2026 (§84.106(b)(1)–(2)). That's why the March 1 rows above give the same 15.0%.
Choosing and switching
- One method for every covered appliance at an operating facility (§84.102).
- Switching is allowed only when an owner acquires a facility that used a different method, the affected appliances aren't over the threshold under either method, and the change is recorded (§84.106(b)(3), (l)(3)).
- The method is the owner's choice; contractors should know which one each customer uses before reporting a rate.
Common mistakes
- A wrong full charge. Every rate divides by it. Use one of the four §84.102 methods and record which.
- Leaving out additions by another contractor. The rate is only as complete as the records.
- Ignoring the follow-up test date in the rolling window — it can shorten the lookback.
- Counting exempt additions: no calculation is needed for an addition right after a retrofit or new installation, or for a seasonal variance (§84.106(b)).
Run both methods on your own numbers in the leak rate calculator.
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This guide summarizes 40 CFR 84.102, 84.106 and 84.108 as published in the eCFR. It is not legal advice; where the rule is unclear we say so. Read the rule: 40 CFR Part 84, Subpart C.