Why do my refrigerant top-up records look low after I installed many new units?
A top-up record shows a leak only when a technician refills the unit. The Intergovernmental Panel on Climate Change (IPCC) warns that mass balance can underestimate emissions when equipment stocks are growing, because a lag separates the leak from the service that detects it.
What the IPCC says
The Guidelines list as a drawback of the mass-balance approach that it "can underestimate emissions when equipment stocks are growing, because there is a lag between the time the emissions occur and the time they are detected (through equipment servicing)". They add that the underestimate is relatively large where hydrofluorocarbons (HFCs) have been used for less than ten years, "because much of the equipment will have leaked without ever being serviced", and gets smaller the longer HFCs are used. The statement is about a country. Applying it to a site that has just added many units is our reading.
What it looks like in your records (our reading for a site)
- Our reading for a site: new units are rarely topped up in their first years, so those years show little or no gas bought.
- Our reading for a site: the first service refills the accumulated loss in one go, so one year looks heavy.
- The Guidelines note that servicing is done every year, every three years or sometimes not at all, as in domestic refrigeration. A year with no top-up is not proof of no leak. These points apply the lag warning, which the Guidelines write for a country, to one site.
What to do
- Keep reporting actual top-ups. The Guidelines ask for the same method and data sources every year.
- List units not yet serviced, with nameplate charge and install date.
- Work out the Table 7.9 screening range for them and note it beside the figure as a cross-check, not an addition to the total.
- When the first service happens, label the top-up as covering more than one year.
20 split air conditioners installed in early 2024, first serviced in January 2026
- Gas in the units: 20 x 1.5 = 30 kilograms of R-32
- Table 7.9 operating leak for residential and commercial air conditioning: 1% to 10%, so 0.3 to 3.0 kilograms a year
- Over 2 years: 0.6 to 6.0 kilograms, recorded as zero in 2024 and 2025 and as one top-up in 2026
- With the IPCC Sixth Assessment Report (AR6) value for R-32 of 771: 0.6 x 771 = 462.6 kilograms to 6.0 x 771 = 4,626 kilograms of carbon dioxide equivalent (CO2e) landing in the 2026 figure
Units, charge and dates are examples. Table 7.9 is a 2006 national default.
What Senseible does here
Senseible reads fuel invoices and electricity bills into dated records. It does not read recovery notes, service tickets or equipment nameplates, so keep those papers yourself and add the kilograms to your Scope 1 figure.
Sources: IPCC 2006 Guidelines, Volume 3, Chapter 7: Emissions of Fluorinated Substitutes for Ozone Depleting Substances, IPCC Sixth Assessment Report, Working Group I, Chapter 7 Supplementary Material, Table 7.SM.7
Last reviewed 2026-11-05. The lag warning is written for national inventories. Its use for one site is our reading.