GWP is the number that compares a gas’s greenhouse effect with CO₂. A 1 kg leak of R404A, with a GWP of 3,922, has the same effect as emitting 3,922 kg of CO₂. If a cold room system contains 20 kg of R404A, its "CO₂-equivalent charge" is 78 tonnes CO₂e; in the F-gas regulation, leak check frequency and bans are determined by exactly this value (thresholds of 5, 50 and 500 tonnes CO₂e).
GWP values of refrigerants (IPCC AR4, as used in F-gas legislation): R404A 3,922 · R507A 3,985 · R410A 2,088 · R134a 1,430 · R449A 1,397 · R448A 1,387 · R407C 1,774 · R32 675 · R513A 631 · R454C 148 · R1234yf 4 · R290 3 · R744 1 · R717 0. Regulations classify by these values: above 2,500 banned, below 150 "low GWP".
GWP describes only the damage a refrigerant does when it leaks; the real climate impact of a system is usually the electricity it consumes (indirect emissions). So a low-GWP but inefficient system can be more harmful than a well-maintained, efficient one. Our refrigerant chart lists the GWP and safety class of every refrigerant.