Compressed-Air Leak Load and Annual Cost (Load/Unload Test)
Turns a stopwatch into a repair budget: with production off, the fraction of a cycle the compressor runs loaded (t_load / (t_load + t_unload), the DOE Compressed Air Challenge method) times the rated capacity is the leakage flow, converted to kilowatts at the system specific power (18-22 kW per 100 cfm) and to dollars at the run hours and rate. A neglected system loses 20-30 percent of its air to leaks, a well-run one under 10, and the difference is thousands a year on the plant's most expensive utility. Needs no flow meter. An estimate from a stopwatch test, not a metered audit.
Formula and source
leak_fraction = load_min / (load_min + unload_min); leak_cfm = compressor_cfm x leak_fraction; leak_kw = leak_cfm x specific_power / 100; annual_kwh = leak_kw x run_hours; annual_cost = annual_kwh x rate_kwh.
The US DOE Compressed Air Challenge load/unload leak test (leak fraction = t_load / (t_load + t_unload), leak flow = fraction x compressor cfm) and the compressed-air specific-power convention (18-22 kW per 100 cfm at 100 psig for a rotary-screw system), by name; the relations are public.
Audience
This tile is built for hvac and the adjacent professions in the HVAC group. The interactive calculator runs entirely in your browser. No account, no fee, no advertising, no tracking.
Related tools
Posture
Rough Logic answers the math question the working professional asks on the job. The site is a calm, fast, ad-free, account-free, ever-free reference. It does not interpret code. It does not replace the licensed professional. It does not store your inputs. The Authority Having Jurisdiction governs all installations and inspections.