A 24,000 BTU mini-split will not heat at the same rate as a 24,000 BTU gas heater.
A 24,000 BTU gas heater rated at 80% efficiency only delivers about 19,200 BTU/hr to the space
(24,000 × 0.80 = 19,200 BTU/hr). Higher-efficiency gas units deliver more, but nameplate BTU and delivered BTU are...