Why NFPA 20 sometimes forces the noisier, harder-to-maintain diesel engine on a design instead of the simple, quiet electric motor — and it isn't about which one is cheaper to run.
On paper, an electric motor looks like the obvious choice to drive a fire pump: it's quieter, smaller, needs less routine attention, and has no fuel to store or spill. A diesel engine driver is the opposite on every one of those counts — it needs a fuel tank, starting batteries, a cooling system, an exhaust discharge path, and a weekly test run just to stay ready. So why does NFPA 20 so often specify diesel anyway? Because neither standard is actually optimizing for "simplest to own." They're optimizing for one question: will this pump still run if the very fire it's responding to has also taken out the building's normal power? An electric motor can only answer "yes" to that question if it's fed from a power source NFPA 20 recognizes as reliable under fire conditions — not just from ordinary utility service.