Generators v UPS systems for long runtime periods

A generator provides backup power from by converting a fuel source, either diesel or liquid petroleum gas which is stored in a ‘day tank’ typically manufactured to provide 8 hours of runtime at full load. The tank can be refilled either from a remote storage fuel tank or fuel delivery vehicle. If sized properly, a generator could run for longer periods. UPS systems provide backup power from energy stored in their battery sets. The battery set is sized to provide a certain runtime period at a set load kVA or kW. Once depleted the battery set must be recharged. It is normally practice to size a UPS battery set for 10-30minutes where a standby power generator is in place or for longer periods up to several hours if there is no generator. The size and cost of the battery set in comparison to the a standby power generator can rise exponentially the longer the runtime required.