How do gas station pumps work without electricity?

As Hurricane Irma whips its way towards Florida, many residents are making both plans and back-up plans to brace for emergency.

In the event of a possible power outage, Floridians have been stocking up on flash lights, batteries, water, pet supplies, and food. Some are even rounding up lists of gas stations that pump gas without electricity, in case people need to leave the area during a blackout.

But exactly how do gas stations pump without electricity?

As it turns out, gas stations that pump while the power is out rely entirely on transfer switches and generators. In the past, gas stations weren’t required to have generators or an alternative way to power their gas pumping if the electricity went out—so during a blackout, residents would be left without power and gasoline.

After a string of hurricanes swept through the south of Florida in 2004 and 2005, lawmakers passed a bill requiring that any fill stations on evacuation routes install transfer switches, allowing them to switch over to generator power in the case of an emergency.

Oil companies with over 10 stations in one county—like Exxon Mobil and Shell—need to have portable generators available within 24 hours. Smaller gas station chains are exempt from that rule, but some still have transfer switches installed or generators on hand.

But How Do The Generators Run?

A portable generator relies on gasoline or diesel to run, whereas an automatic or standby generator, which is a permanent fixture in a building’s electrical system, relies on natural gas, propane or diesel to operate.

If you’re in an area where Hurricane Irma may touch down, you’ve probably already filled your tank in anticipation of the storm making landfall. Indeed, some gas stations in the Florida have already run out of gas, as many Floridians are attempting to leave town before the hurricane arrives over the weekend.

If you’re looking to buy gas before (or after) Irma hits, consider using Gas Buddy, an app that gives live updates about which gas stations do (and don’t) currently have gas.