This is how much cash should you stash in your earthquake emergency kit

Estimate how much cash your family will need for three days in an emergency.

When preparing for the Big One, most people think of stashing away essentials like food, water and batteries. But there's another item that's just as essential: cash.

That's because a large earthquake has the potential to knock out parts of the power grid for long enough periods of time that ATMs may not work and credit cards and smartphone payment systems could be offline, experts said.

The Federal Emergency Management Agency advises people to always have enough cash on hand in a safe place in their home to cover a family's basic needs for a few days — including food, fuel and other day-to-day essentials.

"Having cash on hand is always a good idea," said Jose Lara, seismic hazards branch chief with the Governor's Office of Emergency Services. He said that with inflation taking a bite out of many Californian's budgets these days, stockpiling emergency funds is harder, but setting aside a few dollars in small bills each week or month for an emergency could make all the difference.

"We always encourage people to save what they feel comfortable with that aligns with their budget," with the aim of being able to be self-sustaining for three to seven days, Lara said.

"After an earthquake, depending on the size, we may be in a situation where, for a few days, people have to fend for themselves," he said.

Lara pointed to California's earthquake warning site, the Earthquake Country Alliance and Listos California for disaster preparedness checklists and further reading.

Besides just stashing cash, it's a good idea to have traveler's checks in a safe place at home, along with a disaster preparedness kit, according to the Red Cross Disasters and Financial Planning Guide.

"To determine how much money to set aside, estimate how much your family would need for at least three days," the guide recommends. Beyond getting through the initial phases of a disaster like an earthquake, stashing enough money in a separate account for emergencies to cover bills for three to six months is also a good idea.

"Consider depositing some funds in a financial institution that is outside of your local area to decrease the chances of it being affected by the same disaster," the Red Cross guide says.

FEMA also recommends knowing your FICO credit score, which lenders use to decide whether to extend a line of credit, in case you need to borrow money.

Lara of the state agency said having critical financial documents in a safe place is also essential. Having originals and copies of hard-to-replace documents like deeds to a home, passports and especially insurance papers is critical when internet and cell phone service may not be working.

Chase DiFeliciantonio is a San Francisco Chronicle staff writer. Email: [email protected] Twitter: @ChaseDiFelice