In the modern world, we use electricity for so many things. We require electrical power to pump water into people's houses and to pump the sewage away. [You can imagine] what could happen if the sewage systems aren't pumping stuff away.
If you don't have power, you can't pump fuel into vehicles. If you don't have any fuel, traffic could come to a standstill.
Could the economy function?
Most of the time you're using credit cards, debit cards or you'll be getting money out of an ATM. If you've lost the power, the computers in the bank that keep track of our money will have back-up power, but not the ATMs or the machines in the shops. So if you had a big power outage, it wouldn't be long before we'd be trying to find cash.
What are the chances that something like this will happen soon?
A recent paper [published in February in the journal Space Weather] tried to estimate the chance of having a repeat of 1859 and came up with a value of a 12% chance of it happening in the next 10 years. That's quite a high risk.