Best answer by Eva_Boost
With PAYG+ you don't get a monetary amount of emergency credit, you get a 24-hour ‘non-disconnect’ period. That means you’ll still get gas and electricity for the next 24 hours without needing to top up. You'll pay for the energy you've used during this period when you top up next.
If your meter runs out of credit during weekends, bank holidays and evenings you won't go off supply, you'll get a longer non disconnect period.
The only way to avoid this is to top up enough to stop your balance dropping below £0.