The electricity has gone off.
SAL-ta-ta — three syllables, stress on the first.
Report to the host immediately if the electricity goes off. It is often just a tripped circuit breaker.
'Saltare la luce' (literally 'the light jumped') is a typical Italian colloquial expression for when electricity trips out. The 'quadro elettrico' (electrical panel/fuse box) has a 'salvavita' (residual current device) that trips when overloaded.
Dov'è il quadro elettrico?
Where is the electrical panel?
Ask to find it so you can reset the breaker yourself
Sono saltate le luci in tutto l'appartamento.
The lights have gone out in the entire apartment.
Describe the extent of the outage
Come si resetta il salvavita?
How do I reset the circuit breaker?
Ask for instructions to reset the breaker — it is usually a simple switch flip
Italian apartment electrical systems are often older and can trip when too many appliances run simultaneously — hairdryer + kettle + air conditioning is a classic combination that causes a trip. The 'salvavita' (safety switch) is usually easy to reset and found in the 'quadro elettrico' in the entrance hallway.