Why lighting is a habitability basic
Yes. A home with no working lights can be a habitability issue in California, because state law requires rentals to have safe, working electrical lighting.
Civil Code Section 1941.1 lists electrical lighting as one of the basics a landlord must maintain in good working order. A home with no light in living areas, hallways, or stairways is not just inconvenient — dark stairs and rooms can lead to falls and other injuries, which raises the safety stakes.
If the problem is a light fixture the landlord installed, or the wiring behind it, fixing it is generally the landlord's responsibility. If it is simply a burned-out bulb in a fixture you control, that is usually a quick fix on your end.
Report the problem in writing and describe which areas have no light, paying special attention to stairways and exits. If your landlord will not restore lighting the law requires them to provide, a free, confidential review can explain your options.
This is general information about California tenant rights, not legal advice. Every situation is different.