From Juan Cole’s Informed Comment site:Israel Bombs Gaza back to Stone Age: Razes only Power Plant & Plunges Strip into Darkness

Israel launched a 7-hour campaign of intensive bombing of Gaza on Tuesday, destroying its only power plant. Gaza can no longer generate its own electricity. Without electricity, the water purification plants cannot operate and the drinking water ends up being mixed with sewage or salt water. Without electricity, patients on life support in the hospitals just die, even if Israel does not bomb the hospital, as it has in some instances. The power plant will take the good part of a year to rebuild even after the war ends. Gaza gets some electricity from Israel and Egypt, but many of those lines have been damaged in the fighting.

Subsequent Googling indicates that the Gaza strip may have lost up to 80% of its electric power. This seems to me to be collective punishment.