Water heaters for TS4 as...

Electric or gas water heaters, which gas heaters don't need electric consumption, however Sims will need to separately pay for gas each week.

Electric heaters, which make them no need to pay but do add to the Sim's Bills.

They will give positive moodlets each time the Sim uses anything water-related indoors.

If it is removed then readded then it will simply add to the cycle again.