Power drills come in 3 sizes; 1/4, 3/8, and 1/2-in. Size refers to the largest capacity of bit that will fit in the drill's chuck. 3/8-in. drills are the most versatile. They're powerful, yet light enough to easily hold and manage. Larger bits can drill bigger holes, so 1/2-in. drills are best for big, heavy-duty projects. Drills with higher RPM ratings (1200-rpm or more) are better for boring smaller holes into wood. Lower speed models are better at making larger holes into metal.
Look for the EnergyGuide label that tells how much energy the water heater uses in one year. Also, look for the FHR (First Hour Rating) of the water heater, which measures the maximum hot water the heater will deliver in the first hour of use. If you typically need a lot of hot water at once, the FHR will be important to you.