Storage tank water heaters (40–80 gallon) are the most common type. They maintain a reservoir of hot water at all times. Gas units recover quickly; electric units are slower. They're the lowest upfront cost but continuously lose heat through the tank walls (standby loss).
Tankless (on-demand) water heaters heat water only when needed, eliminating standby loss. They provide unlimited hot water but have a maximum flow rate — a single unit may struggle to supply two simultaneous showers. Gas tankless units have higher flow rates than electric.
Heat pump water heaters (HPWHs) use the same refrigeration cycle as a heat pump to move heat from the surrounding air into the water. They're 2–3× more efficient than electric resistance units. They work best in unconditioned spaces (basements, garages) where they can draw heat from the ambient air.
For most PA homes with a gas supply, a gas tank or tankless unit is the practical choice. For all-electric homes or those with a large basement, a heat pump water heater offers significant energy savings. DMES LLC can help you choose based on your home's setup.
Information provided is general guidance for homeowners. Every home is different — contact DMES LLC for advice specific to your situation.