When compared to gas type tankless water heaters, Stiebel Eltron Tempra 20 Plus cost less and is less expensive to install, since it does not require venting parts. While gas type tankless water heaters with outside venting may have a 5-20% efficiency reduction (due to heat loss from gases escaping through the vent), Stiebel Eltron Tempra 20 Plus is designed to be virtually 100% efficient. Multiple heating elements inside the Tempra 20 Plus models activate as the water demand increases, thus providing maximum efficiency and complete comfort. The Advanced Flow Control system, available in Plus models only, monitors and adjusts the water flow to assure a constant temperature output. Specs: Flow Rate: 0.58 - 4.5 GPM; Maximum Operating Pressure: 150 PSI; Hot / Cold inlet connections: 3/4" male threaded (Male NPT); Dimensions (Width x Height x Depth): 16 5/8" x 14 1/2" x 4 5/8"; Weight: 15.4 lbs; Voltage: 208V/240V; Amperage: 70 Amps at 208V / 80 Amps at 240V; Phase: 2 x single; Wattage: 14.4 kW at 208V / 19.2 kW at 240V; Min. Circuit Breaker Size Required: 2 x 50 Amps; Recommended Wire Size: 2 x 8 AWG copper;