Adequate service for new water heater?

My water heater just went out. It was a 4500 watt/240 volt unit on 10 guage wire/30 amp circuit. I was looking at a 5500 watt 240 volt unit at lowes and was advised by their electrical department that I would have to have a 50 amp/6guage wire circuit to service it. (Lowes calculated by dividing 5500 watts by 120 volts, shouldn't it have been 240 volts). I looked at another 5500watt/240 volt heater at Sears in which the specification indicated that a 30 amp 10 gauge wire circuit was adequate. Could someone advise me on the code for a 5500 watt unit. Thanks

 

80% of the circuit would be 5760 watts, so the 10 guage 30 amp circuit should serve 5500 watts numerically. 240 volts by 30 amps = 7200 watts

 

It's just incredible how much misinformation you can get in the aisles of a home improvement center. As chfite said, a 5500 watt water heater will be fine on your existing wire and circuit.

 

I wonder if they stocked a 60 A single pole breaker?

 

I'll wager that they're not selling many 5500 watt heaters.