Parallel type double-inner-container electric water heater and heating method thereof

The invention discloses a parallel type double-inner-container electric water heater. The parallel type double-inner-container electric water heater comprises a first hot water tank and a second hot water tank. The top of the first hot water tank communicates with the top of the second hot water tank through a communicating pipe, so that gas in the first hot water tank communicates with gas in the second hot water tank. A water inlet of the first hot water tank and a water inlet of the second hot water tank are connected with a cold water pipe through a first three-way valve. A water outlet of the first hot water tank and a water outlet of the second hot water tank are connected with a hot water outlet through a second three-way valve. The hot water outlet, the cold water pipe and a warm water outlet are connected through a water mixing valve. According to the parallel type double-inner-container electric water heater, gas in the first hot water tank communicates with gas in the second hot water tank through