I'm still thinking about heating water with 1/3 the usual energy using a Haier
5K Btu/h window AC ($84 at Wal-Mart.) The pipes connect to the condenser coil at the top, so we could build a thin aquarium around it with no replumbing or recharging and pump 1.5 gpm of 110 F water out through a $168 Doucette SB1-20
400 Btu/h-F plate heat exchanger with a 110 F thermostat and pump 60 F cold water into the other side of the heat exchanger from a cold kitchen tap and back into the hot tap, and dump some hot water from the hot tap into the sink with a solenoid valve if the cold tap ever reaches say, 100 F, when/if the tank water heater completely fills. Heating 50 gallons of 60 F water to 110 takes about 21K Btu, and the AC would make about 5000(1+1/3) = 6700 Btu/h, so we might fill the tank in 3 hours, with no hot water use.
When I blocked the Haier AC condenser airflow to make the exit temp 110 F, its cool air temp and power use (from a Kill-a-Watt) barely changed.
This could be more efficient than a typical "portable air conditioner" with air hoses. Removing the condenser fan blade might also raise the COP.
Nick