Dual water heaters

[David Lyons]

32962
I found this water heater arrangement on a recent inspection. The output on the electric heater (on the left) feeds into the gas heater (on the right).
I've not seen this arrangement before and can not figure out why this would have been done. Both units are active and producing hot water.
Has anyone seen this before? and if so, why was this done? (the water softener in the foreground is not connected.)

[Jim Port]

It may have been done strictly for storage capacity and to be able to fill large soaking tubs. Depending on operating cost of electric vs gas it may make sense. The gas might afford quicker recovery.

[Dom D'Agostino]

There is a recirculating pump in the photo, perhaps they needed extra hot water for remote devices or fixtures.

Dom.

[Jerry Peck]

I also provides hot water when the power goes out (because of the gas water heater).

There are some questionable items shown too.

[Marshall Brown]

It is possible the home is served by an "Off-Peak" service and that might make the electric water heater the less expensive to operate under typical conditions but allow continued service when the power is off.