Gas Hot Water Heater

It has 2 D-cell ( or was it a smaller type ? ) inside . There is no electric wire going inside or out . When the water heater notices flow , it automatic fires up , using it's batteries inside , and switches of automatic also . There is no small flame when it is not in use .
They recommend changing the batteries once a year .
With me i put the heater in the kitchen , as i have my gasbottle/line splitter to my cooker and 1 to my water heater . Works like a breeze , no matter what the outside temp ( water temp ) is as you have plenty of reserve ( max power is about 10kw for this model ) .
I am sure if i would have bought a electric model i ended up with something more expensive , even if the unit costs the same ... because no need for big expensive wires .