You can never have enough...

[harm_less]

After my hot water cylinder failed for a second time due to the chlorine in the water I have gone for an infinity gas system, so far I’m still on my first tank of gas after 15 months so cost of hot water is $9 a month and going down. It will pay off the cost of the system in a couple of years at this rate. 

I'm curious about who told you that HWC failure was due to chlorine. Normally water pH is the culprit such as from unbuffered rainwater in a roof water supply which probably isn't the case for you unless you're chlorinating your water tank/s.

I know the sulphate levels in places like Rotorua can present corrosion issues so maybe worth getting your water supply tested so that the Infinity unit doesn't fail prematurely.