New cylinder - 1.5k NZD + half day of labour (so another $500). My current one stores about 6-8 kWh.
15kWh battery - 5.5k NZD + and hour of DIY.
So technically battery is more expensive but more useful.
Also easiest with water heater would be cranking up the temperature, but I really hate dealing with scolding water coming from taps (especially with small kids around).
Another thing with battery I can charge with whatever solar excess I have, but with hot water my only option is 16A.
>Also easiest with water heater would be cranking up the temperature, but I really hate dealing with scolding water coming from taps (especially with small kids around).
Your water heater temperature isn't exactly my business but please look into sanitary norms on minimum safe temperature. Water heaters have standing water and bacteria might start living there if the temperature isn't sufficient. I think legionnaires' disease is one of the most prevalent dangers.
FWIW you can get thermostatic mixing valves that limits the maximum temperature of the water by mixing in cold water. Lets you run the tank hotter but have the same outlet temp. Fairly cheap I believe.
At this point getting some batteries would likely be cheaper than new boiler + plumber to install it.