Install a timer or wi-fi control that enables you to time when you heat your water. If you have solar panels, the best time to heat your water is during the day when solar production is at its peak and when the heat pump works most efficiently.

About 10 - 12 years. 

Yes. While heat pumps work more efficiently in warmer climates, they do still work effectively in cold climates. The better quality heat pumps work very efficiently in both cold and warm climates and heat pumps heat roughly half the homes in Norway, Finland, and Sweden, which get a lot colder than New Zealand. Our advice is to not go with one of the cheaper versions.

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If you are able to power your electric resistive water heater from a large solar array during the day, it may make economic sense for you to keep it. It will still use 3 to 4 times more energy than a heat pump (which is why we recommend heat pumps) but if your budget is restricted (as the upfront cost of a heat pump is more expensive) it may be worth adding a timer to your heater and drawing on solar. Over 15 years, electric resistive with solar and the grid is around the same cost to run as a hot water heat pump on the grid including the upfront costs.  

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