So we can double per population to 10 million, and all of us have an EV (adults) and the consent list is enough? Great news. These extra houses dont use power? Nor the businesses that must employ them? And 30 years to replace our fleet? That in itself is a fail. 30 years. All of us, not the double own one or two cars, and it will take 30 years? That means that the subsidy proposed is not actually relevant? Obviously it isn't, when you account for production, supply and current pricing, i.e. real value + R+D
At our present rate of growth (2.1%) it will take around 35 years to double our population to 10 million people, which fits in quite nicely with a 30 year time frame to replace all our vehicles. I am confident that the people in charge of New Zealand's electrical generation and transmission systems can handle that.
In practice I expect the fleet replacement to be quicker than that because all indications are that EVs will be outright cheaper than ICEs within 5 years even with pessimistic forecasts on battery cost reduction. At that point you'll have no more reason to buy an ICE than you will a steam engine. But again: the people that run the power grid can see all this coming just as well as anyone else, if not better. The EV fleet is not armageddon for the electric power industry. It's payday.