140kwh weekly peak
20kwh daily
8h charge, 16h discharge
Water heating, cooking included (not realistic would use gas)
Solar panels 50% efficient in winter
20kwh / 8h charging = 2.5kw * 50% efficient = 5000w panels
13.6kwh discharge at night, / 16h = 0.85kw = 1200w inverter
1200w / 12v = 100a
100a * 16h = 1600ah batteries
24v or 48v likely
Inverter 2000 to 8000nzd
Solar 6sqm 60kg 1000nzd per kw
Solar 30sqm 300kg,5000nzd
Batteries 2 to 10 nzd per ah
Batteries 3200nzd to 16000nzd (lithium), likely 4800nzd
Cable, charge controllers, monitoring, etc 5000nzd

20k nzd worst case, likely less.

Advantages are no electricians fees, no permits, no down time, no bills, etc.

Feel free to nit pick and smash my assumptions.