30-50% over 500k build is 10x more than 10k solar or 5k worth of batteries.

I've just setup electrical heating for my bedroom (HA PID sensor). Uses about 450KWh - $90 NZD worth of grid power per winter. Heat pump would take 20+ years to pay itself. Double glazing probably 30-40 years.

To make same amount of solar power per year I need a single $130 NZD panel.