The reason is avoiding doubling the the battery needs (car+house) when solar panels are available. A modern compact house with proper insulation and heat pump needs overnight less then 20 kwh in the worst winter days. Being able to use one quarter of the battery when the sun is down, recharged the day after, would be really money and environmentally effective. Why buying a fixed home battery like powerwall in a future where most of the time at least a mobile battery (a car) would always be connected to the home grid?
The reason is avoiding doubling the the battery needs (car+house) when solar panels are available. A modern compact house with proper insulation and heat pump needs overnight less then 20 kwh in the worst winter days. Being able to use one quarter of the battery when the sun is down, recharged the day after, would be really money and environmentally effective. Why buying a fixed home battery like powerwall in a future where most of the time at least a mobile battery (a car) would always be connected to the home grid?