i've heard of some business models that install these and have you pay what would be the difference to your electric bill to the company until they pay themselves off, not sure if the panels last long enough to make that work though
So no. 20kw is not the answer. I showed my setup: 3.5kw + big battery. Pays the bill approx 60 70% of the daily usage. Investment payback : 5years.
They're a terrible deal for those companies investors though.
Presumably at some point they go bankrupt and sell your roof at auction??? weird setup
A lot of the time such companies pray on people on stupid plans (or those paying thru the nose for "exclusively renewable") power.
(9 USD / kWh sounds terrifying. Not only an electric kettle begins to cost you; probably playing computer games at high quality / resolution comes with a noticeable price tag in electricity that the GPU would eat.)