When I was looking into this here in Seattle it looked like a minimum viable configuration would be at least 2 10KW Tesla batteries. About a year ago the cost was around 40k USD that included solar panels. I decided to pass on that deal as we rarely use on average about $70 in electricity per month.
That is insanely expensive and you would never recoup your investment. At least I will recoup mine fairly quickly plus never have power cuts ever again. We had an internal switch added this evening so I can rotate between the grid and solar. 8am -8pm using solar and then 8pm -8am using the grid for now.