I live in the UK and have a Model 3 reservation. I'm looking at the benefits of a combination of installing solar panels, Powerwall and using cheaper overnight electricity (called Economy 7 in the UK). Due to our climate in the UK, solar payback periods are quite long and apart from weekends most of the generated electricity won't be usable and will be exported at about a third of the cost of buying it back. Powerwall 2 would solve this but payback on that at the moment is working out at just under the service life of the unit so I'm not convinced. There would definitely be savings if I could use Economy 7 electricity at night to charge the Tesla (I'll need about 10kwh per day Mon-Fri and more at the weekends) but the increased cost of peak usage on these tariffs may negate the gain. My commute is about 30 miles a day. A real cost benefit would be if I could use the spare capacity in my Tesla as a Powerwall when I'm not using it. If I could set a system up to allow me to specify the residual charge that must be kept in the Tesla (say 50%), I could use cheap electricity overnight to keep it fully charged, then when I come home, plug it in and draw power from the Tesla for powering the house until midnight, then use cheap electricity again to charge the whole thing up. This would be great for the grid as a whole, allowing energy companies to use more renewables due to the storage effect. I'm sure this isn't a new idea but I couldn't find anything online. Does anyone know whether / how this can be done?