My energy cost is $0.1649/kWh. The installed price of the two Powerwall units is $15k. I expect fully charge and discharge the Powerwall 300 days per year (based on historical average sunshine hours per month) and use 24kWh each night.

Based on these assumptions I calculate that: 300 days x 24 kWh x $0.1649 = $1187.28 per year so (15000/1187.28 =) 13 Years "pay back period".

The Warranty on the product is 10 Years and the useful life is claimed to be 15 years. However many people claim that the performance (storage capacity) will degrade down to 70% of original capacity after 10 years so this calculation should factor that in too ...

Is it economical to buy a Tesla Powerwall or simply pay "the grid" (our major energy supplier) for (renewable) power at night?

Are you a Powerwall owner? Have you done a similar calculation? What is the conclusion? #discuss!

Note: I'm a huge fan of what Elon is doing and have much love for Tesla as a company, but I want to know from a purely economic perspective, does it make sense to invest in a Powerwall?

For reference I've expanded on this calculation and included all the supporting research and references in: https://github.com/dwyl/home/issues/25