Powerwall is a daily use battery that is produced and marketed by
Tesla to provide power to homes or businesses for part of the day, off-setting
some electricity costs.(i] The issue that remains is the cost. How much does
Powerwall cost initially, how much does it cost to operate, how much
electricity will be offset, and how many years will it take to pay back the
initial capital and installation costs? These costs must be considered in order
to fairly compare our current electrical system to those that government
policies are promoting through their push for renewable sources of energy. This
article provides answers to those questions and a tool to estimate the payback
period based on local electricity costs.
Powerwall Cost and Operation
Buying a Powerwall and inverter, as well as having it
installed is estimated to cost $7,340
by SolarCity[ii] (like Tesla, Elon Musk is the CEO of SolarCity). The daily
use Powerwall for homes is rated at 7 kilowatt hours,[1] with round trip
battery efficiency estimated at 92 percent, and inverter efficiency estimated
at 95 percent. About 7.5 kilowatt hours is needed to charge the Powerwall,
providing about 6.5 kilowatt hours of power once charged….
As an example, assume peak rates at $0.15 per kilowatt hour
and off-peak rates at $0.06 per kilowatt hour. At the off-peak rate, it would
cost $0.45 to charge the Powerwall each night. Operating the Powerwall for 6.5
kilowatt hours the next day, saves $0.98 of electricity charges. Factoring in
the charging costs, saves $0.53 a day of electricity costs, or $193 a year, requiring a payback period of 38
years, which is almost 4 times the warranty period of 10 years for the
Powerwall.
If solar power was used to charge the Powerwall, it would
save the charging fee of $0.45 a day, making the Powerwall savings each year
$358. Factoring in the installed solar panel cost of$3,570[2]
for a 1.5 kilowatt system[iii], makes the payback period 31 years, still 3 times the warranty period.
Full text at: http://canadafreepress.com/article/77935
