If you’re interested in backup power sources for your home, engineer Robert Brenner offers some great insights. Author of the book Power Out! How to Prepare for and Survive a Grid Collapse, he examines the pros and cons of alternative backup energy sources including the:
Of course, the winner is the SMA inverter that converts the direct current (DC) from your solar panels to the alternating current (AC) your home appliances require. The SMA inverter is how you get 1500 watts of usable AC from the sun.
The Tesla Powerwall is purported to provide 7 kWh for daily cycling or 10 kWh for backup. The Tesla Company claims the battery bank can generate 2,000 watts continuously and 3,300 watts for peak use.
The typical house consumes about 30 kWh every day. At a Powerwall discharge rate of 2 kW per hour, a 7kWh battery driving an inverter will generate AC for this home for under 4 hours before the battery is drained.
This may be acceptable at night when there is no other power source available. It’ll give you some AC to operate at minimum load, but the conversion efficiency of 0.94 during the charge and discharge cycles leaves me with more questions than answers.
An alternative is to use a $500 gas generator but the noise may be unacceptable.
Some home owners in Louisiana have had thieves sneak in early in the morning with a running gas lawn mower, set it next to their generator, then turn the generator off leaving the mower sound while they steal away with the homeowner’s emergency power source.
For years, Sunny Boy (SMA) had been trying to get U.S. government and utility bureaucrats to let them offer a solar-to-AC backup system that they had already designed.
Based on the precedence set by Japan [he Fukishima magnitude 9 earthquake], the U.S. stopped stonewalling SMA and today thousands of homes are getting solar with a TL inverter that provides a socket for 1500 watts (12.3 amps) of AC directly from the solar system.
Many homeowners with existing photovoltaic solar are investing about $2,400 to replace their own inverters with an SMA TL secure power product. They want that power loss insurance.
Source: Robert Brenner of Survival Life