Since last spring when Elon Musk publicly pre-announced the market arrival of the Tesla Powerwall, the battery question is one of the most frequent questions that we have been fielding from potential customers. To answer it, let’s back up a bit and put some context around solar and battery systems in the US.
Solar plus battery systems are not new. People have been installing solar with batteries for over 40 years. The need for batteries has traditionally been justified by homes or electrical loads with no grid connection, where batteries are necessary to store energy for use at night. These off-grid systems are typically custom built and consist of several batteries, specialized inverters, and charge controllers.
NATiVE has been installing solar systems with batteries throughout Texas since 2008. While we have designed and built off-grid systems, the bulk of our battery systems are also grid tied. The primary motivation for these systems is to provide backup power to critical loads in the case of a grid outage. While grid-tied systems are the most economical way to install solar on your home, they have one functional drawback: when the grid goes down, the solar system shuts down. Electrical code requires this functionality to protect any linemen working on the grid.
To maintain power in the case of a grid outage requires a grid-tied battery backup system with a critical load panel and batteries. This is not a new application, but it represents a small percentage of the systems that we install – mainly because the initial cost is high and grid reliability is not a primary concern for most homeowners. In this arrangement, when the grid goes down, the power to critical loads automatically switches to the battery/solar backup source. In almost all cases, there are only a few circuits that are backed up, typically refrigerators, well/rainwater pumps, and a few lights and plugs.
So, what has changed? Why is there so much discussion now around batteries?