Ask the experts: Solar and batteries

By Brandon Walton on July 3, 2015

Pairing your solar system with battery back up is a hot topic among solar customers. We spoke with several experts to get their take on what you should know before you add a battery to your system.

We’re pleased to have the input of Scott Sklar of the Stella Group, Anthony Colella of EDGE Energy, Michael Geaneas of Independent Solar Solutions, and Matt Powers of Virtue Solar.

What advice would you give to a solar customer considering battery storage?

Scott Sklar: Use experienced installers who have actually installed multiple battery systems. Ask for multiple references and contact those references.

Michael Geaneas: I urge customers to really analyze why they want battery storage, and consider if it worth the additional cost.

What do you see as the biggest benefit to backing up a solar system with a battery?

Matt Powers: I think the biggest benefit of a solar system with battery backup is the security of having round-the-clock power. There is a major advantage to having a power system that can potentially run for months without the grid.

Scott Sklar: Reliable electric power with the best electric power quality (no surges, sags, or transience). Why would you have thousands of dollars of solar that goes out when the electric grid goes down?

What is the biggest downside?

Anthony Colella: The biggest downside right now is technology — we need more early adopters to increase demand and push advancements towards smaller, more powerful, and longer-lasting battery technology. Most of today’s batteries will last at least 12+ years, but if we had a 30-year battery solution that could cover the demand of a heat pump (for at least short periods) at reasonable cost, we might install a battery system with every solar PV array.

Matt Powers: The biggest downside to a battery-backup system is the cost. While grid-tied systems typically have a strong return-on-investment over the life of the system, battery-backup systems do not. The true value of a battery-backup system lies in its unique functionality. For some homes and businesses, having constant, reliable power is most important.

How does adding a battery impact the solar installation process?

Michael Geaneas: There are additional wiring and components involved.  You also have to set a subpanel to run the loads you want backed up (similar to a generator).  From our experience it adds about a day to the installation.

Matt Powers: If you are interested in installing battery-backup, it’s best to start with the end in mind. Systems can be retro-fitted later, but it’s always ideal to know what the goal is right from the start. Depending on the equipment, installing battery backup systems can impact everything from how many panels are needed, the type of panel, the inverter used, and how the system interconnects to the grid. There is a significant amount of additional work and parts involved as well, so finding a location that can accommodate a battery-bank, balance of system, and inverter is important, since this location may be different than if you only needed space for an inverter.

Do you think battery offerings will become more common with panel installations?

Anthony Colella: Absolutely. Batteries are where solar was in this area about 4-5 years ago. We’ve got a few pioneers who are interested and getting it done, and demand will keep increasing as performance goes up, and prices go down. As installers, we need to start practicing ‘last year’ so that we can make it a process.

Michael Geaneas: Yes, as the battery technology continues to improve and the cost comes down battery back-up systems will become the norm.  Tesla will be manufacturing batteries at a scale we have not seen before, so that will naturally bring down the price due to economies of scale.

How have you seen battery technology improve over the past few years?

Anthony Colella: Right now, a battery system costs a good bit, but as an installer the biggest pain is that 3-day installation window with some very highly-skilled, -valued, and -educated employees. If manufacturers can ship units that are plug-n-play to reduce our installation time to 1 day with just 2-3 people, then that’s a huge win-win for the installer and consumer.

Michael Geaneas: Over the past few years there has not been much improvement to the traditional lead-acid deep cycle battery.  They have been basically the same for years.  When the new lithium-ion batteries hit the market then there will be a drastic improvement.

As battery technology improves, what potential is there to add batteries to an existing PV system in the future?

Anthony Colella: You can do it today fairly easily. Most of the plug-n-play units that are in R&D right now are supposed to be easily retrofitted to most any modern PV system. Furthermore, battery systems that we install today can have new batteries swapped in at any time. If the Lithium Ion’s are great a few years from now, then we just unplug the old ones, and swap the new ones in. Viola! More battery.

What impact will Tesla’s battery have on homeowners and businesses installing solar?

Anthony Colella: One great thing that will happen is that battery technology is going to rocket forward in performance, and come down in price. The best thing that may come out of it is just that being associated with Elon Musk and Tesla, the technology is going to reach so many more people than it has been reaching thus far, that it’s really going to transform the market. We’re already having “Powerwall Conversations” with almost every solar visit we do today, and I also trust that Tesla will over-engineer the Powerwall to such a degree that it’s just going to work for you hassle-free for years to come, and will also be a straightforward and quick installation for companies like us. It gives the consumer that “you can’t shut me down” ability which may be comfort for a homeowner, or ability to continue work safely for businesses.

How would you advise customers to optimize their use of the battery they purchase?

Scott Sklar: Customers should make sure to get color-coded, icon-based diagnostic systems for your battery system.

Anthony Colella: You need to work with the company who is designing and installing the system. Not all back-up systems are meant for regular powering or discharge, and not all power solutions are meant for intermittent backup. Let the designers know exactly what you want to power, what you need to power, and generally for how long at a time, so that you can get the right system. Otherwise, the charge controllers take care of optimization for you by float-charging the batteries and optimizing the life expectancy and power usage.