There are many ways to store energy. Water may be pumped uphill or dammed to run turbines later; molten salt can store heat for slow release over many hours. Batteries are probably the most familiar energy storage method, and battery technology has improved tremendously over the past couple of decades—especially rechargeable batteries, which are now used in everything from cellphones to locomotives. But what about solar energy? How does one store that away for a rainy day?

Due to the increased global demand for solar installation, Tesla has begun developing Powerwall batteries specifically for use with rooftop solar systems. LA Solar Group also offers sonnen eco storage battery solutions. Both batteries can store energy from your solar panels, from the electric grid, or even your plug-in electric vehicle. Here is a basic overview of both models:

Tesla Powerwall

The lithium-ion Powerwall battery comes in one size: a 44” h x 29” w x 5.5” d 270-pound unit that can be used indoors or outdoors, mounted on the floor or a wall. It can store up to 13.2 kWh of energy, and as many as ten can be used together. The price starts at $7,000 plus installation, but battery prices tend to drop quickly, so check with us for the latest. Tesla also makes the larger Powerpack for business and governmental use.

Note: Tesla updated the Powerwall’s specs and housing in 2016, and sometimes refers to it as Powerwall 2.0.

sonnenBatterie

German energy giant, sonnen, uses Sony lithium-iron phosphate batteries in its eco line for residential energy storage. It claims its battery chemistry is especially safe and well-suited for use with rooftop solar. Sonnen gets points for a modular approach, offering sizes ranging from 4 kWh to 16 KWh in 2 kWh steps. That’s six different capacity levels. These are divided into two unit sizes:

  • 51” h x 26” w x 14” d housings for the 4, 6, and 8 kWh batteries
  • 71” h x 26” w x 14” d housings for the 10, 12, and 14 kWh batteries  

Sonnen shows its eco line deployed in a variety of indoor and outdoor settings, both floor and wall-mounted. Because unit weights range from 121 to 600 pounds, you’ll need more than a studfinder to get the bigger units up securely, but we’ll handle that for you.

The eco line starts at about $9,500 plus installation. It also offers a compact line of batteries priced 20% lower that are designed exclusively for self-consumption (not as backup in an outage). Again, price quotes on batteries can really vary, so as part of your research, give us a call.

There are many benefits to residential energy storage. Having a battery for your home means you’ll never be without power. It helps you pay the lowest possible price for electricity at all times. It lets you say goodbye to your electric utility, if you’re so inclined. And in some cases you can even get a rebate on your purchase. Let’s examine each of these benefits in a bit more detail.

Having a Battery for Your Home Means You’re Never Without Power

Energy storage solves the problem of intermittency that comes with using sun or wind-power, providing electricity in dark or calm conditions. In the case of your rooftop solar system, your battery will power your home at night after the sun goes down. There’s also a sense of security in having that power on tap: Should there be a power outage on the electrical grid in your area, your lights will never flicker. You won’t have to fire up a generator or light a single candle, unless you’re in the mood. When needed, the switch is near-instant. In the case of an extended outage, you’re likely to become a very popular neighbor very quickly.

You’ll Always Pay the Lowest Possible Electric Rate

The Tesla Powerwall and sonnen eco have software to handle the flow of energy between your solar panels, the electric grid, and–if you own an electric vehicle–your car. This software helps you choose the best times to charge and discharge power at the most efficient rate. One of the great things about this system is that it keeps an eye not only on efficiency, but on costs. You can charge your battery with power from your panels for free, and use it as needed instead of high-priced power from the electrical grid. That’s especially useful If your utility bills are based on time of use, with prices that spike during peak hours.

Your battery is also an alternative to selling excess power to the grid. If you’re producing more energy from your rooftop solar system than you’re using, and exporting it to the electrical grid, your utility bill credit or check will depend on your net metering terms. Depending on what those are, you may be better off storing it for yourself for later use.

If You’re Going Off-Grid, You’ll Want a Battery

The idea of getting rid of your utility bills once and for all, whether you’re in a remote area or in downtown LA, is enormously appealing. However, unless you plan on going full Thoreau, you’ll probably still want electricity for hot water or the occasional Netflix binge. That means your system will need to produce an average of 8MWh per year, according to the US Energy Information Administration. With solar and storage, you can generate your own electricity from the sun, store it for nighttime use, and eventually kiss your utility bills goodbye.

Rebates Are Available Now for Residential Energy Storage  

Thanks to a program funded by the California Public Utility Commission (CPUC), there are rebates available right now to help homeowners buy energy storage batteries. These rebates can be used in a number of solar scenarios: when you install your rooftop solar system, as an add-on to an existing system, or as a standalone solution used without rooftop solar (charged by your household electricity feed from the utility just like any other electric appliance).

Like a lot of renewable energy incentives, the Self-Generation Incentive Program (SGIP) offers the best deals for the earliest applicants. Phase 1 of the program offers rebates of $0.50 per battery Watt-hours. Phase 2 begins June 5th, when the rebate drops to $0.40/Wh. Phase 3 starts in a few weeks, and will drop the rate to $0.30/Wh. Phases 4 and 5 will be commensurately lower. As we mentioned in our ultimate 2017 guide to solar incentives, getting started sooner means higher rebates.

LA Solar Group Can Answer Your Storage Battery Questions

Tesla Powerwall and sonnen eco storage battery solutions are both available in different sizes and formations so that you can add capacity over time. The Powerwall’s attractive affordability may be a factor in your decision, but you can tailor combinations of sonnen’s modular units to suit your needs more precisely, which may yield better financial results over time. Choosing a battery make and model is important, but there are other important factors to consider in an energy storage project. Many companies cover battery selection in only the briefest of terms, without consulting you first. That should give you pause.

In the end, deciding which system is best for you will require considering your energy usage, costs, rebates/incentives, system size, warranty, TCO, and payback horizon. To safely and efficiently install this high-voltage equipment, it is best to consult with experienced electricians who know their way around a roof. LA Solar Group is a CSLB C-10 licensed electrical contractor and CSLB C-46 licensed solar contractor. We’re also experienced roofers, and have been dedicated to helping homeowners all over the Southland for over a decade. If you’re considering going solar and have questions about energy storage — or if you want a battery without solar and want to know your wiring requirements — we’re here to help.