Can You Add Batteries to Your Existing Solar System?
For years, batteries have been a way to store excess power for solar systems. But until recently, they only made sense for a few, mostly off-grid solar systems due to their high cost and low efficiencies. However, as battery continue to decline and batteries become more and more effective, they are also becoming a viable option for many grid-tied solar systems.
Batteries may not have made sense if you installed your system a few years ago. But as the market changes and technology advances, you may find yourself wishing you could take advantage of energy storage.
If you’re wondering whether or not you can install batteries in your existing solar system, the answer is yes! There are several ways you can integrate battery power into your existing solar system.
How Do Solar Batteries Work?
Before we get into your options for adding batteries onto your system, we want to quickly go over how batteries work.
As the sun shines, your solar panels collect the energy and turn it into DC electricity. The electricity is then sent to your inverter, which converts that power into AC electricity – the form you can use in your home or business. As your system produces energy, it’s used to power your lights, appliances, and devices. But what happens when your system produces more electricity than you use?
If you install a battery, here’s where it comes in. When you’re using more electricity than your solar system is producing, you can draw on energy stored in a battery instead of drawing it from the grid.
Adding a Battery to Your Existing Solar System
In most cases, adding a battery to an existing grid-tied solar system is possible, however, the level of difficulty is dependent on whether or not your system was designed with the intention to do so. Here are the ways to install a battery in your existing solar system.
Storage-Ready Solar System
Best-case scenario, you knew you’d eventually want to install batteries and planned for it when having your system installed. Maybe you were waiting for to drop or wanted to keep the upfront investment during installation as low as possible. Either way, you prepared yourself for the future. Your inverter is ready for the installation of a battery when it makes financial sense to you. This is the cheapest and easiest option, requiring less labor and materials than the other two options.
If you did not install a storage-ready system, there are two main ways to integrate your battery into your system – DC Coupled and AC Coupled.
DC Coupled System
With a DC Coupled System, your inverter will be replaced by one that works with a battery and a solar system. These are known as hybrid inverters. DC power produced by your solar panels is used to charge the battery. From there, the power is passed through the hybrid inverter, which converts the power into AC electricity. Then, the AC power can be used either in your home or business or go to the grid.
If you go this route, your system will lose less of the energy produced by your panels during the conversion process. This is because power is only going from DC to AC, whereas in an AC Coupled System (explained next), all energy stored in the battery goes from AC to DC (to charge the battery) and back to AC again. However, this option will likely cost more upfront due to the cost of the inverter and more involved labor.
DC Coupling could be a great option for you if you’ve had your solar system for some time and your inverter is approaching the end of its expected life. Most string inverters last fifteen years, so replacing your inverter a little earlier with one that works with a battery could be to your benefit.
AC Coupled System
The next option, an AC Coupled System, uses your traditional inverter in addition to a second inverter, or a “storage inverter,” that charges the battery. DC power produced by your panels goes to the inverter and is converted to AC power as it always has. From there, the inverter sends it to your building if you’re using electricity, to your battery if you’re producing more electricity than you’re using, or to the grid if your battery is fully charged.
Typically easier to install, AC Coupling offers flexibility in terms of location, works with a variety of inverters, and is likely to be a lower-cost option. However, it is slightly less efficient. Electricity stored on the grid and used in your home is AC, but batteries store DC power. For the battery to provide power you can use in your home or business, it must then be converted to AC power. This extra step causes more energy to be lost compared to DC Coupling.
Does Installing Batteries Make Sense for You?
One benefit of installing batteries is your ability to access electricity when there is a power outage in your area. Though this could be an important benefit to you, there are a few other things to consider when deciding whether or not adding batteries to your solar system is the right choice.
Some utilities charge time-of-use (TOU) rates. These rates fluctuate depending on the time of day. When electricity demand is higher (often in the afternoon and early evening), you pay more per kWh than what you would when fewer people are using electricity (like at 3 a.m.). If you have batteries with your solar system, you can help avoid paying these increased rates by drawing on the stored energy in your batteries.
Similarly, demand charges are fees levied on the customer based on the period they use the most electricity or their usage during a peak period. It is based on the highest amount of power reached during a specific time interval. That fee is added to the customers’ bill. These are typically associated with commercial and industrial facilities, not residences.
These extra costs can add up, and a battery can help mitigate these fees. By drawing on power stored in your battery during times of high demand, you can reduce these extra fees.
However, if you don’t have these fees, you may want to rethink if it’s a worthwhile investment. While decreasing your reliance on the grid may seem attractive, net metering is a cost-effective way to access power when your solar system isn’t producing. Check out the Policy Overview from the National Conference of State Legislatures to find out your state’s policy on net metering.
Though batteries are quickly coming down in price, a cheaper option for a backup energy source is a generator. Generators of various brands and models can be purchased at your local hardware store and can be transported to various locations. However, they are limited by the amount of fuel you can store and transport. For more on the comparison of batteries and generators, check out this blog.
Most generators can also be transported and used at your location of choice. This makes it easy to supply power wherever you need it. You’re just limited to the amount of fuel you’re able to store and transport.
When deciding if adding a battery to your existing solar system is right for you, there are many things to consider. Give us a call or send us a message to discuss your options!
Product Spotlight: the Sunrun Brightbox Home Battery
This post may contain affiliate links from the Amazon Associate program.
If you’ve taken the time to invest in solar panels, you should also invest in a battery as well. The sunrun brightbox battery provides your home with backup power. This way, if your power or your grid goes down: your power will not! This maximizes savings in utility territories that have time-of-use rates or unfavorable net metering policies.
This brings forth a great product to invest in: the Sunrun Brightbox Home Battery.
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How Does This Work?
To put it simply, these batteries work with storing energy. Your solar panels collect solar energy. The panels take in the sun’s energy to create a direct current (DC) electricity. However, most homes run on an alternate current (AC) energy. Therefore, the DC energy is converted to AC electricity through an inverter.
A solar inverter converts direct current to alternate current. This allows the inverter to tie to the grid. This way, you have the ability to run this electricity through your home and appliances. Think of the inverter like the brains of the solar panels. Inverters also have the ability to operate at an optimal performance level. This way, you can do data monitoring, use utility controls, and have engineering for system design and applications.
Once the inverter has transformed the DC to AC and electricity is running through your home, solar panels can’t act as the backup in case electricity goes out. Electricity going out can be unpredictable, like if a car accident causes the area to go out, or it could be predictable during inclement weather. It’s also important to know that solar energy can’t be used during power outages in case there are repairs attempting to restore the power. This is for the safety of the repairmen. One thing that should be predictable is that a solar power battery, like the Sunrun Brightbox, can save the day.
Solar Batteries During an Outage
An off the grid structure cannot always keep up with the demands of a society that is constantly plugged in. Generators can offer a temporary solution. However, they can be dirty, noisy and dangerous. Combat this problem with a solar battery. This solution is independent to your home, safe, simple and clean.
About the Sunrun Brightbox Home Battery
The Sunrun Brightbox package is made with LG Chem batteries. These batteries are curated from lithium ions, and come in different sizes. These batteries have the ability to provide over 10 hours of backup in case the grid is not operable.
This battery does come at a price between 6,500 and 8,000. This does not include the initial 1,000 cost for installation or for any solar panels. However, if you aren’t ready to buy this product, you have the ability to lease it. Leasing the battery comes with a 20 year full service plan. Whether you buy or lease, this battery has a warranty of 10 years, assuring customers that the battery hasn’t lost more than 40% of storage capacity during the warranty backed 10 years.
Where is the Sunrun Brightbox Available for Purchase?
Unfortunately, the Sunrun Brightbox is not currently available in all 50 states. These are the current locations it is offered as of January 2021:
- Arizona
- California
- Colorado
- Connecticut
- Florida
- Hawaii
- Illinois
- Maryland
- New Mexico
- Massachusetts
- New Hampshire
- Puerto Rico
- New York
- Rhode Island
- New Jersey
- Nevada
- South Carolina
- Texas
- Washington D.C.
- Vermont
There are 13,000 units used across America currently. Between May and September of 2020, existing customers used their Brightbox for essential needs during grid outages. In those four months, the batteries were used for a total of 7,583 hours, or roughly 315 days.
Do you Have Solar Power Yet?
Solar power is the way our future should run. This clean, renewable energy source allows you to reduce your carbon footprint and your electricity bill. With all the companies out there that work with solar panels, it might be difficult to decide which company to go with. But, look no further! At ONIT, we have over a decade of experience with helping homeowners find the perfect products and services.
There are plenty of reasons to switch to solar energy. The benefits of switching to this clean energy source includes:
- Cheaper energy
- Increased home value
- Long-lasting
- Works even on cloudy days
- Finally, solar panels are better for the environment
We understand that solar energy can be confusing if you’re not familiar with key terms. That’s where we come in to help! Between our amateur’s guide to solar power and our knowledged staff, we are here for all your questions. Call us today at 1-833-433-0331 to learn more about how ONIT can help you set up your solar panel and make your life cleaner and easier.
Interested in learning more about how solar solutions can benefit your home? Reach out to the professionals at ONIT for a personalized quote. ONIT’s expert team can help make your green energy goals a reality. And when you install a solar power system with ONIT Home, you can install a whole home water filtration system and Smart security system for FREE with installation in two weeks. Contact us today at 1-833-433-0331 to learn how you can enjoy this special offer.
The path toward solar, batteries and generators working together on whole home energy resilience and grid independence
The two primary drivers for a homeowner to make a significant investment in home energy management equipment are resilience and economics of self-generation. Environmental benefits are always a nice bonus but rarely a primary driver, except for some very early solar adopters with disposable income.
Historically, home standby generators have been deployed for resilience, while solar and solar battery storage systems have primarily aimed at utility bill minimization.
Against the backdrop of a total addressable residential market of about 77 million homes in the United States, progress has been made leveraging both primary drivers (using Sunrun and Generac investor presentation data):
- On the self-generation track, current market penetration for solar is ~4% of households with ~3 million systems deployed. At a ~15% storage attach rate, approximately 450,000 systems include storage (~1% penetration).
- On the resilience track, with ~3.9 million units, traditional home standby generators have achieved a market penetration of ~5%.
Clearly, solar and backup technologies have just begun to scratch the surface. The untapped market potential represents a blue-ocean opportunity that undoubtedly will be hotly contested at every link in the value chain.
Two roads converging
Today’s homeowners are presented with a host of options and choices to address their need for both home energy cost minimization and energy resilience during grid outages.
Currently, a resilience-driven homeowner likely still gravitates to buying a home standby generator as insurance against grid outages. This unfortunately has no positive effect on their electricity bill, or the environment.
Meanwhile, a homeowner focused on utility bill minimization might initially buy a solar system and later add batteries with expectations of energy resilience during a grid outage. Most homeowners likely don’t understand the resilience limitations provided by batteries.
Tomorrow’s customers will expect a comprehensive whole home energy management solution and a seamless customer experience throughout their entire journey from initial engagement to ongoing post-sales support for their system.
In the context of comprehensive whole home energy resilience and grid independence, offering a prospective customer a solar or solar storage system alone is like selling a 4-ft blanket to a 6-ft person to stay warm. Any way you slice it, something will be cold:
- Deploying only solar addresses the economic dimension of “grid independence” but leaves the short-duration and long-duration backup “energy resilience” requirements uncovered.
- Adding storage covers short-duration backup but is uneconomical for prolonged outages with insufficient sunshine.
The missing 2 ft of the energy resilience blanket — the long-duration backup gap — can be cost-effectively and eco-friendly addressed by adding a clean, safe and efficient generator that operates intermittently. Think of energy storage paired with a generator as a never-empty battery, or as solar panels that work at night.
The road ahead
If you are an independent home energy contractor, you are already living in interesting times. Equipment manufacturers for solar, batteries and generators are pursuing you to align your business with their brand and technology. You are also competing against national solar installers on a mission to accumulate control over as many residential rooftops as possible to become relevant players in the virtual power plant arena.
On the technology front, the convergence of solar, batteries and generators into a well integrated, comprehensive whole home energy solution still has a long road ahead. Look no further than the number of boxes and conduit involved in an average system installation.
While system technology is converging, you are seeing your fellow installers experimenting with a variety of diverging business models and functional specializations, deciding to outsource different parts of the value chain. While some FOCUS on lead generation and sales, others specialize on installation or post-sales service.
The U.S. market for home energy management is most certainly not homogeneous. Evolving utility posture and state-specific incentives determine economic attractiveness, while resilience requirements are heavily driven by wildfires, hurricanes and other extreme weather events. In short, the most attractive state markets are the spot in the Venn diagram where renewable-friendly and disaster-prone environments overlap.
So, what is your path forward?
Upstart has a survey to learn more about home energy contractor views on whole home energy resilience and grid independence. Every survey participant will receive a copy of the overall results. Start survey here.
Комментарии и мнения владельцев
Good article! I agree that integrating a generator with a renewable energy system is not straight-forward. But at Enphase Energy, we already offer a scalable, residential system where the residential microgrid has PV, storage and the generator working simultaneously in harmony. The system is configurable to have the generator kick in whenever there is an outage, or operate the generator only when the SoC of the batteries are low, then transfer back when the SoC is high. One additional point I would add is that people don’t realize that in extreme conditions like super storm Sandy (which I survived in NJ) or the California fires, (where I was evacuated in CA), mostly likely you won’t have access to fuel. I couldn’t fill up my car and the gas lines were cut off. So, even stand-by generators would’ve been useless. Ultimately, you’ll have to have a fuel reserve, or lots and lots of batteries to get through a week-long blizzard.
In the extreme northern and southern parts of the planet solar energy, including storage, only works for a little over half the year. What else is available? Wind? Heat pumps? Efficiency of electric appliances? Lots to consider.
What to expect from California’s new rooftop-solar plan? batteries
California is about to dump its net-metering regime and adopt a new system that emphasizes home batteries. Here’s how companies are preparing.
Canary Media’s Down to the Wire column tackles the more complicated challenges of decarbonizing our energy systems.
This is part one of a three-part Down to the Wire series this week digging into a new rooftop-solar policy expected to be adopted by the California Public Utilities Commission on December 15. 2022. [ UPDATE : The policy was adopted by the CPUC as anticipated.]
Vincent Battaglia, CEO and founder of Renova Energy, isn’t shy about expressing his feelings on California’s looming decision to end the net-metering regime that’s driven a nation-leading 12 gigawatts of rooftop-solar installations in the state and helped his company grow from a sole proprietorship in 2006 to more than 300 employees and 65 million in annual revenue today.
“ Bullshit” is how Battaglia characterizes the “ cost-shift” argument made by California utilities and consumer advocates contending that existing net-metering policy has unfairly shifted the costs of maintaining the state’s grid from people rich enough to buy or finance rooftop-solar systems to those who can’t afford them. He blames utilities for the lion’s share of rising electricity costs instead.
And he thinks the new structure proposed by the California Public Utilities Commission, which would reduce compensation for exported rooftop solar power based on hourly measurements of its value to the grid, is ridiculous for being based on an “ asinine set of incremental adjustments of every frickin’ hour of every day.” He fears the structure will make the cost-effectiveness of every new solar system a mystery for homeowners, installers and financiers alike.
But no matter how Battaglia feels — and his point of view is far from unique among California rooftop-solar industry players, even if it is more colorfully expressed than most — he’s still planning for how to keep his business growing once net metering goes away in California next year, as it will if the CPUC approves its proposed structure at its meeting this Thursday. And there’s more to his plan than expanding into neighboring states like Nevada and Arizona, he said.
First, “ we’ll be adjusting our pricing so that our customers are not looking at a nine-year payback,” he said. Under the current net-metering structure, a homeowner who installs a new rooftop solar system can expect to recoup the cost in five to seven years through reduced electricity bills and credits for exporting their excess power to the grid.
The CPUC ’s new structure has set a target of nine years for customer payback, but Battaglia wants to get that number closer to seven for his customers.
“ In 18 months, when the utility does another double-digit rate increase” — an offhand reference to California’s spiraling retail electricity rates, which have risen between 15 and 33 percent since January 2020 — “ that pricing will look even better,” he said.
Second, Renova will double down on selling batteries alongside new solar systems, he said. Those batteries can store solar power generated at midday, when it’s worth little to customers or to California’s grid, and save it for the evening “ peak” hours after the sun goes down, when the state faces increasing threats of power demand exceeding supply.
Renova is sourcing batteries from SunPower, a minority investor in Battaglia’s company. “ Those batteries are very clever with their software,” he said, capable of forecasting when they should store power and when they should discharge to lower a home’s grid draw or export power back to the grid. And because the CPUC ’s proposed new structure would offer extra-high value during a relative handful of hours of the year, being able to predict that is vital to make up for the big drop in compensation they’ll face almost every other hour of the year.
Those are also the hours when the CPUC and other state agencies hope that solar and batteries can support all the other grid-powered devices — electric vehicles are a big one, as are heat pumps for space and water heating — that Californians must adopt to reduce carbon emissions and meet the state’s mandate to achieve net-zero carbon by 2045.
In this respect, Battaglia’s plan largely aligns with broader state policy. The CPUC ’s stated goal with its net-metering replacement plan is to shift a largely solar-only market to one dominated by solar panels plus batteries — plus EVs, plus electric heating and appliances — all responding to and being rewarded for acting in ways that shift and shape their generation and consumption of power to support the grid at large.
Renova’s roadmap also mirrors the strategies being developed by a host of other companies whose businesses will be affected by the coming policy change, including nationwide solar installers Sunrun, Sunnova and SunPower, solar-inverter providers Enphase and SolarEdge, and battery vendors such as Tesla, LG Energy Solution, Panasonic, sonnen and Generac. They’re all looking at the still-uncertain details of how California’s new regime will work, both in isolation and in conjunction with multiple other policy shifts underway in the state.
“ We’re kind of in the Wild West of this new form of customer adoption,” said Walker Wright, vice president of public policy at Sunrun, the country’s leading residential solar installer. “ How can we get ratepayer value, resiliency value, out of a solar-plus-storage future in California?”
Moving beyond net metering
To understand why batteries will be so important as the rooftop-solar market changes under the CPUC ’s expected decision, it’s important to know how rooftop solar makes money for homeowners. In simple terms, that happens in two ways: by reducing how much electricity customers buy from utilities and by allowing customers to sell excess solar power back to utilities.
Today, both of those values are based on the retail rates that customers pay for utility power. Customers avoid paying those retail rates for every kilowatt-hour of rooftop-solar power that replaces a kilowatt-hour they would have used from the grid. They also get paid the retail rates for every kilowatt-hour of solar generated in excess of their usage that feeds back to the grid. (In the end, they pay for their “ net” usage of electricity, hence the term net metering.) According to the California Solar and Storage Association ( CALSSA ), the payback on most net-metered solar systems in the state is split pretty evenly between those two value streams.
Retail electricity rates are much higher in California than in other parts of the country, due to a number of factors. And, like everywhere in the country, they’re also much higher than the for power on wholesale power markets. That’s because retail rates encompass costs for lots of things beyond electricity, like the expenses of building transmission lines and other grid assets, hardening the grid against the threat of sparking wildfires, investing in energy-efficiency programs and offering subsidies to low-income customers.
It’s that gap between the portion of rates that pays for the cost of generating electricity and the portion that pays for all those other things that causes so much strife and confusion over net metering.
Utilities in California and across the country — and some consumer advocates and environmental groups — argue that net metering at full retail rates allows people with rooftop solar to avoid paying their fair share of all the costs for things that they still benefit from, starting with the grid that provides them power when their solar systems don’t. That, critics of net metering say, forces an unfair and unsustainable share of those costs onto people who don’t have solar.
Rooftop-solar advocates and their environmental and community allies argue that those costs are outweighed by the benefits of widespread rooftop solar. Those include tapping private-sector investment to replace fossil-fueled power faster than utilities would do on their own, reducing the need for new grid infrastructure by generating more power closer to where it’s used, and giving customers who want to switch to electric vehicles and heating a resource that can help cover the higher costs of making that switch, among others. They also argue that utilities are overestimating the so-called “ cost shift” from solar to non-solar customers in the service of a more fundamental interest: protecting their monopoly over the generation and provision of power.
We’ve written multiple articles and hosted a debate on the fractious arguments over these “ cost-shift” calculations, and won’t spend more time on them here. Suffice it to say that the CPUC has agreed with utilities and their allies that full retail-rate net metering is causing a cost shift, and its proposed decision aims to correct it. The CPUC ’s solution, which will apply to new solar customers starting as early as April 2023 (existing customers are exempted), is to change both the rates that solar-equipped customers pay for power and the rates they earn for exporting power, to more accurately reflect the costs and benefits of each. And both of these changes make energy storage an integral part of a moneymaking rooftop-solar proposition.
Why batteries are central to navigating California’s rooftop-solar future
For the power that new rooftop-solar owners buy from the grid, the CPUC ’s plan would require them to pay “ electrification rates,” dubbed as such because they’re intended to help homeowners move away from fossil gas and electrify their homes. In general, those are rate structures that charge more for power during peak hours (evenings from about 5 p.m. to 9 p.m.) and less during off-peak hours (the rest of the time). The aim is to encourage customers to use less energy during peak hours and then, during non-peak hours, store up solar power in batteries so it can be released during peak hours to lessen demand and strain on the grid.
Here’s a chart of current electrification rates for California’s big three investor-owned utilities — Pacific Gas Electric, Southern California Edison and San Diego Gas Electric.
Most of the customers of these utilities are already on “ time-of-use” rates that charge more during peak hours. But electrification rates have higher on-peak and lower off-peak prices, which reward customers who can control their consumption and generation to maximize value, but punish customers who can’t.
For the power that new solar owners export and sell to the grid, the CPUC would replace retail-rate compensation with compensation on an “ avoided-cost” basis — a complicated structure meant to reflect the value of exported power from hour to hour across different months of the year and different climate zones across the state. The following charts show how those values will shift over months of the year and hours of the day in a temperate climate zone within PG E’s service territory, indicating the wide variation in values that exported solar power can expect to receive over time. (The items listed in the legends are “ costs” that the state can avoid by tapping into rooftop solar power.)
The problem with both of these changes, solar advocates say, is that they replace stable and predictable values with changing and unpredictable ones.
That’s less of a problem for the power that rooftop-solar owners buy from the grid. The three utilities’ electrification rates are fairly comprehensible and predictable for homeowners and solar companies looking to game out their potential savings. Still, each utility’s electrification rate is different, so there’s a lack of consistency across the state.
What’s more, an ongoing CPUC proceeding to “ advance demand flexibility through electric rates” could well alter those rates in future years by changing the hour-by-hour structures on offer to solar customers or by adding new monthly charges in an attempt to spread fixed utility costs more evenly across all customers.
But those concerns pale in comparison to solar advocates’ anger over the changes proposed on the export side of the equation. First, the avoided-cost rates the CPUC would have solar-equipped customers earn for their exported power are far lower on average than today’s retail rates — about 75 percent lower, according to CALSSA — which cuts deeply into roughly half of a rooftop-solar system’s total economic value.
Get Caught Up
Can the US manufacture enough solar panels to meet its surging demand?
Managing that load shape will spell the difference between earning a reasonable payback on your investment in a solar array or not. While Jammal hopes that the CPUC will alter its proposal to enable standalone rooftop solar to achieve reasonable economic rewards, “ ultimately we think solar-plus-batteries will be the direction the market will go,” he said. “ What we are going to see — and we’re all going to learn this — is how our partners on the installation side start combining batteries and start combining these electrification products that have their own incentives and their own impacts on whole-home energy use.”
Is the industry ready for a boom in demand for batteries?
All of these changes add up to huge opportunities for battery vendors and the host of companies that are integrating batteries into residential solar.
Sunrun was ahead of most installers in marketing batteries alongside solar systems. It’s had particular success in California, where existing rate structures have already been encouraging home storage, and the risks of wildfire-prevention blackouts have made many customers seek out batteries to serve as backup power sources. The company says batteries are added to about 20 percent of the residential solar systems they install in California, compared to an industry average of about 14 percent in the state.
The CPUC ’s forthcoming decision, meant to supercharge adoption of batteries with solar systems, could quickly drive those adoption rates far higher, said Sunrun’s Wright. But it’s unclear whether the state’s utilities, regulators and permitting agencies are ready to efficiently support the shift to a far greater number of solar-battery systems than the state has seen before — and whether the broader battery industry and supply chain is geared up to support it.
California has deployed more than 530 megawatts of residential battery systems over the past five years, and demand is growing, Wright said. In fact, “ there’s far more demand for batteries than the industry can deliver right now, due to well-known battery shortages,” he said.
Solving those supply bottlenecks will be the first challenge for a post-net-metering California market. Recent market signals do indicate that a long-running shortage of batteries for grid energy storage, caused by Covid-related supply-chain disruptions and booming demand for lithium-ion batteries for EVs, may be easing, said James West, senior managing director and head of sustainable technologies and clean energy research at Evercore ISI.
“ We had a time there where the companies that were financing a lot of this, like Sunrun and Sunnova, and the technology providers like Enphase and SunPower, were short on batteries,” he said. “ Now they’re able to provide the batteries, at least in a reasonable amount of time.”
Once they can get the batteries, the next question for solar companies is whether they can get them permitted and interconnected in a timely fashion, Wright said. “ How quickly can you ramp up what is a profound change in the types and…volumes of applications that are coming in?”
Industry data indicates that it takes about 50 percent longer to permit and interconnect battery-solar systems than it does for solar systems alone, he noted. Many city and county permitting offices are still learning how to process these requests, although efforts to standardize solar permitting processes, including the Department of Energy’s SolarApp, could be adapted to support solar-plus-battery installations.
Another challenge is that adding batteries is more likely to trigger the need to upgrade a home’s main electrical panel, a process that can add months of additional permitting and interconnection time, Wright said. And customers who install rooftop solar are likely also to be “ in the front of the pack in terms of electrifying their homes and having EVs in their garages,” which will add complications to interconnection and permitting.
EVs and electric heating could add significant new loads to the utility grid — and rooftop solar panels could offer significant relief to those stresses, he said. But “ how can we get there, and can the system digest that change, and at what speed?”
Making solar-battery systems make economic sense
It’s also important to remember that batteries cost thousands of dollars on top of the cost of a typical home solar installation. Earning back the cost of a battery is far more complicated than plugging it in, programming it to store power at midday and discharge when peak begin, and walking away.
That’s why almost every solar-plus-battery system now being sold in California comes with a variety of options for actively controlling and adjusting the interplay of solar generation, energy storage and home electricity use to maximize the overall value of that “ load shape.” Just what that optimization will look like depends, of course, on a number of factors.
Some of them are starting to become clear — the need to limit exports during off-peak hours and save up energy to discharge when the value of energy exports spike, for example. But others will only emerge in the future, which means that these systems have to be ready to react to change.
That’s the idea behind sonnenConnect, the new “ grid-interactive” solar-battery program from sonnen, the German battery vendor owned by Shell, and Baker Electric Home Energy, a subsidiary of electrical contractor Baker Electric. It’s one of a growing number of “ virtual power plant” offerings that are promising customers increased value for their solar-plus-battery systems, in exchange for letting the installing company control how those batteries operate on a moment-by-moment basis.
“ This is about harnessing solar and harmonizing it into grid operations in order to enable the energy transition,” said Blake Richetta, CEO of sonnen’s U.S. business. “ To become a firm grid asset, you have to develop this kind of mechanism. Otherwise, you have tens of thousands of batteries doing nothing, sitting in backup-power mode.”
Sonnen has been operating these kinds of residential solar-battery virtual power plants in Germany since 2015. and it has structured similar arrangements in Utah with utility Rocky Mountain Power and in California for some apartment complexes.
SonnenConnect’s value proposition for homeowners and the grid at large is only partly defined at present, Richetta said. The most obvious value will come from balancing a home’s load shape against time-of-use rates and electrification rates, which is a relatively simple matter of scheduling when batteries charge up and discharge against known daily cycles.
But those daily schedules can change unexpectedly, he said. One major example of that is when California’s grid is on the verge of collapse, as happened in the summer of 2020 and again in September of this year, when grid operator CAISO had to institute emergency measures to reduce electricity consumption to prevent heat-wave-driven electricity demand from outstripping available supply.
During these emergencies, stored battery power is far more valuable to the grid at the tail end of a 5 – 9 p.m. peak period, after the sun goes down, than at the beginning, when the grid hasn’t yet reached its highest point of stress, he noted. But battery systems that aren’t programmed with this fact in mind might start discharging power at 5 p.m., leaving them depleted later on when they’re really needed.
Companies including sonnen, Sunnova, Sunrun and Tesla are already signing up customers willing to let those companies actively control their batteries to manage these later-evening demand spikes. The avoided-cost rates for energy exports would offer more money for those key hours, which could make it worthwhile to save up as much energy as possible and inject it into the grid at those precise times, he said. That’s just one of a growing number of ways that centrally controlled and orchestrated solar-battery systems can boost their value for their owners and the grid, Richetta said.
There’s clear value in a future of rooftop-solar-and-battery systems that can deliver that power when the grid needs it most, he said. That value shows up in modeling that indicates that the right combination of distributed solar-plus-storage systems can reduce the costs of getting to a 100 percent carbon-free grid by tens of billions or even hundreds of billions of dollars, compared to relying solely on utility-scale clean energy and batteries and high-voltage transmission grids.
“ If there are aggregations of future solar-plus-storage systems across the state, the system should be able to find value from them during peak times,” Sunrun’s Wright said — “ and they should be able to compete on the market for the value they provide the grid.”
How can solar-battery systems compete for that value? That will be the subject of part two in our three-part series on California’s post-net-metering future.
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Jeff St. John is director of news and special projects at Canary Media.