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Solar + Storage = $avings!

03/28/17

  03:22:00 pm, by Jim Jenal - Founder & CEO   , 1002 words  
Categories: Solar Economics, Residential Solar, Energy Storage

Solar + Storage = $avings!

We have been waiting a long time for this moment, when we could finally say that we can offer a solar plus smart storage solution for our residential clients.  Well the wait is over, and if you act fast, there is even a sweet rebate available!  It is a complicated picture, so stick with us as we break this down.

Introducing the Enphase Energy AC Battery

Four Enphase Energy AC batteries installed

Four Enphase Energy AC Batteries

Regular readers of this blog know that we are big fans of Enphase Energy and have been installing their microinverters for years.  Given our history with the company, we were excited to be approached by Enphase to participate in their AC Battery “beta” install program, one of just a handful of selected installers in the U.S.  We selected the site of one of our largest residential projects for the beta, knowing that would give us great data to study over time (and you know how we love data!).  We really like the way the install turned out, nice and neat!

Let’s be clear about what this system is, and is not.  It is not a battery backup system.  It will not keep the lights on if the grid goes down.  It is an energy arbitrage system - it stores energy from your PV array for use later in the day when your rates are highest.  That means that this system isn’t for everyone; it is for folks who have a PV system (or want to install one!) and are subject to time-of-use (TOU) rates, which mostly means just some folks who are SCE customers.  (Important note to SCE customers - if you install solar after July 1st, you will be forced onto time-of-use rates.)

Each battery stores 1.2 kWh of energy and can discharge that energy at 280 Watts, giving a discharge time of 4.3 hours.  The beta install shown above is a total of 4.8 kWh and a discharge of 1.12 kW.

So how does this work? Consider SCE’s TOU rates - the cheapest energy (13.1¢/kWh) is from 10 p.m. to 8 a.m.  The next cheapest energy (16.6¢/kWh) is from 8 a.m. to 2 p.m., and 8 p.m. to 10 p.m.   The really expensive energy (a whopping 33.5¢/kWh!) is from 2 p.m. to 8 p.m. - precisely when most people are coming home from work or school, turning on the A/C, and lights, and the TV and on and on.  Ouch! 

But note that the peak time does not coincide well with the output from the PV array, meaning energy exported onto the grid during the day is worth half of what that same energy would be worth later in the day.

That problem is exactly what the Enphase AC Battery is designed to solve.  Each morning when the PV array “wakes up” it starts to power the local loads of the house.  As the system produces more power, excess power is routed to charging the batteries (instead of exporting onto the grid).  Once the batteries are fully charged, any excess power is then exported and the homeowner gets a net metering credit for that energy.  But now when we get to 2 p.m. and the energy rate kicks into high gear, any energy needs that cannot be met by the PV array is supplied by the energy stored in the batteries, thereby limiting the amount of really expensive energy that has to be purchased from the grid.

Here’s a recent day’s performance of the beta system (I told you the data was cool!):

Enphase AC Battery usage

The bright blue is energy from the array, the orange represents energy loads - pale orange is entirely offset, bright orange is drawn from the grid.  The green at the bottom shows the percentage of battery charge - sloping up between 8 a.m. and noon, constant until needed starting around 6 p.m., and then discharging to offset the household loads. 

At the top we see snapshot data from the 8-8:15 p.m. interval.  No power is available from the array (duh, it’s night!), but the house is consuming 533 Watt-hours of energy, with slightly more than half coming from the batteries.  (Hint - the system is entirely modular, so we could easily double the size of the system to completely cover those loads.)

Bottom line: if you are on a TOU rate, storage can really improve the value of your existing PV system.  (And because the Enphase storage system is “AC-coupled” it can be installed with any existing PV system!)

The SGIP Rebate Program

Which brings us to the Self Generation Incentive Program (SGIP) rebates.  Starting in April, rebate applications can be submitted for energy storage systems.  Much as the CSI rebate program had multiple steps over time, SGIP has five incentive level steps and how fast it steps down is tied to how large is the demand for rebates.  (We anticipate that the highest rebate level will be paid out almost immediately after the program formally opens on May 1.)  At this highest rebate level we would expect the rebate for each Enphase AC Battery to be roughly $430.

The competition for these rebates will be pretty fierce.  Fortunately, there is a dedicated carve-out of money for small residential storage systems, so all the money won’t be gobbled up by a few, super-large projects.  (Interestingly, priority will be given to folks living in what is known as the Western LA Basin Local Reliability Area - you can check to see if your zip code, which includes pretty much all of the Run on Sun service territory - is included by clicking here.)

The rebate is not limited to SCE customers; folks who are SoCal Gas customers (that means you, PWP and LADWP folks!) can also participate.

Go with the Pros!

Properly sizing a battery system to go with your solar array is a complicated process that requires technical savvy.  Dealing with the SGIP bureaucracy requires a sophisticated team that can deal with the program’s many twists and turns.  If adding storage - specifically the Enphase AC Battery - to your present or planned PV system sounds like a good idea, give us call, we’re ready to bring our expertise to bear to help you get this right!

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Comment from: sara  
5 stars
saraThis is great news! Even people with older systems that have string inverters can use these batteries.
03/30/17 @ 09:58
Jim Jenal is the Founder & CEO of Run on Sun, Pasadena's premier installer and integrator of top-of-the-line solar power installations.
Run on Sun also offers solar consulting services, working with consumers, utilities, and municipalities to help them make solar power affordable and reliable.

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