Category: "Energy Storage"


  06:41:00 am, by Jim Jenal - Founder & CEO   , 949 words  
Categories: All About Solar Power, Residential Solar, Energy Storage

New Rule in SCE Territory Makes Solar + Storage More Valuable

We just learned from our friends at Energy Toolbase that Southern California Edison has just changed a rule about how solar PV systems with Energy Storage can operate, and the result - amazingly enough - results in greater savings for our clients!  Imagine that?!?  Here’s our take…

It used to be in SCE territory that when you added a storage system to your PV array, you could not export energy from the storage system to the grid and receive net metering credit.  That meant that when the storage system was discharging, it could not exceed what the home’s loads were demanding.  If your usage in the evening was low, or say you were out of town, your fully charged battery could not discharge at all - a poor utilization of that expensive storage system.

But now SCE - along with the other IOU’s, PG&E and SDG&E - have changed their rules to allow storage systems to discharge back to the grid and receive full net metering credit for that energy, as long as the storage system is solely charged by the PV array.  When you combine that rule change with electricity rates that favor storage, such as SCE’s TOU-D-Prime rate, the change in the rule can account for significant savings.

To get a handle on how big a change this will be, we went back to the data that we have for a client who we will be installing a small PV array and a 10 kWh Ensemble storage system soon.  (All of our data analysis and visualizations you see here were done using Energy Toolbase, simply the best presentation tool on the market.)

Solar PV & Storage - No Net Metering Discharge

Our client with the small, 4.6 kW, PV system and 10 kWh Ensemble storage system has a system payback of 11.4 years.  (Larger systems would have a faster payback.)  For this analysis, we imported his SCE interval usage data (provided by UtilityAPI) into Energy Toolbase.  ET then takes the performance output from the PV system, the charge and discharge parameters of the storage system, and overlays that on the existing usage - doing that calculation over every fifteen minute interval for a year.

The graph below shows one day, July 8th, as a representative sample.  Let’s break this down:

Solar PV + Storage - no net metering discharge

There’s a lot going on in this image (click on it for a larger version).  The dark gray is the historical usage demand based on the SCE data.  The value is shown at the top as “Current Demand” and at the moment we have focused on - July 8 at 4:15 p.m. - the historical demand was 1.94 kW. 

The green curve shows the modeled PV array output, using the specific parameters for this site - azimuth, tilt, shading, historical weather, specific equipment being used - as determined by NREL’s PVWatts tool (version 5).  Right now it is at 1.17 kW. 

The red line shows the percentage state of charge for the storage system, at this moment it is 83%.  Net Demand is what is being imported (positive number) or exported (negative number) to the grid.  Finally, Battery Power is how much power is being pulled from the storage system which at this moment is 1.94 kW.  At the bottom is the cost parameters for this rate schedule.  Under the pre-solar Domestic rate (which is a tiered rate) the cost of energy is 18.7 cents/kWh, whereas under the new rate structure it is more than twice that at 38.3 cents during the peak, 4-9 p.m. period.

 So… earlier in the day, as the output from the PV increases, and energy charges are cheap, the solar charges the battery for use later when the rates are high. As we cross over into the peak rate period at 4:00, the storage system begins to discharge and its output is exactly the same as the demand, meaning that all of the power from the PV system can be exported to the grid. 

But note that the battery power is only 1.94 kW, even though its continuous peak output is roughly twice that, 3.84 kW.  Under the old rules though, the storage system cannot output more than that, since it is barred from exporting to the grid.  As a result, when the peak rate period ends at 9:00 p.m. the storage system shuts off, even though it is still partially charged (nearly 40% capacity remains in this example).

That’s leaving money on the table!

Solar PV & Storage - Net Metering Discharge Allowed

Consider the same day, only now we can export the full output of the storage system as desired to maximize our time-of-use arbitrage.

Solar PV + Storage - no net metering discharge

Everything is essentially the same until we get to 4:00 p.m. and then things get very different!  Look at the difference in the output from the battery system, it is now putting out it’s maximum sustained power of 3.84 kW, resulting in more than 3 kW being exported during the peak price period

More importantly from an arbitrage perspective, the storage system is completely cycled.  Meaning that we have gotten full utilization from our storage system investment.  

What does that mean overall economically?  Payback is reduced from 11.4 to 10.7 years, a 6.1% improvement.  Gee, thanks, SCE!

So why are they doing this?  Simple: grid support. Having storage systems maximizing their output during the peak demand period (remember the Duck Curve?) helps the utility to manage its load, and reduce the need for expensive peaker capacity. Everybody benefits: our client (with faster payback), the utility (with better grid load management), and even non-solar/storage rate payers (as they don’t have to pay for that additional production capacity.  Win, win, win!

Of course, these economic benefits don’t really apply to a tiered rate structure, such as is used for residential rates in PWP territory.  But if you are in SCE territory, adding smart storage, like the Enphase Ensemble system, just became a lot more lucrative.



  05:45:00 am, by Jim Jenal - Founder & CEO   , 1640 words  
Categories: All About Solar Power, Residential Solar, Energy Storage

Hands-On with Ensemble - My Trip to Enphase!

I just returned from two days of hands-on training with the new Ensemble Storage System from Enphase Energy at their HQ in Fremont, California.  Here’s my take…

Ok, to say that I have been somewhat obsessed over the Enphase IQ8 and its incarnation in the Ensemble Storage System over the last year and a half would be an understatement, having written about it here, here, here, here and here!  I’ve attended webinars and conference sessions where Ensemble was discussed and the technology explained.  But like any good installer, what I really wanted to do was get my hands on these devices, wire them up, and get a real feel for what it takes to put these on a client’s wall.  This week I got my chance!

Ensemble lab

Ensemble Family Photo: Enpower, Encharge 10, Encharge 3, IQ Envoy Combiner.
(Click for larger image.)

Here is one view from the lab at Fremont.  On the far left is a main service panel and meter. To its right is the Enpower Smart Switch which acts as a Microgrid Interconnect Device (or MID). Next is the Encharge 10, alongside its smaller sibling, the Encharge 3. 

(As this image suggests, Encharge 10 and Encharge 3 can be combined as desired to achieve the combination of energy storage and power output required.) 

Next is the IQ Envoy Combiner (not new, although it now comes with a cellular modem standard).

Finally, there is the simulated array made up of IQ6’s and IQ7’s (both regular and Plus versions).  Out of the field of the picture is a PV array simulator that powers the microinverters.

Oh, and no demo would be complete without some loads, including a light, a microwave, and an electric stove - all of which were powered by this system with the grid disconnected.  (Some people have asked how fast was the switchover - so fast that the light doesn’t blink and the clock on the microwave did not reset.)

Over the course of the two days we spent a lot of time in the classroom - headed by Peter Lum, trainer extaordinaire - focusing on the nitty gritty.  How do you size an Ensemble system, how do you mount these things, how do you wire them up, how do you comply with the electrical code?

Our lab time on the first day was a demo of the system on the wall.  The second day, we were actually mounting these to the wall and wiring them up.

Getting Our Hands Dirty

I’ve already written a lot about the specs of these devices, so I won’t repeat that here.  The point of this post is to discuss the actual installation process.

Enpower and Encharge10

Enpower with deadfront removed alongside Encharge 10.
(Click for larger image.)

On the left is the Enpower with its deadfront removed, alongside the Encharge 10 with its cover removed.  (The whitle, L-shaped pieces on top of the Encharge 10 cover are the screw down covers for the Encharge’s wiring compartment.)

Encharge 10

Let’s start with the Encharge 10 - as the photo makes clear, Encharge 10 is actually three Encharge 3’s mounted on a common mounting bracket.  Each Encharge 3 includes four IQ8 microinverters, and they are individually replaceable, so should one ever fail, the others continue to operate and the monitoring will advise the installer of which unit has failed.  All the field technician needs to do is remove the cover, disconnect the failed microinverter, plug in the replacement, and put the cover back on. Moreover, because the micros are on a common bus inside the Encharge 3, if one should happen to fail, you still have 75% of your total power, but 100% of your stored energy!

An Encharge 10 constitutes a 20 Amp branch circuit, and up to two Encharge 10’s can be wired together in series (maximum wire size is #8).  If a larger storage system is required, then the Encharge units need to be landed in a dedicated subpanel.  (The Enpower is rated for up to 80 Amps of storage.)

To the left of the IQ8s is the battery management unit and the battery disconnect switch.  (Not really visible in this picture is a status LED that shows whether the battery is on or not, whether it is idle or charging, and the relative state of charge as it shifts from blue (discharged) to green (charged).

The finned area is the actual LFP batteries themselves.  All cooling is passive, no fans are involved.  The unit needs to be mounted a minimum of one foot from the ground, and if you have more than one row, at least six inches (vertically) between rows.

The mounting bracket is secured to the wall with sufficient hardware and into sufficient structure to support the total weight of 346 pounds.  (Enphase will be releasing a white paper on best mounting practices - a must read to be sure!)  Each individual Encharge 3 is then lifted onto the bracket.  Given that these are over 100 pounds, this is a two-person lift to be sure!  My colleague Greg and I struggled a bit with the lift, mostly because I wasn’t really pulling my weight - so to speak.  (My value add isn’t really in lift strength!)  But the younger guys that were in the training with us managed the task with ease - ah youth!

Wiring compartment of Enphase Encharge 3

Encharge wiring compartment.
(Click for larger image.)

The Encharge 3’s are then daisy-chained together in a wiring compartment at the top of the units, as you can see in the picture on the left.  Each terminal block can hold two wires, one coming in, one going out.  The last unit just has the incoming connection and no other termination is required.

Note the black piece connecting to the two units.  That is a plastic, snap in conduit section that is added after the units are mounted.  The last unit in the chain has a rubber plug in that opening to keep the wiring compartment watertight. 

(Note, the section with the microinverters is not watertight as the IQ8’s are NEMA 6x, which means that they can - and are tested to prove it - operate under water!)

Once the wiring between the Encharge units is complete, the unit closest to the Enpower is then wired to it, and then the tops can be screwed on, and the cover added.


Which brings us to the Enpower - which is both a MID and an interconnection center.  Note, however, that Enpower is not a general purpose panelboard, but rather, a specially listed UL device and as such, the 120% rule does not apply.  As a result, the Enpower will accommodate up to 80 Amps of PV input (i.e., a fully populated IQ Combiner) and 80 Amps of storage input (i.e., four Encharge 10’s.)

In the picture above, the input from the meter (if serving as a whole-home backup system) or the the main service panel (in a partial-home backup) comes in on the right hand side.  In the picture there is an Eaton main service, bolt-down breaker installed.  If this were intended for a partial-home backup with a breaker in the main service panel, the Eaton breaker could be omitted and the input conductors would land on the existing lugs.

Directly above that main breaker is the isolation relay, which trips when the grid fails and isolates the system for creating a microgrid.  Above and to the center is the neutral forming transformer that allows the system to power 120 VAC loads.  Below that on the left is the common bus that holds (going counterclockwise from the top left) the breaker for the PV, the breaker for Encharge, a breaker for a generator (but not yet), and the breaker for the neutral forming transformer.  

You can see the conductors for all of those connections pre-wired in the photo, waiting to be attached to the appropriately sized breaker.  The actual connections for both the PV and Encharge are made on lugs at the very bottom.

The output to the loads is at the base of the common bus where an appropriate Eaton breaker is added.  Fun fact - the Eaton service rated breakers actually swap L1 and L2 from one side of the breaker to the other!  This means that installers need to pay attention to their phasing so that the consumption and production CTs are reading the proper values - a topic we discussed in some detail in the classroom, and then verified in the lab - damn, isn’t hands-on training the best!

The Enpower switch, the Encharge units, and the IQ Envoy Combiner all communicate directly via Zigbee.  In fact, each unit has two radios, one at 2.4 GHz and the other at 900 MHz and the units switch automatically between channels and frequencies as necessary to provide the clearest signal.  Moreover, if the Combiner box is remote from the Enpower but closer to Encharge, the Encharge unit (or vice versa) can serve as a repeater to get signals to the other devices.  Pretty clever.

Providing Feedback…

Of course, there are two purposes to a training like this during a beta period: to get the initial installers up to speed with the product, and for the installers to provide Enphase with feedback.  Along the way we discovered a diagram that was wrong (nice pickup, Greg!), and a couple of places where esthetics got in the way of utility.  Those are easy things to correct, and Enphase’s CEO himself came into our classroom to hear our feedback directly!  That is a level of dedication to hearing what the long tail has to say that just isn’t happening with other solar companies.

Finally, a point of personal privilege: some years ago we did a video about our installation at Westridge School for Girls here in Pasadena (you can find it here.)  Well what do you know but that video is part of a loop that is playing in the Enphase lobby!  One of the engineers actually came up to me and exclaimed, “You’re the guy in the video!"  Fun way to end our two days at Enphase HQ. 

Bring on the Beta!


  03:38:00 am, by Jim Jenal - Founder & CEO   , 867 words  
Categories: Residential Solar, Energy Storage

Let's Talk Ensemble!

[Editor’s Note: Today is Veterans’ Day, so a shoutout to our Vets: Victoria and Greg,
and to all the Vets out there - thank you for your service to our country.]

The Enphase Ensemble system is almost here, so let’s start talking about how this is going to work for existing and potential clients.

What is Ensemble?

Ensemble is the name of the new Enphase storage and control system.  It consists of the Enpower smart switch, some amount of Encharge battery systems (depending on your needs),  and an IQ Envoy to handle communications.  The system is capable of supporting “whole home” backup, although for most clients a “partial home” system will make more sense.

Enpower smart switch    Enpower 10 kWh storage system 

 Enpower Smart Switch

19.7″ x 36″ x 9.7″

80 lbs.


 Encharge 10 kWh Storage System

42.12″ x 26.14″ x 12.56″

346 lbs.

The Enpower smart switch contains an automatic transfer switch - or a Microgrid Interconnect Device, to use the language of the NEC (to isolate from the grid when there is a grid failure) - rated at 200 amps, and a neutral forming transformer to allow for 120/240 VAC operation.

The Encharge batteries come in two sizes: a 3.3 kWh battery and a 10 kWh battery (which is actually three of the 3.3 kWh batteries mounted behind a common cover).  Inside the 3.3 kWh unit are four IQ8 microinverters, and thus 12 as part of the 10 kWh unit.  The 10 kWh unit, which is going to be the minimum size that you will want, has a continuous output power of 3.84 kW, with a peak out of 5.7 kW for ten seconds - enough to allow for inrush current from motors, for example.

Both units have a NEMA 3R rating so they can be installed outdoors (though you will want them out of direct sunlight if possible), and come with a 10-year warranty.

How Will it Fit with My Existing System?

First, you need to have IQ microinverters.  At least as of the initial rollout of this system, the older microinverters are not supported.  That means that the M and S-series of microinverters have to be replaced to IQ-series microinverters to work with Ensemble.  (I do not know if this will change in the future, but it is the guidance that we are getting at this time.)  It is possible that there will be some sort of replacement program (like Enphase did with the legacy M-190 customers), but I have not gotten any word about such a plan yet.

Second, you need a rough parity between the output power of the solar array and the output power of the Encharge batteries.  That means that if you have a single, 10 kWh Encharge battery system, the rated output power of the installed microinverters on the roof, has to be at or below 5.7 kW.  Here’s what that means for the IQ microinverters that have been installed in the past three years:

IQ micros per Encharge capacity

As the systems that we have been installing have all been IQ6+ or IQ7+, you can see that with a 10 kWh Encharge system, you are limited to 19 panels - a 6.365 kW system when paired with LG 335’s.

How can I Plan to Make Ensemble Work Best for Me?

Making this work requires some planning and modifications, and not every existing system will be a good candidate for this.  As we have noted in earlier posts about Ensemble, most folks in Southern California have what is called a combination service panel where the meter unit and the distribution unit (where the breakers are) are in the same, physical device.  Without replacing the service panel, you are left with a configuration that will looks something like this:

 Typical Ensemble System

Ensemble Wiring Layout - click for larger.

That is your PV system in the top left powered by IQ microinverters.  Those land on an IQ Combiner (which Run on Sun has been using since the IQ microinverters were rolled out).  On the far right is the grid, feeding your meter and the service panel.  (In an existing system, the output from the IQ Combiner goes to a disconnect switch and then to a breaker (or a lug) in the service panel.)

To add Ensemble, you need to connect the Enpower switch to the service panel via an appropriately sized breaker.  You also need to create an emergency load subpanel, with the critical loads that you want to operate during an emergency.  (This takes a good deal of thought - you will need to know the power requirements of the devices you are looking to operate during the outage and size the system accordingly.)  Everything then flows through the Enpower switch (including the possibility of a backup generator, though that will not be immediately supported).

We do not yet know what the utilities or local AHJs will say about this.  Presumably the utilities still want a lockable disconnect switch on the output from the Combiner, but will they also want one on the output of the Encharge battery system? The Encharge system allows for two, 10 kWh units to be “daisy-chained” together; for larger storage system a storage subpanel is required.  Also required is consumption monitoring, which may not be possible on some service panels (due to space constraints) without rewiring the entire panel - ugh.

So… this is going to be a great product, but it is neither a cheap nor simple process.  Interested?  Let’s get started!


  07:17:00 pm, by Jim Jenal - Founder & CEO   , 134 words  
Categories: All About Solar Power, Residential Solar, Energy Storage

Ensemble Rollout Coming into Focus

On the heels of their video release last month, the folks at Enphase have now published an FAQ page on the entire Ensemble system.  Here are some highlights…

Perhaps the most exciting item is that they are expecting deliveries around Christmas time – what a great gift!  That said, I’m sure quantities are going to be limited at least initially. To that point, however, it looks like there will be a “pre-order” option - though the FAQ page is silent on details or pricing.

The most disappointing answer is that the system will not be compatible with S and M series microinverters, although they are planning an upgrade path, similar to the “Early Adopters” program that they had earlier this year.

Happy to hear your feedback - obviously we are following developments here closely, watch this space.


  08:20:00 pm, by Jim Jenal - Founder & CEO   , 211 words  
Categories: All About Solar Power, Residential Solar, Energy Storage

Enphase Releases Video on IQ8 and Ensemble

Our friends over at Enphase have posted a video to YouTube explaining in non-technical terms what the IQ8 will do for solar consumers, both in the developing world, and here at home.  Here’s the video and some quick thoughts about it.

To quote the video, “Isn’t it cool?"  Well yes, as we’ve been saying for quite some time here, this is waaaay cool.  But here are some other takeaways from the video:

  • Strong endorsement for interoperability with the IQ6’s and IQ7’s that we have been installing for the past year and a half.  But no word about how this will work with earlier versions.
  • The Enpower switch - which is needed to legally isolate you from the grid - is pictured, but still no details.
  • A hint at pricing would be nice!

As far as I’m aware, this is the first, general-public-facing details about the IQ8 and Ensemble that Enphase has released.  It went live on May 28, and three days later is sitting on just under 15,000 views, with 154 up-votes to 6 down-votes.  (What is there to down vote?  Gee, SEDG, troll much?)

This will be very cool technology for our clients, but it will truly be life-changing for folks in the developing world or any place where the grid is unreliable.

Watch this space.

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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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