In Blog

Enphase AC Battery Reviewd

I’ve been so itching to write an Enphase battery review. The AC coupled Enphase battery seems to be gaining significant interest although its release date still three months away. It’s a revolutionary concept: a battery that can be fitted to any solar system – any inverter. Imagine that. Any solar system in Australia. You don’t have to have the fancy pants “battery ready” inverters that sales people are banging on about. No longer feed your power back to the grid for a miserable 6 cents. For about $2500, you can store it in a battery and use it at night. The battery revolution has begun, or has it?

When I review a product, it generally entails me sitting down with the manufacturer and compiling a list of pro’s and cons of the product. I shared lunch and a few beers with Florian from Enphase at the Hamilton hotel. We exchanged emails, sometimes vehemently. Finally, last Friday I had a tense Skype conversation with the bloke who is worth his weight in gold. This time, my apologies Florian, I’m not going to share the pros and cons. I’m just going to point out one glaring downfall of the Enphase AC Battery.

AC Coupled Definition

AC coupling simply means your battery will be charged from the output of the inverter. The battery is charged by using 240 volts AC. Because every inverter produces 240volts AC, any inverter can be linked to the an AC coupled battery such as the Enphase. More commonly, batteries are charged with the DC power direct from the solar panels. While there are many advantages to DC coupling, a downside is you will need to have a true battery ready inverter, and match it with selected batteries.

Enphase smoke and mirrors

After reading Grant’s comments below, I should point out that the logic I am using works for South East Qld. If however, you have a “time of use” tariff with low off-peak and high peak charges, then the battery could be charged a second time during off peak, and discharged twice during peak times. What follows is my logic with a flat tariff of around 25c/kWh.

So let’s do the maths the Enphase way. We’ll do as they suggest and get 3x 1.2kWh (1.1kW usable) batteries. This means you have 3.3kWh of usable storage. “But wait,” says Enphase, “because you can cycle the battery twice a day, effectively it is 6.6kWh of storage.” So now you have a battery solution that is theoretically a bit bigger than the Tesla or LG, and for around $7500 installed. And you have a better warranty. And, because it is AC coupled you can connect it to any solar inverter. We’re on a win, win, win … right?

Enphase AC Battery smoke

Bugger, there is a catch. The 1.2kWh Enphase batteries charge and discharges at 270W each. Three batteries will charge and discharge at 810W. To do two cycles of these three batteries, you need to have.

  • 800w of excess power between 6 am and 10am to perform a charge cycle.
  • 800w of deficiency between 10 am and 2 pm to perform a discharge cycle
  • 800w of excess power between 2 pm and 6 pm to perform a charge cycle.
  • a piddly little 3.3kWh of discharge at night.

This is not even remotely realistic.

It obviously depends on your load. If your solar production curve is frequently intersecting you consumption curve, you may be able to get 1.5 cycles. This type of usage pattern may happen occasionally if you are at home during the day. But really, this is not the problem we are trying to solve with batteries.

Look in the mirror

My logic is:

  • If you want to store power you want to first oversize your solar system. Oversizing your solar system in most cases means installing 6.5kW of solar on your roof. Oversizing is cost effective.
  • After you oversize your solar system, the next most cost effective measure is to load shift. This means using the inverters intelligence to turn on or off your hot water or your pool when you are exporting power. Load shifting will always be more cost effective than storage. Enphase does not offer an interactive load shift solution like the Fronius smart meter and relays.
  • Once we have oversized your solar and we have implemented load shifting, we then look at excess production and excess demand. Batteries are there to buffer, to soak in excess solar production and to deliver when demand exceeds solar supply – generally at night.

The piddly little 810w of power absorption that Enphase offers does not fit what a 6500w solar system on a standard home requires.

There are so many factors that Enphase want to discuss. The safe LiFePO4 chemistry, AC Coupling vs. DC coupling,  scalability, safety, and warranties. But if it does not work, it does not work. It does not work. Enphase, the concept is there. I love the flexibility of AC coupling. In time Enphase (or their competitor) will release an AC coupled battery that will meet the aggressive charge and discharge market demands.

Sonnenbatterie may be one example. The AC coupled battery will be available before the end of Q2 2016. I’ve posted a review on sonnenBatterie since I wrote this post here.

I’ve been wrong before

Most recently I was wrong when I bagged out the Redback inverter prematurely. I’m more than happy to take comments from Enphase or from my competitors that back the Enphase battery for what I see as no more than opportunistic reasons. Leave your comments below!


13 Comments on Enphase AC Battery Review

Mark C said : administrator Report 9 months ago

Thanks for sharing your experience. A bottleneck is exactly what it is!

Marf said : Guest Report 12 months ago

Hi Mark We were early adopters of the enphase technology micro inverters three years ago and installed two enphase batteries back in December 2016. We then over the last year followed the steps that you have suggested oversizing the system, shifting loads and then batteries for buffering. The slow charge and discharge is exactly what we are struggling with, we are so frustrated that we are exporting between 4 to 8 kilowatts back to the grid, and the batteries are not even charging fully on most days!! We like all the information the monitoring system gives us, but are frustrated by the bottle neck from the batteries! In sum batteries are a beautiful, but inefficient and expensive object

  • 2042
Mark C said : administrator Report one year ago

Hi Heather, That sounds frustrating. We can't charge batteries from the grid in Qld, I'm not really sure which parts of Australia can. It would be all down to your own utility, and- I guess a competent electrician!

Heather davidson said : Guest Report one year ago

Trying to get installers in the uk to set a dual cycle is hard. I got 2x1.2 batteries installed in june. They WILL NOT set batteries to charge off peak ie 12... 7am. That way they will discharge when peak starts and charge during the day and discharge in the evening. You say this can be done but in pratice noone does it. Enphase state it is how they are designed to be used. Why installers just want your money and run away from setting up to best efficiency.

  • Fk4 1dg
John said : Guest Report 2 years ago

Whatever the pros and cons of the technical arguments, it fall down on value. I have been quoted $10000 for three 1.2/1.1 cells plus controller. This takes you most of the way to a14 kWh Powerwall 2 and new inverter! Why would you even consider the Enphase? It escapes me.

  • 2640
Mark C said : administrator Report 2 years ago

Hi Frederick, I'm not sure of the importance of your point. LG, Tesla, Fronius, GCL with their matching inverters all discharge and charge with a small amount of power when generated. However, it would partly be up to the inverter as to how precise that is. I know the LG sungrow setup doesn't work to an accuracy of 1w. Is your point the precision of the Enphase? If so that's interesting but I wouldn't have thought it was a significant consideration. And I would doubt the 1w accuracy because from memory Enphase uses a CT, not a whole current meter. Mark Cavanagh

Frederick Poole said : Guest Report 2 years ago

You make one error in your "review" which is kinda important.....the AC battery has a MAX charge/discharge rate of 270W....MAX. So as soon as you have 1W of power spare for charging they start, and vice versa for discharge. Like i said, kinda an important point!

  • 9930
Plu42jiKoyh said : administrator Report 2 years ago

Thanks for your opinion - but I beg to differ. The problem with the enphase battery is in my opinion the charge and discharge rate is so low it's not worth actually hanging on my wall and testing. The specs make me not want to waste money testing it. It will probably work really well for what it is designed to do. But it's not designed to work very hard. I'll guess that you have sold or installed Enphase batteries, so I'd be keen to engage in discussion. What is it about my opinion that you don't like? It's a little different than fake news.

Ummm Facts? said : Guest Report 2 years ago

This 'review' is prior to product launch, so it is a 'review' of the specs, not any real world testing or actual data analysis. It is essentially an opinion piece on an unreleased about a follow-up once you get to see the production product in action? This is almost close to fake news we have been seeing more and more of in social media.

  • 94602
Taldan16 said : Guest Report 3 years ago

Grant, I would like to challenge your points on two cycles per day even under time-of-use schemes when it comes to real scenarios with the Enphase AC battery. I quote your statement: "Cycle 1 - the battery charges up before sunrise using off peak (or “shoulder”) electricity from the grid and discharges this into the load in the period when the power from the PV array is not yet sufficient to fully meet the load. Cycle 2 - the battery charges up during the daytime period when the PV array power does exceed the load and then discharges into the load as soon as the sun goes down." This is simply unrealistic scenario for the vast majority of solar+storage customers. The reason (again) 4 hours charge/discharge rate. In order to take advantage of this Cycle 1, the load should exceed the PV production for 4 hours in the morning and this should co-exist with the peak tariff that will last for those 4 hours. Usually people leave their house in the morning and the consumption drops. At the same time the PV starts producing energy and you get an excess power that you would like to store, rather than consume energy from your battery. In the best case, I can see 30min - 1hr of "Cycle 1" in the morning (under best possible conditions, with really high arbitrage between peak and "shoulder" rates). And when this happens, I would want to have maximum power from my battery, not the battery that at max can be discharged in 4 hours. So, as Marc said in his blog, two cycles per day in real life is "even not remotely possible" (including the time of use scenario). I wish customers would be able to recognize when the reality meets the marketing pitch. All the best.

Plu42jiKoyh said : administrator Report 3 years ago

Thanks for your comments Grant. I've seen on recent forums where the Enphase would work on time of use tariffs in other states where you can charge the battery at night. I should be more careful to point out that I am writing for my target audience South-East Qld. I know that with twisting figures and the entry level price, the Enphase battery is being sold as a viable storage solution in Queensland - but currently it is not. I will agree after installing thousands of Enphase Micro's without a single failure, Enphase make a solid product.

Grant Behrendorff said : Guest Report 3 years ago

As usual Mark, an interesting and insightful blog. There are couple of points I would make though to challenge your conclusion. Firstly, the Enphase AC Battery is not intended to be cycled twice a day using solar power as you outlined. To do so would, I agree, not be “even remotely realistic”. The Enphase product documentation and promotional material do show it as being designed to cycle twice a day but it’s based on a completely different assumption: Cycle 1 - the battery charges up before sunrise using off peak (or “shoulder”) electricity from the grid and discharges this into the load in the period when the power from the PV array is not yet sufficient to fully meet the load. Cycle 2 - the battery charges up during the daytime period when the PV array power does exceed the load and then discharges into the load as soon as the sun goes down. Although the economics of all home energy storage systems are currently marginal at best, cycling the Enphase AC Battery in the way it is intended would provide a better economic return than most, if not all competing products currently in the market place in Australia. Of course this is dependant on the availability of a suitable electricity tariff to enable cost effective charging of the battery in the early morning. Although I wouldn’t say these tariffs are ‘common’, there are already several electricity retailers offering suitable tariffs and we can expect to see many more residential time-of-use tariffs being introduced in the coming years. The Enphase AC battery is one of very few batteries available that are capable of taking advantage of these tariffs as they emerge. You are correct to point out that the AC Battery is designed to take approximately 4 hours to charge and 4 hours to discharge. All energy storage systems have maximum charge/discharge rates and this rate is often a trade off against battery longevity. Just because a DC battery system has a 2 or 3 or 4 kW inverter/charger doesn’t mean that the battery can (or should) be charged or discharged at that rate and doing so often affects the life of the battery and therefore the return on investment. There is always a trade off. Enphase have literally spent tens of millions of dollars developing the AC Battery and the Enphase home energy solution ecosystem. I am sure you would agree that the quality of the existing Enphase products and the significant market share they enjoy all around the world would indicate that they do understand a thing or two about energy generation and management. I understand that the AC battery has been modelled in hundreds of different load scenarios using real data from systems located all around the world including right here in Queensland, and already undergone thousands of hours operating under various load and test conditions. It’s possible that the enormous about of money spent on development and the expertise of hundreds of engineers who have worked on the project for several years have been misguided and will result in a product that doesn’t work, (I too "have been wrong before"!) but with four months to go before the first production units hit our shores and with none of us ever having laid our hands on one, let alone played with one to see how it performs, I think it is a bit too early to conclude that the AC Battery "does not work".

Solar owner said : Guest Report 3 years ago

I think smoke and mirrors is too strong a statement. If you look at the web available material (interviews, articles and such) I think what Enphase is really doing is positioning themselves early in what is probably going to be a big market. They've said on many occasions that the cost of the chemistry is going to plummet, and guess what? They'll be there with the hard part, which is the integrated Cloud distributed system. Just an interested bystander. I'll pick up a few batteries when they release to play with, and watch closely the cost of the chemistry. Meanwhile system owners and installers can prepare themselves for adding storage. A Battery Is Just A Battery and Other Myths About Energy Storage.

Leave a Reply

Your email address will not be published. Required fields are marked