Sean, a further question. In the video you made the point that batteries are still expensive but costs are coming down. There was also a description of a grid tied, AC coupled system. If you are designing or purchasing a residential or small commercial system that may not require batteries now (perhaps you have net metering), but may require batteries in the near future, say a few years time when battery costs come down and net metering is removed, what should you specify so that your system is able to incorporate batteries without having to make costly change out of equipment,
There are a few different ways at looking at a solution to adding energy storage in the future to a PV system that you are installing now.
I would try and use an inverter that is made by a company that is likely to have a battery inverter in the future, which is probably a company that already has a battery solution. This way, we will be likely to have equipment that is more compatible. Companies can include SMA, Schneider, ABB and others.
Will you require the system to work when the grid is down? If your grid is stable and rarely goes down, it may not be worth the extra costs to have the PV system charge the batteries when the utility is down. In this case, you can get a battery system independent of your PV system. Your battery system will be a load when you want to hang on to some of your solar energy and it can send out electricity when you need to use more.
If you require your battery system to charge the batteries when the grid is down, it can be more complicated. You will want to plan having the solar and the backed up loads to go to a common subpanel (usually battery systems do not backup all of the loads).
There are many different ways that batteries can help and it will depend on the incentives, net-metering standards, time-of-use electricity rates, stability of the grid, generators on premises and utility rules.
Any grid-tied system can be converted to an ac-coupled battery backup system. It will take careful planning to determine your needs.
Here is a Schneider video with a battery solution that can work in many different ways depending on your needs:
I am sure in a few years, there will be something better and less expensive.