Battery Storage System

[BertHamm]

I have a 12kw solaredge system on my home. It was installed July 2017. At present my utiloity buys back the surplus power at the same rate I pay for it. After 10 years of operation, the utility will buy back the power at a discounted rate. Approximately half what they pay now.

I'm considering adding a storage battery system in a few years but know very little about it.

How much battery storage would I need? Exactly when does the battery kick in? Is it every time I draw from the grid, at programed times? Is the transfer from grid to battery and the reverse seamless? Does the power go off monetarily, flicker?
Appreciate any help here......Bert H.

[azdave]

Unless you have high energy rates and a TOU plan that incentivizes you store up power in the batteries during cheap periods to pull back out during expensive periods, I would not even bother. Also consider that like in California, your POCO could change the rules at any time and leave you with a much longer ROI than expected. There is a whole lot more to consider before you add storage capacity but this is one thing I would look at first.

I would never install batteries myself. Our power is very reliable. It's maybe been out 10 minutes in total in over 15 years. In the last 3 years, not so much as a blink in dropped power. We also are not required to be on a TOU plan (nor would that save us money if we changed). Our energy costs the same all day long and banked power is used at a 1:1 rate. Our excess power bank is paid out once a year at wholesale rates and we usually get an annual $250-$400 account credit from that.

Keep doing your research and don't jump into it until you have a clear understanding. In my case, any large solar investments made today would probably not reach the ROI point before I leave this earth so why spend the money and complicate my life with more things to maintain and worry about?

[GoingElectric]

Unless you are in Texas, what AzDave wrote is solid. Depends completely on your utility.

[BertHamm]

I hadn't thought about the rate of return. As it is, the salesman that sold me the system said I would pay for the system in 15 years. Even after 7 years, it's obvious that ain't gonna happen. I live in Tenn. All the utilities in East Tennessee get their power from TVA. TVA is one of the least expensive utilities. Approximately 10 cents a KwHr I've gotta rethink the battery storage system. Appreciate the replies.

[Rade]

I had 18kW of battery storage installed as part of our solar architecture. The batteries made up almost half of the overall cost of the project. I live in an area of Rhode Island that is not prone to power bad outages. When we get them, the outages last no more than several hours. We did have one outage that lasted 36 hours, but that was one instance out of the 20 years living here, and came during a particularly brutal blizzard. 18kW of battery power is sufficient to keep our home functional. We had several critical circuits moved to a sub-panel that is tied through our inverter; refrigerators, freezer, mini-split for heat, a couple of central outlets.

The other advantage to the batteries is that, during high summer, we can place the inverter into what they call "Self Supply" mode, where the house will use the solar power until the sun sets, then use battery power until the batteries bottom out (20% remaining reserve power) before switching to pulling power from the grid. During that time this season, the days were long enough that the sun would be rising and firing up the panels before the batteries were depleted. We went one whole week without any draw from the grid. The downside to that was that we also did not generate a lot of credits for use in the depths of Winter.

If you live in an area of the country where you don't have long, winter nights or need to heat the house, a battery option might pay for itself in 8-10 years.

We had a professional electrician install our system.