Solar PV and Battery Storage

Howdy all,

Leaning towards spending some cash on a 4kW PV array with battery storage. I understand the principal of having a battery to use more of the generated power and rely less on the grid, but I’m not finding the right info on the mechanics of it. Everything is either too technical and aimed at installers or it’s too simplistic and explains the basic idea.

I’m looking for stuff like how to actually use it, what can and can’t be controlled (inverters, batteries) etc. Thinking such as can I toggle battery power on and off, disable grid power, use the battery only as a UPS type setup etc?

Then the obvious question and the reason for posting here - how to integrate with HA and some recommended brands?


Well, vast question(s)… and you will have probably more info than you need in my answer…

First, I think you need to think what functionalities you really need for your PV array because some that you have listed are not “created” by the usage of HA or any other domotic system but by the functionalities of the equipments you have bought… example: you want to use the battery as a UPS (during power outage for example)… Inverters are not all able to work without the grid… So if you want that functionality, you will have to buy an inverter allowing to work on the grid of course but also off grid (and generally it is of course more expensive)…

Regarding the mecanic of the battery, the inverter is doing the job automatically… No need to worry, but you maybe have some parameters to configure in the inverters during installation (I do not have physical batteries as this is too expensive for the time being in my country versus the benefits the batteries can bring… this can change in the near future based on the evolution of the price by Kwh…) This remark just to say that looking at PV is not only a question of technical functionalities or control but also a question of how fast your investment will be paid (and it is for me the crucial question…because the return on investments can drastically vary from one solution to the other: the last systems I implemented had a range of ROI from 4 to 13 years ! based on the different technical solutions I was looking for: with batteries, without batteries, central inverters or micro inverters, how much solar energy will I use directly ? 30% per year or 80% per year ? the ROI is not the same at all ! …).

Now regarding controlling those installations: I have two PV installations in two different locations and I do not control them, I just record what they produce that’s it (as I said I do not have physical batteries, I will come back on this later)… but I do control/manage the consumption side: I reduced power consumption by replacing high energy equipments by “greener” material, I try to use during the day a maximum of the energy produced by the solar panels (starting boilers or charging my EV), cutting unused equipments (like air conditionners or heating systems… if not used, they consume energy), that’s where HA is very useful by increasing the percentage of the solar energy you consume directly (self-consumption)… but one case is not the other…

Now regarding batteries, as I mentionned I do not use physical ones (because their lifetime is pretty “short”: 10 to 15 years and they are expensive). Nevertheless in one location, I use virtual batteries (because provided by some energy provider in that country)… Principle: I store the excess of energy produced into a virtual battery (in fact the energy is sent back to the grid) and when you consume more than you produce, you reuse that energy (that you do not pay as you produced it) but you have to pay the tax and the transport which is for me a more cost effective solution than buying physical batteries…

My two installations:

  • Installation 1: two inverters SMA (warranty 10 years) with 22 panels for a 5.7 Kwc installation - already 10 years old… (one inverter was already replaced under warranty by a GroWatt)
  • Installation 2: 6 micro inverters (DS3 APsystems - 880VA - warranty 20 years) with 12 panels 410 Wc (Hyundai - warranty 25 years) for a total of 4.92 Kwc (installed this year with Virtual batteries).

PS: check also the warranty for your equipments, it can widely vary from one brand to the other or from one solution to the other (inverters vs micro-inverters)…

As I mentionned, probably too much information… but don’t hesitate to ask question …

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Thanks for the long and comprehensive response.

Priorities for me:

  • Reduction in electric bill
  • Keep my server/CCTV active during power cut/blackout.

I’ve been quoted by a local installer for a 4kW array with SolaX 5.8kWh battery pack but I don’t understand how to use it i.e. how much control will I get over when the battery is used, to what extent can it be integrated to HA etc?

Virtual batteries - interesting concept though I don’t believe this is possible in the UK yet.


Regarding SolaX, you have a core integration for this inverter in HA (see the link below)… but as I said, I think this is only providing entities about the status of the power produced, used, battery level and so on… If you want to influence the way your system is distributing/using the energy, you have to have control on the equipments consuming this energy… For example: you should have shelly’s or connected plugs on the equipment you don’t want up during a power shutdown to give the maximum power to your server/CCTV system, as the SolaX will restore the energy from the batteries to the equipments connected during a power shutdown…

But maybe someone having a SolaX could tell you more about the way to interact with that inverter as it seems there ar more than one mode allowed: self-use, force time use, feed in priority… etc… If you are moving this way, maybe create a new topic just related to SolaX and ask some feedback about how to interact with it…

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I’ve just done some more reading and I’m sort of starting to understand the principals now (I was looking for how they actually work to try and help in selecting products etc).

Basically a PV system feeds straight back (via its inverter(s)) into the consumer unit on an MCB. The generated power has nowhere to go if it isn’t used, so it goes back to the grid. A generation meter measures generated power. The difference between the generated power and the reading on the grid meter is the amount of power fed back into the grid.

Inverters detect if there’s no grid supply and isolate their own supply as a safety feature, so the electrician doesn’t get a nasty shock when turning off the mains.

So, If I’m generating 2kW and I put on the 3kW kettle, the locally generated power will all be consumed and so the grid will supply the shortfall (1kW).

If a battery is added on the DC side of the inverter, I’m a bit unsure on what happens next. Does the inverter just use the surplus to charge the battery, so if my house is using 1kW and the panels are generating 3kW, 2kW goes into the battery, then when the battery is full the surplus goes back to the grid?

The questions I can’t get my head around are:

  • Am I stuck with the scenarios listed above, i.e. the battery charges when it charges and discharges when it discharges or do different batteries/inverters have different features i.e. do they offer control?

  • I’m thinking for example if there’s a planned power cut on Thursday night, can I make sure the battery (through HA or other means) doesn’t use any of its charge during early evening (effectively drawing from the grid when I don’t need to) so it’s full and can run the house during the power cut?

  • How does a UPS-capable battery/inverter know to shut off if the RCD is tripped or turned off?

  • If I have a DC-side battery, and it’s not fully charged by the time the PVs stop generating, how can I charge it from the grid when the electricity is cheaper during the night, ready for use in the day?

Just trying to get my head around product selection - it’s a big expense and I don’t want to get it wrong.

Correct but I saw that the inverter can work in different modes and priorities depending on the scenario you want to cover (like frequent power outages), see below (extract from the user manual of the SolaX):

So for me, you have to ask those questions first to the professionals who gave you a quote, to see if the functionnalities you are looking for will be fullfilled natively by the inverter they proposed… Again, I do not think that HA will give you missing inverter functionalities, you have to make sure you have your PV array correctly set to cover all your scenarios… Now, is HA able to change the work mode of the inverter without going manually into the inverter menus ? That’s a question that can de discussed in this forum…and I don’t know the answer unfortunately…

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You’ve answered my question brilliantly, thanks and that confirms it - the ‘smarts’ are done by the inverter.

Will do some more digging, thanks again.

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Were you able to gain any insight into this question? My online research has led me thus far to Solar Assistant, which integrates into Home Assistant via MQTT I’m still not 100% that it can deliver the outcome raised in the above question.

I’ve been exploring the world of solar PV and battery storage lately, and it’s fascinating how much it can transform the way we use and think about energy. One website that caught my eye is pknergypower. They seem to have a range of solutions that could be beneficial for homes or businesses looking to go solar. I appreciate how it presents information in a clear and understandable manner, especially for those new to the technology. It’s crucial to have resources that simplify complex topics like solar energy, making it easier for everyone to understand and consider for their own needs.

I’m curious to hear from those who have already made the switch to solar PV and battery storage. What made you decide to take the leap? How has it impacted your energy usage and costs? Any advice for someone considering this change?
Also, if anyone has specific experiences with, I’d love to hear about them. It’s always helpful to get real-world feedback when considering a new energy solution.