Which wattage of inverter to pick?

[Bob Smith]

Thanks for that, it seems from all the quotes I’m getting are using JA panels, wonder if that‘s just because of availability?
so might be settling for;

16 x 410w All Black JA Solar panels
10kwh Puredrive Battery
6kw Solis Hybrid Inverter
K2 Tile roof mounting system
Eddi Hot Water Divertor
Bird Protection

HI SolarNoob

I am looking for installers and recommendations. Would you mind share the one you selected? Thanks (I know some only serve their local area. For info. I am in the north-west)

 

[Bob Smith]

Hi there. I've pretty new to the forum, as in <24 new. I'm in the process of trying to understand how to submit a DNO to UK Power Networks and noticed you mentioned a "portal for low carbon applications." Just wondering whether you might be able to clarify where this is. Currently finding it a challenge to complete the A1.1 document, as I plan to remove an AC inverter and replace with hybrid. Thanks

Are you staying within the 3.68kW limit? If so you will only need G83 form but you obviously already have a system in place? Have you contacted your DNO directly, they will help you with whatever forms you need.

 

[Takemetocourt]

That'll be the export limit but you could have a larger inverter. I've gone for the 6kw Solis Hybrid for a few reasons but I'll have to limit its export to 3.6kw.

Not a big deal as I don't really want to export anything at just 5ppkw.

How do you limit export?

 

[Berserkerboy]

It's a setting on the inverter. So the inverter above can supply 6kw to your home circuits but you set it up to send a maximum of 3.6kw back to the grid. It does this by sensing which way the electrical flow is going.

 

[Bob Smith]

What happens to the electricity generated which can't be stored because the batteries are full, can't be used by the home because the home already has what it needs, can't be used to heat the water because it is already heated and can't be exported because the limit has been reached?

I supposed the trick is to design a system that will size the batteries (only real buffer in that story) so the export limit is rarely reached to avoid wasting generated electricity.

 

[Berserkerboy]

The inverter effectively shuts down the panels to only allow the limit it has been set to as I understand it.

 

[Bob Smith]

The inverter effectively shuts down the panels to only allow the limit it has been set to as I understand it.

Thanks for confirming what I thought. Therefore it is, in my view, critical to size correctly the batteries in order to have the less waste as possible (ie inverter shuts down the panels and it is still very sunny!)

 

[Berserkerboy]

Yes.

If you're retrofitting you'll have a better idea of size battery you need.
We use around 3kwh/day from the grid during the sunnier months. I also looked at our production during the other months as it would be pointless overspending on a bigger battery that won't get filled up.
I've decided on a 5kwh battery and 3kw AC coupled inverter (around £2000). My grid usage for the majority of the year will hopefully be...zero!.
At the moment, I know that the economics of installing the battery are only just making sense. However, if prices continue to spiral as appears likely, then that will change. Also, the battery will mean that we won't have to time using high-consuming items with the sun being out. That'll make life a bit easier.
I also recognise that winter months will require most of our power to come from the grid, as will be the case with most systems.

 

[Bob Smith]

Thanks @Berserkerboy

I think to remember that from about May until September we import about 4kWh/day but I am not sure. What I know for sure is that since 2019 we imported an average of 15kWh. I have no idea what the actual house consumption is. I can only measure what I import. (I know what I generate but not what I use from what is generated).

I am planning for about 10kWh battery storage to start with. This will obviously be too large for my current 4kWp but I intend to add more panels. I am not sure how much yet, I have two options
Option 1: About 4.5kW but the panels will be facing 3 different directions (SSE, S and WWS (but those will be on a wall good for Winter though)
Option 2: Same as 1 + about 12 panels facing NNW (about 6kW)

What I am trying to do is to spread over the day the generation. Unfortunately, there is nothing I can put facing East. The NNW is not ideal but from Mai until August they should be generating their fair bit of electricity and if the batteries are full, I'll export.

I am still in the design phase and without a committed installer, it is difficult to progress...

 

[Berserkerboy]

My first thought is that you will be creating some serious generation and exporting a lot during the summer months, even with option 1. The 4kwh you draw from the grid is mostly your evening and nighttime use. I suspect that you are exporting more than that during the day with your current system, which you could store in the battery and use in the evening and nighttime.
I would install the battery and see how you go without putting in extra panels first. Option 2 seems like overkill to me. The northern-facing panels would only generate reasonable power during the summer months when you already have too much coming in anyway.

 

[Gian]

Yes.

If you're retrofitting you'll have a better idea of size battery you need.
We use around 3kwh/day from the grid during the sunnier months. I also looked at our production during the other months as it would be pointless overspending on a bigger battery that won't get filled up.
I've decided on a 5kwh battery and 3kw AC coupled inverter (around £2000). My grid usage for the majority of the year will hopefully be...zero!.
At the moment, I know that the economics of installing the battery are only just making sense. However, if prices continue to spiral as appears likely, then that will change. Also, the battery will mean that we won't have to time using high-consuming items with the sun being out. That'll make life a bit easier.
I also recognise that winter months will require most of our power to come from the grid, as will be the case with most systems.

Hi I have a 5kw battery and my hardware allows a max of 2kw load from the battery. In all fairness my 5kw battery needs to be 15kw to run my home how I want it. I know every home will have differant usages . My 5kw battery is hooked to a 4 KW array and in winter months ,I should say poor light months it sometimes only charges to 40% so my battery is a waist in poor light . Which is a good 4 months a year. I would see a 15jw battery using newer tech so the battery could also be charged using cheap rate electric would work better.

 

[Gian]

My first thought is that you will be creating some serious generation and exporting a lot during the summer months, even with option 1. The 4kwh you draw from the grid is mostly your evening and nighttime use. I suspect that you are exporting more than that during the day with your current system, which you could store in the battery and use in the evening and nighttime.
I would install the battery and see how you go without putting in extra panels first. Option 2 seems like overkill to me. The northern-facing panels would only generate reasonable power during the summer months when you already have too much coming in anyway.

My own rethink this year is to actually do the same and fill roof space that will only get a slot through the day. So I intend to fill roof space with solar , I will do this my self to keep cost to a minimum. I will hook timers on each system to control when I want it to work. It's really for poor light or winter, the more solar the more charge. I am working out how I would control my 3 seperate systems in good light , I am thinking of using light cells which I can include into my timers, it's still in my design stage but plan this next year using all used equipment. I already have 8 KW on South facing roof. This project is really to make battery's work in poor light. My plan is to add another 6kw to 3 separate roofs so I first light gets covered for 3 hours second for 2 hours and 3rd would be the last 3 hours late afternoon onwards.

 

[Berserkerboy]

I agree. I have only really taken into account making the most of our solar power.
The ability to charge using cheap rate electricity is something else to take into account. It's something I could do by adding more batteries at a later date.
We are presently with EON on their consumer-protected rate, with a smart meter installed within the last year. What would be the best way forward if I wanted to take advantage of cheap rate power now?

 

[Bob Smith]

My first thought is that you will be creating some serious generation and exporting a lot during the summer months, even with option 1. The 4kwh you draw from the grid is mostly your evening and nighttime use. I suspect that you are exporting more than that during the day with your current system, which you could store in the battery and use in the evening and nighttime.
I would install the battery and see how you go without putting in extra panels first. Option 2 seems like overkill to me. The northern-facing panels would only generate reasonable power during the summer months when you already have too much coming in anyway.

Hi,
Back in March, I was thinking about batteries only. I was first told it was not possible to retrofit. I now know it was rubbish as you can retrofit anything (if not DC which would have killed my FiT, then AC coupled batteries).
As weeks passed, I had more thought and also I learnt that for new PV system there would be no VAT from April. I thought OK, I could have Panels + batteries no VAT. I had in the past considered some panels on my wall facing west (for the simple reason to catch light my original panels could not).
And then one thing to another, I thought well if I install panels here, what not panels there.
I have also learnt about the agile tariff.
Therefore, I think (it will depend on the cost and what DNO says) but I could take best of both worlds. ie get enough panels in different directions to charge ma batteries easily and sell the excess electricity. The more excess the better.

This is where I am at the moment.

I agree that the panels facing NNW will not generate much compared to my SSE panels. This said, my SSE panels are from 2016 with an efficiency of 15%. My uncle installed last April panels facing W and E for a 4kWp system and during this period he generated 2MWh with June alone 661kWh, while I generated since April 1.8MWh with June 531kWh. This is to say that the new system will, performing better, will compensate a bit its less ideal orientation. And this is extra electricity. I am not trying to decide if I should place planes South or North. The best spot is already taken

So far I have no quote nor do I know what the DNO will say if I want to add 8kW on top of my existing 4kW.

Of course, if they want to limit my export, and I do not want more batteries, then maybe I will downsize because I do not want too much electricity going to waste. As mentionned in another reply, the trick is to balance what can be:

1. directly used,
2. stored
3. exported
4. with minimum waste if a limit must be applied

 

[Bob Smith]

My own rethink this year is to actually do the same and fill roof space that will only get a slot through the day. So I intend to fill roof space with solar , I will do this my self to keep cost to a minimum. I will hook timers on each system to control when I want it to work. It's really for poor light or winter, the more solar the more charge. I am working out how I would control my 3 seperate systems in good light , I am thinking of using light cells which I can include into my timers, it's still in my design stage but plan this next year using all used equipment. I already have 8 KW on South facing roof. This project is really to make battery's work in poor light. My plan is to add another 6kw to 3 separate roofs so I first light gets covered for 3 hours second for 2 hours and 3rd would be the last 3 hours late afternoon onwards.

Thank you Gian,
I am glad to see we have the same vision. Trying to generate as much as possible with the space available.