Inverter Size for Battery Output

[Jimglasgow]

I thought I had an understanding of how to size an inverter but I think I have become slightly confused after taking to some proposed installers. I am looking at a 15 panel solar array with a proposed output of 6150KWH and was thinking of having two 6.5KWH batteries that would have their charge delivered via solar and when required off peak through our Octupus Tarrif.

Our daily consumption is around 16-18kwh so I have no intentions at this stage to be fully self efficient. At times due to our Hot Tub having with a 1KW heater we can peak around 4KW when a few appliances are on at times. So this all explained my understanding was to get an inverter that has enough discharge/charge rate to facilitate the above 4KWH to draw enough power from the battery when needed.

However today I was told that the Solar Array is what decided the size and here is where the confusion comes in and is where I need some guidance.

Noting the solar array is 6150kwh and what I was advised today the only inverter I see it’s one at 6Kwh therefore would it throttle the transfer on a good day or has this not been explained correctly.

If my solar array is bringing 6150kWh on a good day and I want to draw around 4KWH off the battery when needed what should I consider size wise for my inverter….. a 4KWH?

I should have said both proposals are Growatt Inverters and Batteries.

Any advice would be welcomed

 

[kropaske]

Given you are planing to install 6.15kwp array your inverter should be sized to match this output. Installing 4kw inverter would mean that in good day a lot of energy generated by the array would be wasted. Also it is likely that size of this array is bigger then inverter allowable input. Therefore you should install 6kw inverter which will fully utilize your array size. Inverter output size is one of several different parameters that needs to be taken in to account when sizing inverter but your installers will select correct one to match to your array arrangement. Also this will fall under g99 so permission from DNO needs to be obtained before connection to their network is made.

 

[Jimglasgow]

Given you are planing to install 6.15kwp array your inverter should be sized to match this output. Installing 4kw inverter would mean that in good day a lot of energy generated by the array would be wasted. Also it is likely that size of this array is bigger then inverter allowable input. Therefore you should install 6kw inverter which will fully utilize your array size. Inverter output size is one of several different parameters that needs to be taken in to account when sizing inverter but your installers will select correct one to match to your array arrangement. Also this will fall under g99 so permission from DNO needs to be obtained before connection to their network is made.

Thanks noting your answer it looks like I must have picked it up wrongly from the start. So based it what you have said I should opt for a 6K inverter with a view I will loose 150watts on a good day….. yes

 

[kropaske]

Having 6.15kwp array does not mean it will generate that. There are many factors to consider such as orientation, angle, temp, wind, irradiance and so on. So, no you wont loose 150w as its very unlikely that your array will generate at quoted value.