Sizing an inverter.

[rich1]

Are there any benefits of going for, say an 8kw inverter over a 5kw, with a solar PV and battery system?

I assume a 5kw would pull additional power from the grid if demand exceeds 5kw, rather than just switching 100% to grid supply?

I'd also assume that an 8kw inverter will be less stressed running at 4kw than a 5kw?

Our usage is, like most peoples, usually well under 5kw, but there are obviously combinations of applicances that can push the demand towards 8kw for short periods.

Is having a big enough inverter to cover these periods worth the extra cost?

If managing peak load to keep it below the inverter max is important, is there a system of 'smart' power sockets which will load shed to try and keep peak load down to some set limit?

 

[binky]

Generally I would size the inverter to suit the PV array. Once you have done that, then look at outputs to the house. Peak loads don't tend to last very long, like boiling a kettle, wiping out loads like washing machines that run for long periods of time, fridges, freezers etc tends to be where you get your savings.

 

[Kot]

Generally I would size the inverter to suit the PV array. Once you have done that, then look at outputs to the house. Peak loads don't tend to last very long, like boiling a kettle, wiping out loads like washing machines that run for long periods of time, fridges, freezers etc tends to be where you get your savings.

And consider a battery, better to fill that up with excess solar, to then use your own power when the sun goes down. You can then charge the battery at low peak in the early hours and during the day export earlier at a higher mid peak or high peak export rate. Consider changing to Octopus

 

[Andy1733]

I would say it depends on your usage and especially the spikes in usage.

My house base line ticks over at around
0.5 - 0.6kwh every hour.
Then around 5pm is where we get the spikes before dropping back to 0.6
My 3.6kw inverter and battery combo covers most of the usage from march to oct. though I am limited to cover the spikes
If I knew what I know now I would have gone bigger with the inverter 5kwh. Keep the 4kw of panels, And add 1 more battery to take me to15kw..
Then charge the battery on the cheap rate and milk them all day.