Questions for Solar Installation Sales Interview

Spies

Solax are definately 10 years (expressed as 120 months in their warranty information).

https://www.solaxpower.com/uk-warranty-policy/

arty688

2nd_time_buyer said:

... despite undersizing inverters being the norm. I am now inclined to turn the question around and say "why wouldn't you get an inverter to match the panel output?"

If you can cap the power exported to the grid to 3.68kw (if necessary). The difference in cost between a 3.68kw and 5kw inverter is typically in the region of only £100. Intrinsically it feels better not to be running something close to capacity for long periods.

All the research I have done no expert has recommended having an inverter the same size as the pv array. They seem to say the extra generation you get at lower light levels ( most of the year) out weighs the losses from the clipped solar. Partly this is to do with the fact that generation you get at the shoulder of the curve is more likely to be used so is more valuable Also I don’t think the reliability of the inverter is not affected. 

[Deleted User]

arty688 said:

2nd_time_buyer said:

... despite undersizing inverters being the norm. I am now inclined to turn the question around and say "why wouldn't you get an inverter to match the panel output?"

If you can cap the power exported to the grid to 3.68kw (if necessary). The difference in cost between a 3.68kw and 5kw inverter is typically in the region of only £100. Intrinsically it feels better not to be running something close to capacity for long periods.

All the research I have done no expert has recommended having an inverter the same size as the pv array. They seem to say the extra generation you get at lower light levels ( most of the year) out weighs the losses from the clipped solar. Partly this is to do with the fact that generation you get at the shoulder of the curve is more likely to be used so is more valuable Also I don’t think the reliability of the inverter is not affected. 

I had this discussion with my installer as I have a 7kWp array and a 5kW SolarEdge inverter. Two graphs later, I had my answer which is in line with your response. That said, seeing the peak output flatline for an hour on a nice sunny and cool day in May makes one wonder why we don’t have seasonally adjustable inverters?

Verdigris

I suppose as panel efficiency drops, over time, the clipping will become less. Mind you, the inverter would probably need changing before panel output and inverter capacity matched.

Exiled_Tyke

arty688 said:

All the research I have done no expert has recommended having an inverter the same size as the pv array. They seem to say the extra generation you get at lower light levels ( most of the year) out weighs the losses from the clipped solar. Partly this is to do with the fact that generation you get at the shoulder of the curve is more likely to be used so is more valuable Also I don’t think the reliability of the inverter is not affected. 

I also agree with this. Last year I was looking at the accounts of Bluefield Solar the and noticed  that they state for the UK they over spec panels to inverter capacity at between 1.2 and 1.4 times to make the best of poor generation here.  At the top end that's a lot great differential between panels and inverter than I would ever have anticipated but if that's what a business reckons is going to get the best returns than I'm quite happy to accept it.