Electricity production over time.

[Cshama]

I had my system installed last month.

According to pvwatts it was supposed to.profuce 2500kw for the month of June. Instead I am getting closer to 2900kw.

Can I assume that pvwatts is 20% low all year or too soon.

 

[wjgjr]

It is way too soon to assume that. PVWatts is based on typical weather over recent history, so if the month was sunnier or cooler than typical, your numbers may be unusually high. For my install in MD, June looks like it might be our best month so far of our 11 relative to PVWatts (competing with April) due to some cooler weather and a lot of sun. Additionally, it has been noted that PVWatts does not take into account shading issues that might impact production more in the winter. With almost a year in, my system is generally doing better relative to PVWatts estimates in the summer than winter, but we will see if that remains true over time.

20% is definitely a very good number and I would guess is a good sign you will over-perform the PVWatts number, but I would not assume it will be 20% over. Weather on the east coast (unlike a lot of posters who are in more desert-like climates out west with much more sun) can certainly produce very unpredictable results.

 

[jimm01]

Weather on the east coast (unlike a lot of posters who are in more desert-like climates out west with much more sun) can certainly produce very unpredictable results.

Especially when coastal lows pop up or cloud cover occurs during peak periods then clears out during at normal hours of low production.

 

[h2ofun]

I had my system installed last month.

According to pvwatts it was supposed to.profuce 2500kw for the month of June. Instead I am getting closer to 2900kw.

Can I assume that pvwatts is 20% low all year or too soon.

I spend no time with PVwatts? why, since what I am getting is what I am getting, and nothing is going to change that.

 

[holeydonut]

I think with this wacky weather out West with so much sunlight and almost no cloudcover ... anyone who is generating at or below the PVWatts estimate may have an issue that is worth investigating to see if their system is performing normally.

Or, having some panel level detail to assess whether shading issues or maybe a bad panel is in play. This data helps the homeowner gain confidence in the performance of your big investment.