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I put solar on my home on the north west side of the Big Island. I calculated my estimated production using PVWatts and it was amazing close to my actual production for my first 6 months of monitored output. However, I recall that there were different weather data sets (TMY2, TMY3, etc.) on the PVWatts map that I could choose at that time.
I am building a new home about 13 miles away. Now when I use PVWatts, there are no other data sets for the Big Island. My only choice is the default NREL NSRDB grid cell for my location (Lat, Lon: 20.05, -155.86). To test the accuracy of this dataset, I moved the red pin to Hilo. When I repeated the calculations, the estimated output for my home's location was very similar if not identical to Hilo's location, 63 miles away. However, the weather is dramatically different in Hilo than at my home's location of the sunny, dry NW coast of the Big Island! Hilo has many more clouds and much more rain than we do! Has PVWatts changed so that now I don't have good estimated irradiance and weather data for my location? Getting the same results as a location in Hilo is next to worthless.
I am building a new home about 13 miles away. Now when I use PVWatts, there are no other data sets for the Big Island. My only choice is the default NREL NSRDB grid cell for my location (Lat, Lon: 20.05, -155.86). To test the accuracy of this dataset, I moved the red pin to Hilo. When I repeated the calculations, the estimated output for my home's location was very similar if not identical to Hilo's location, 63 miles away. However, the weather is dramatically different in Hilo than at my home's location of the sunny, dry NW coast of the Big Island! Hilo has many more clouds and much more rain than we do! Has PVWatts changed so that now I don't have good estimated irradiance and weather data for my location? Getting the same results as a location in Hilo is next to worthless.
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