This free tool lets you calculate peak solar/sun hours by month at any location in the US. The data might help you determine your solar system requirements.
How to use this Calculator?
Using this calculator is very simple. In the address field below, type your street address or city or zip code, or state and select the nearest match from the drop-down list. Then press submit button and you will be shown a table where the first row is the month and the second row is sun hours.
For international data, use the PVWatts government website
Pro tip: For better results, enter zip code in the address field
If you want to calculate the worst-case peak Sun hours, pick the lowest entry in the table. That would be the month which receives the least amount of sun hours. If you are planning to buy a solar system to offset your electricity entirely, you might have to consider the worst-case Sun hours for your calculation.
The data is obtained from NREL.gov and it is quite accurate. There may be a slight difference in the real-world data but the difference will be negligible unless you are using it for advanced research. We will be improving this tool over time and if you have any suggestions, feel free to contact us.