Using15min interval data

4 posts / 0 new
Last post
Using15min interval data

Hi SAM, I am trying to use 15 minute interval data and have two questions on how to paste this data.
1. What is the format to import 15 minute interval?
2. Am I limited to using only 1 year? I currently have data from July 2012 to October 2015.
3. What is the correct format to copy this information (does it matter if I start with July or should it be January to January?)

Paul Gilman

Dear Carla,

1. SAM uses the SAM CSV format for weather files. You can find a description of the format in SAM's Help system, under Weather Data in the table of contents, or on the SAM website Weather data page under "Weather File Formats."

The SAM CSV format supports weather data with between one-minute and 60-minute time steps. SAM determines the time step from the number of weather data rows in the file. For sub-hourly data, be sure to include a Minute column in the file. The Minute column is necessary for sun position calculations.

2. Yes. SAM's simulation uses one year of weather data. If you have data for multiple years, you can run a separate simulation for each year. You can use the LK script to run simulations with multiple weather files, available for download on the Samples page to automate the process.

3. SAM is designed to work with a weather file that starts on January 1st and ends on December 31, so for best results, I would recommend using January-through-December data. SAM assumes the first time step is the first one of the year. For 15-minutes, the first time step would be the one that ends at 0:15. However, because the solar performance models use the time stamp data (Year, Month, Day, Hour, Minute) rather than the Row number for sun position calculations, the performance models should work with a weather file that starts at any time of the year. The financial models, on the other hand, require January-through-December data to apply time-of-use data to the correct time steps.

Best regards,


Hi Paul,

I thought that the first data point loaded into SAM had to be a Monday (not necessarily Jan 1) for time of use to know weekdays from weekends. Since weather won't be significantly different between January 1, say, and January 3, I move the first non-Monday days of data from the start of the load file to the end.

If you load actual January 1 data first, regardless of what day of the week it was on, it could result in SAM thinking that every weekend should have Wed/Thursday data, for example.

I don't think SAM understands actual calendars, right? Does this make sense?

Also, wouldn't the performance data have to be approximately synced with the weather data? If not, you could have June load and January weather...

Paul Gilman

SAM assumes that the first data row in the weather file is for the first time step on Monday, January 1, and uses that assumption to determine whether the current day is a weekday or weekend for the following:

  • Residential and Commercial financial models when you use time-of-use schedules on the Electricity Rates page
  • PPA financial models when you specify price multipliers on the Time of Delivery Factors page
  • Photovoltaic performance models when you include a battery in the system
  • CSP performance models with storage

If you are using the Residential or Commercial financial model, ideally, your weather data and load data should be consistent. For example, there may be a correlation between the load and solar radiation data for a building with air conditioning loads during summer months.

Best regards,

Theme by Danetsoft and Danang Probo Sayekti inspired by Maksimer