Daylight Savings Time: What a Difference an Hour Makes

Daylight Savings Time(DST) & ISO Data

Twice a year, those that collect and manage data, face the dreaded extra or missing hour – in the spring when we "spring forward," and in the fall when we “fall backwards.” On the Short Day in spring most ISOs publish only 23 rows of data. On the Long Day in the fall most ISOs publish 25 rows of hourly data. And each ISO handles this differently – and this is true not only across ISOs but within ISOs. We've learned there are special nuances for each ISO website. 

Considering we're collecting data from hundreds of websites, these two dates create a lot of work. For Yes Energy this work happens in our Market Data Ops team. This team of superheroes monitors the data when it comes in – starting with forecasts earlier in the week, day-ahead on Saturday, real-time results on Sunday, and final/revision files after the DST date. We take this so seriously that our team stays up and watches the data load in the database and updates in QuickSignals to confirm that we capture all of the data. We run secondary proofs on the raw data in the days and weeks following DST as well.

Since DST changes our behavior so much we wondered how does it change the behavior of market participants in the virtual market. We took a look at our data to answer “Does Daylight Savings Time impact the participants in the virtual markets?” Here’s a look at what we found.

This chart shows the virtual supply MWs by ISO. Daylight Savings was on 11/3. On this day, most ISOs had lower supply MWs than other days in October and thus far in November.