When requesting interval data, should I ask for 15-minute intervals or hourly? I've been getting hourly but someone told me 15-minute is much more useful for identifying demand spikes. Is the extra granularity worth the bigger dataset?
15-minute vs hourly data — does it matter?
Always get 15-minute if available. Demand charges are typically based on the highest 15-minute or 30-minute demand interval in the billing period. If you only have hourly data, you're seeing an average across four 15-minute intervals. A demand spike that lasts 15 minutes and costs your client $2,000/month in ratcheted demand charges is completely invisible in hourly data because it gets averaged out. I had a cold storage facility on Xcel Energy where hourly data showed steady 400 kW demand but 15-minute data revealed a 15-minute spike to 680 kW every morning when all the compressors kicked on simultaneously. Staggering the startup sequence eliminated the spike and saved $3,100/month.
I agree — always request 15-minute data. The demand spike identification alone justifies the larger dataset. Most modern Excel versions handle 35,000 rows of 15-minute data (one year) without any problems. The other advantage of 15-minute data is that it lets you accurately model alternative rate scenarios. If you're evaluating whether your client should switch to a time-of-use rate, you need 15-minute data to calculate what their bill would have been under the TOU rate. Hourly data is too coarse for accurate TOU modeling because the on-peak and off-peak periods often start and end on the quarter hour.
Makes total sense. Switching all my data requests to 15-minute going forward. The cold storage example really drove the point home.