Auditing a regional grocery chain in Memphis ? 8 stores on MLGW commercial rate. Every store runs compressor racks 24/7 for refrigeration. Load factor is very high (85%+). But the demand charges are substantial because the compressor defrost cycles all sync up and create simultaneous peaks across multiple racks. Single store peak demand jumps from 280 kW baseline to 410 kW during coordinated defrost events. Thats 130 kW of demand charge penalty from defrost scheduling alone.
Grocery store refrigeration ? constant load but huge demand charges
Frank ? defrost scheduling is the number one demand charge issue in grocery. When all racks go into defrost simultaneously the electric reheat elements create massive coincident peaks. Solution is staggering defrost cycles so no more than one rack defrosts at a time. Most modern rack controllers can do this but the default setting is often simultaneous midnight defrost.
Edward ? checked with the store maintenance team. Youre right ? all six racks in each store are set to defrost at midnight simultaneously. Thats the factory default. Nobody ever changed it. Staggering them to defrost sequentially would spread the peak across 3 hours instead of hitting all at once.
Mitchell makes a great point about anti-sweat heaters. Ive also found grocery stores where the backup emergency generators do a weekly test under load during on-peak hours. That generator test adds 150-300 kW of demand on top of normal store load for 30-60 minutes. Moving the generator test to off-peak hours or to a lower load test setting eliminates that demand spike entirely.
Thomas ? generator testing! Confirmed two of the eight stores run generator tests on Tuesday at 2pm which is dead in the on-peak window. Moving to Sunday at 6am eliminates that spike. Between defrost staggering, anti-sweat heater optimization, and generator test rescheduling, Im projecting $8,200-11,500 per store in annual demand charge savings. For 8 stores thats $65,000-92,000 total.
I work with grocery and convenience store accounts in Corpus Christi. AEP Texas interval data clearly shows the defrost spikes. Another thing to check ? anti-sweat heaters on display cases. Many stores leave anti-sweat heaters running 24/7 on high when they only need to run during humid periods. Reducing anti-sweat heater operation can cut 40-60 kW off peak demand in a typical grocery store.
Final update on this chain ? implemented all three recommendations across all 8 stores. Actual savings after 6 months of data: $9,400 average per store. Annual run rate of $75,200 for the chain. My contingency fee was 40% of first year savings. Very profitable engagement from demand optimization alone with zero capital expenditure.