Phoenix summer heat is killing us with APS demand charges. Our client has a 200-ton chiller that draws 350 kW during normal operation but spikes to 520 kW during startup. That's an extra $2,100/month in demand charges on their Schedule E-32 rate. The chiller has to restart multiple times per day due to building automation issues. Has anyone dealt with APS on reducing demand charges for essential equipment like chillers? Their time-of-use rates are brutal during summer peak hours.
APS demand charge nightmare - chiller startup eating our lunch
Sarah, APS is tough but they do have some demand response programs. We deal with similar issues in San Antonio with CPS Energy. First question - is that a scroll, screw, or centrifugal chiller? Scroll chillers have the worst startup characteristics. You might want to look at a soft-start controller or variable frequency drive if it's not already equipped. Also, what's causing the multiple restarts per day? That sounds like a control system problem that needs fixing first.
Had the exact same problem with PG&E up here in San Jose. 180-ton screw chiller was creating 200 kW demand spikes every restart. We ended up installing a Danfoss soft-start system for about $8,500 and it cut the startup demand by 45%. ROI was 8 months. The key with these utilities is documenting your baseline and showing the improvement. APS might be willing to work with you if you can prove you're making efficiency investments.
Angela - it's a York screw chiller, about 12 years old. The multiple restarts are happening because the building automation system has some sensor issues and keeps overshooting setpoints. Facilities manager says they're getting those fixed next month. Pete - $8,500 sounds reasonable for that kind of savings. Did you have to get utility approval for the soft-start installation, or did PG&E just credit you automatically once they saw the reduced demand?
Sarah, fixing those BAS issues should be your first priority. Here in Kentucky with KU, we had a client spending $1,800/month extra just because their chiller was short-cycling due to bad sensors. Once we fixed the controls, the demand charges dropped by 60% without any equipment changes. Soft-starts are great but you need stable operation first. What kind of sensors are failing - temperature, pressure, or flow?
Don't overlook thermal storage either. With APS's crazy time-of-use rates, making ice at night and using it during peak hours can eliminate those demand spikes completely. Georgia Power offers rebates for thermal storage systems here in Atlanta. Might be worth checking if APS has similar programs. The upfront cost is higher but you're basically shifting your cooling load to off-peak hours when both energy and demand charges are lower.