Portland General Electric Schedule 85 bills two separate demand charges: on-peak demand and off-peak demand with different rates per kW. On-peak is roughly 3x the off-peak rate. Client is a food processing plant that runs three shifts. Their on-peak demand and off-peak demand are nearly identical because production runs 24/7. Is there any way to shift demand to reduce the on-peak portion?
On-peak vs off-peak demand ? billing both separately
Linda ? for a 24/7 operation the demand profile is what it is. You cant really shift production demand. But check whether non-production loads like HVAC, lighting, and compressor cycling are adding to on-peak demand unnecessarily. Pre-cooling the facility before the on-peak window starts can reduce HVAC demand during peak hours. Its the controllable loads on top of base production that create optimization opportunities.
PGE defines on-peak as 6am-10pm Monday-Saturday for Schedule 85. Thats a very wide on-peak window compared to some utilities. Xcel in Minnesota uses 9am-9pm weekdays only. The wider the on-peak window, the harder it is to shift load. For a 24/7 operation on PGE, youre basically paying on-peak demand rates for 16 hours every day including Saturdays.
Good point Steven about the Saturday inclusion. My client doesnt run full production on Saturdays but the HVAC and lighting are still active. If they could reduce Saturday load significantly that might lower on-peak demand since Saturday is included in the on-peak window. Ill pull the interval data to see if Saturdays are actually setting the peak.
Natalie ? thats an unusual and beneficial tariff structure. In Sacramento, SMUD TOU rates bill demand only during the on-peak period. Off-peak demand isnt billed at all. So a client who can shift ALL demand to off-peak pays zero demand charges. Practically impossible for most businesses but Ive seen cold storage facilities that shut down compressors during on-peak and coast on thermal mass.
Update: pulled 15-minute interval data for 6 months. Saturdays ARE setting the on-peak demand peak about 40% of the time because the BAS system runs full HVAC on Saturdays even when the plant isnt in full production. Reprogramming the BAS to reduce Saturday HVAC load could lower on-peak demand by an estimated 85 kW. At PGE on-peak demand rates thats approximately $11,000 annual savings.
Linda ? $11,000 from a BAS schedule change on Saturdays is a clean finding with zero capital cost to implement. This is the kind of operational adjustment that makes demand charge auditing valuable beyond just finding billing errors. The bill was technically correct but the client was paying more than necessary due to controllable operational decisions.
In Boise, Idaho Power Schedule 19 has a unique approach ? they bill on-peak demand but give a credit for off-peak demand that exceeds on-peak. The theory is that if your off-peak load is high you are helping the utility utilize off-peak capacity. A 24/7 plant actually benefits from this structure because the flat load profile generates off-peak credits. Check if PGE has anything similar.