Client is considering battery storage to reduce demand charges. As an auditor, not an engineer, how should I evaluate whether the demand charge savings justify the battery investment? And are there any billing implications of adding storage that I should warn the client about?
Battery storage and demand charges
Your role is to quantify the demand charge savings opportunity. Use the interval data to identify the peak demand events — how high, how long, how often. Then model what the demand would be if those peaks were shaved by a battery. The difference in demand charges is the annual savings the battery needs to justify. Don't recommend the battery itself — give the client the savings number and let them work with a storage vendor on the hardware. As for billing implications, some utilities have specific tariff provisions for behind-the-meter storage. Check whether the utility requires a separate meter on the battery, whether storage discharge counts as generation (triggering standby charges), and whether the rate schedule changes when storage is added.
Solid advice. I'd add one important caution: demand charge reduction from batteries works best when the peaks are sharp and predictable — like a chiller startup every morning. If the demand profile is flat and high, batteries won't help much because you'd need enormous storage capacity to meaningfully reduce a sustained peak. The interval data analysis is the starting point. If the peaks are sharp and short, there's a strong case. If the load is flat, storage probably isn't the answer and the client should focus on rate optimization instead.
Ran the interval analysis. Client has a clear 30-minute morning peak from elevator motors and HVAC startup that's 180 kW above their sustained load. Rest of the day demand is steady. Battery could shave that peak and save about $2,800/month in demand charges. Passing the numbers to a storage vendor for sizing and pricing.