Alliant Energy client in Cedar Rapids. Manufacturing facility with 450 kW peak demand. Demand charges run $5,400 per month. A battery storage vendor is proposing a 200 kW / 400 kWh system to shave peak demand to 250 kW. Projected demand savings of $2,400 per month. Battery system cost: $280,000 installed. Thats a 9.7 year payback on demand savings alone. Is anyone seeing better economics?
Battery storage for demand charge management ? is the math there yet?
Joanne ? battery economics for demand charge management depend heavily on the demand charge rate and the required discharge duration. A 200 kW system needs to discharge for the entire peak period ? if that peak lasts 2 hours the battery needs 400 kWh of capacity. If the peak lasts 4 hours it needs 800 kWh. Capacity drives cost. For a facility with a sharp narrow peak, smaller batteries work. For broad plateaus, the economics deteriorate quickly.
In California, PG&E demand charges are $20-25 per kW on commercial tariffs. At those rates the same 200 kW battery saves $4,000-5,000 per month ? payback drops to 4.5-5.5 years. Plus California has SGIP incentives that cover 25-50% of battery cost. After incentives the payback is 2-3 years. The economics are territory-dependent.
Phyllis ? $20-25 per kW demand charges? Alliant is $12 per kW. California economics are completely different. So the question for my Iowa client is whether demand charges will increase enough over the 10-year battery life to improve the economics.
Another angle ? batteries for demand management also provide backup power during outages. If the facility values backup power, the battery serves dual purpose. The demand management savings partially offset the cost of what would otherwise be a pure backup investment. I frame it to clients as getting demand savings as a bonus on top of backup power, not battery storage justified by demand savings alone.
From the engineering side ? dont forget battery degradation. Lithium-ion batteries lose 2-3% capacity per year with daily cycling. A 200 kW system delivering 200 kW in year 1 only delivers 175-180 kW in year 5. The demand management benefit declines over time. The payback calculation should use degraded capacity projections, not nameplate capacity for the full system life.
Hector ? excellent point about degradation. The vendor projected savings using nameplate capacity for 10 years. Adjusted for 2.5% annual degradation, the cumulative savings over 10 years drop by about 15%. Payback extends from 9.7 years to 11.4 years. At that point the battery warranty is expiring. The math doesnt work for this Iowa client at current demand rates.
Joanne ? the economics dont work for standalone demand management in low-demand-charge territories today. But watch for utilities adopting demand charges on smaller commercial accounts that currently have no demand charge. If Alliant introduces demand charges for accounts under 200 kW ? which several utilities have done recently ? the addressable market for battery demand management expands dramatically. The technology is ready; the tariff economics need to catch up.
Outstanding analytical thread. Battery storage for demand management is economically viable today in high-demand-charge territories (California, Hawaii, parts of New York) and for specific applications like narrow-peak facilities. In moderate-demand-charge territories the economics are marginal. In low-demand-charge territories theyre not there yet. Joannes honest assessment of the Iowa math, Hectors point about degradation, and Natalies dual-purpose framing represent the three perspectives auditors should present to clients asking about battery storage. Never recommend based on vendor projections without independent verification.