Path-Q Solar
How does a demand charge affect the value of solar for a small business?
Answer
A demand charge can make solar's value depend on whether generation reduces the business's highest measured power demand during the billing intervals used for billing, not merely on total energy produced. Solar may reduce some daytime peaks, but a battery, load management, or schedule changes may be needed to control peaks that occur when solar output is low.
Key points
- Energy charges are based on consumption over time, while demand charges are based on a measured peak or related demand metric.
- The relevant peak may occur before solar output is high, late in the day, or during a short equipment-startup event.
- Interval load data is important for identifying whether solar can coincide with the business's demand peaks.
- The value of storage depends on its ability to discharge at the right times and on the applicable demand calculation.
What it depends on
- Current tariff and demand-charge definition
- Interval load profile and operating schedule
- Solar production timing and system size
- Battery capability and control strategy
- Future business loads and rate changes
Risks and trade-offs
- Annual energy offset can look attractive while demand charges remain largely unchanged.
- Battery controls that target demand peaks may require careful commissioning and monitoring.
- Demand-charge savings can be uncertain if peaks are unpredictable or tariff rules change.
Information you may need
- Recent bills showing demand charges and billing determinants
- Interval electricity data
- Operating schedule and major equipment events
- Solar-only and solar-plus-storage simulations
- Current tariff documentation
Your next step
What to do next
Have a provider model the tariff using interval data and show separately how solar, storage, and load management affect energy charges, demand charges, and total cost.
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Some details may depend on your location, installer, utility, incentives, regulations, or specific property.
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