How Solar and Battery Storage Reduce Demand Charges for Temecula Businesses

Adrian Marin|Independent Solar Advisor, Temecula CA

Helping Riverside County homeowners navigate SCE rates and solar options since 2020

Most business owners who get a solar quote focus on their monthly kWh consumption and calculate savings based on how much of that usage solar can offset. That math works fine for residential accounts and small commercial accounts on basic rate schedules. But if your Temecula or Murrieta business is on an SCE commercial TOU rate and you have been ignoring the line item labeled "demand charge" on your bill, you may be leaving the largest single savings opportunity untouched. Understanding demand charges - and why solar alone does not fix them - is the starting point for any serious commercial energy analysis.

What Is a Demand Charge?

Your electricity bill has two fundamentally different types of charges. Energy charges are what most people think about: you pay for every kilowatt-hour (kWh) of electricity you consume. The more you use, the more you pay, and solar panels directly reduce this cost by generating on-site power.

Demand charges are different. They are based on your peak power draw - measured in kilowatts (kW), not kilowatt-hours - during the billing month. SCE measures your demand as the highest 15-minute average power consumption recorded anywhere during the billing period (or during specific on-peak hours, depending on your rate schedule).

The demand charge rate is a fixed dollar amount per kW of that peak reading. So if your business hits a peak of 50 kW during a single 15-minute window on one afternoon in August, you pay the demand charge rate multiplied by 50 kW - for the entire month. It does not matter that you ran at 15 kW for the other 99.9% of the month. That one peak defines your monthly demand charge.

Why does the utility do this? Because the electrical grid must be built to handle everyone's peak simultaneously. A customer who draws 50 kW at peak requires the utility to have 50 kW of infrastructure capacity available for them, even if they rarely use it. Demand charges recover that infrastructure cost.

SCE Commercial Rate Schedules: TOU-GS-1, TOU-GS-2, and TOU-GS-3

Southern California Edison uses General Service (GS) rate schedules for commercial and small industrial customers. Which schedule applies to your business depends primarily on your peak demand. Here is how the tiers break down:

TOU-GS-2 is the rate schedule most commonly affecting mid-size Temecula businesses: restaurants, medical practices, veterinary clinics, fitness centers, and automotive service shops. At TOU-GS-2, the demand charge structure has multiple components:

• On-peak demand charge: applies to the highest 15-minute demand recorded during the on-peak window (4 to 9 pm weekdays), approximately $19 to $24/kW in summer months
• Mid-peak demand charge: applies to demand in mid-peak hours, lower rate
• All-period (facilities) demand charge: applies to the highest demand across all hours, not just peak windows, typically $4 to $8/kW

This layered structure means that a single spiky load event - an HVAC compressor startup, a commercial kitchen all firing at once, a welding machine or lift in an auto shop - creates demand charges across multiple components simultaneously.

Why Solar Alone Often Does Not Eliminate Demand Charges

Solar panels generate electricity proportional to sunlight. In Temecula, they produce at or near full capacity between roughly 9 am and 3 pm on clear days. That production profile lines up well with many daytime commercial loads and substantially reduces energy charges.

But demand charges are determined by peak power draw, not total energy consumption. The peak that determines your on-peak demand charge on TOU-GS-2 occurs somewhere in the 4 to 9 pm window - after solar production has declined significantly. A Temecula restaurant that runs its kitchen at full capacity for dinner service from 4 to 8 pm generates essentially no solar offset during that window. The peak demand that drives the demand charge is happening at night from the solar system's perspective.

Even for businesses with daytime peaks, solar cannot guarantee demand charge reduction. Here is why: if a 30 kW solar system is running at 25 kW of output when an HVAC unit cycles on and briefly spikes the facility demand to 60 kW, the grid still sees a 35 kW demand event (60 kW load minus 25 kW solar). That 35 kW demand reading still generates a substantial demand charge. Solar reduced the net demand, but it did not eliminate it, and more importantly, it cannot be controlled to precisely cap the demand when a spike occurs.

The fundamental problem is that solar output is determined by the sun. Demand charges are determined by your load behavior at specific moments. Solar cannot be dispatched on demand to smooth out spikes or cover evening peak hours.

Battery Storage as the Demand Charge Solution: Peak Shaving

Battery storage solves what solar cannot. A commercial battery energy storage system (BESS) can be programmed to monitor the facility's real-time power draw and discharge automatically whenever consumption approaches a preset demand threshold - a capability called peak shaving.

Here is how it works in practice. You set a demand cap - say 35 kW. The battery management system monitors consumption continuously. When a load event pushes the facility toward 35 kW, the battery begins discharging to cover the excess. From SCE's perspective, the meter never sees more than 35 kW. Your on-peak demand charge that month is calculated on 35 kW rather than whatever actual peak the facility would have hit.

The battery charges during off-peak hours when both solar production is available and grid energy costs are lower. It discharges during on-peak windows and during demand spike events. This dual function - storing cheap energy and preventing expensive demand peaks - is where the economic value of commercial battery storage is concentrated.

Modern commercial battery systems from manufacturers like Tesla, Fluence, and Powin include demand management software with configurable peak shaving thresholds. The system can track monthly peak demand in real time and automatically protect the demand threshold for the rest of the billing period once a monthly high is recorded.

Real Example: A Temecula Restaurant on TOU-GS-2

Consider a full-service restaurant in Temecula with 3,500 square feet of dining and kitchen space. The business runs lunch and dinner service, with peak kitchen and HVAC loads during dinner from 4 to 9 pm on weekdays. Current monthly electricity profile:

In this example, demand charges ($1,404/month combined) represent 44% of the total bill. A solar-only system sized at 40 kW would offset the energy charges during daytime hours but have minimal impact on the dinner-service demand peak. The bill savings from solar alone might be $600 to $800/month - real money, but demand charges remain largely intact.

Now add a 100 kWh battery system with peak shaving configured to a 30 kW demand cap. The battery charges during lunch hours when solar is producing and the kitchen load is lower. From 4 to 9 pm, the battery discharges to prevent the on-peak demand from exceeding 30 kW. Results:

Demand Charge Reduction ROI Calculation

Commercial solar plus storage systems for businesses like the restaurant example above typically fall in the following cost range in 2025-2026:

• 40 kW solar array: $100,000 to $140,000 installed
• 100 kWh commercial battery system: $80,000 to $130,000 installed
• Combined system total: $180,000 to $270,000

Before incentives. Now the tax math:

• Federal ITC (Section 48E): 30% of total installed cost. On a $220,000 system, that is $66,000 in tax credits in year one.
• MACRS 5-year accelerated depreciation: commercial property owners can depreciate the full cost of a solar and battery system over 5 years using MACRS. At a 25% effective tax rate, this adds another $27,500 to $33,750 in first-year tax benefit on a $220,000 system (assuming 50% bonus depreciation).
• California SGIP rebate: covered in the next section.

Net cost after ITC and first-year depreciation benefit on a $220,000 system: approximately $120,000 to $130,000 effective out-of-pocket cost (the tax credits reduce the actual cash outflow when you account for the reduced tax liability).

Annual savings from the combined system: $13,200 in the restaurant example. Simple payback on net cost: approximately 9 to 10 years. With electricity rate escalation (historically 3% to 5% per year for SCE commercial accounts), effective payback shortens to 7 to 8 years, and the system life is 25 to 30 years.

California SGIP Rebate for Commercial Battery Storage

California's Self-Generation Incentive Program (SGIP) provides direct incentive payments for battery storage systems installed by commercial SCE customers. SGIP does not apply to solar panels - only to storage. This makes it specifically relevant to the demand charge use case where storage is the key component.

SGIP incentive levels are tiered and depend on the program step when the application is filed. Current (2025-2026) base incentive rates for commercial storage range from $150 to $400 per kilowatt-hour of installed capacity. For a 100 kWh commercial system, that represents $15,000 to $40,000 in rebates.

SGIP has equity and resiliency tiers that provide higher incentives for customers in high fire-threat districts (which includes parts of Temecula and Murrieta in SCE territory), facilities that serve critical community functions, or businesses in disadvantaged communities as defined by CalEnviroScreen.

Adding a $25,000 SGIP rebate to the restaurant example above brings the effective net cost down further and tightens the payback period to roughly 7 to 8 years before accounting for rate escalation.

Which Temecula Businesses Benefit Most

Not every commercial account on TOU-GS-2 has the same demand charge problem. The businesses that benefit most from solar plus storage for demand charge reduction share a specific load profile: high peak demand relative to average consumption, with peaks concentrated in on-peak hours.

Restaurants with dinner service are consistently among the highest-demand-charge businesses on a per-square-foot basis. Medical offices running imaging equipment, sterilization cycles, and HVAC simultaneously have similarly spiky load profiles. Fitness centers with evening rush hours face peak demand exactly when TOU-GS rates are highest.

Light commercial retail and office spaces with predictable, steady loads are better candidates for solar-only solutions where demand charges are a smaller proportion of the total bill. The analysis always starts with pulling 12 months of interval data from SCE (15-minute intervals) to understand the actual demand profile before sizing any system.

Starting Point: Read Your SCE Bill Correctly

Before calling any solar contractor, pull your last 12 months of SCE bills and find these two numbers: total energy charges (kWh-based) and total demand charges (kW-based). Add them up separately. If your demand charges represent more than 25% of your total annual bill, demand charge management should be the primary focus of any solar plus storage proposal you request.

When requesting proposals from solar contractors for commercial TOU-GS accounts, specifically ask: (1) what is the projected demand charge reduction, (2) what demand cap is the battery sized to protect, and (3) how many hours per day can the battery sustain peak shaving at the proposed threshold before needing to recharge.

A proposal that only shows you kWh offset and does not address demand charges is an incomplete commercial solar analysis. The demand charge piece is often where the difference between a 12-year payback and a 7-year payback lives for high-demand Temecula commercial accounts.