Every weekday between 4 PM and 9 PM, California's electricity grid enters its most expensive window. The three investor-owned utilities charge commercial customers two to three times more per kilowatt-hour during these peak hours compared to off-peak periods. For a typical 100,000 square foot commercial building consuming 2,000 kWh during the five-hour peak window, the daily cost difference between peak and off-peak pricing can exceed $350. Over a full summer season, that adds up to more than $25,000 in avoidable expense for a single building.
Peak load shifting is the practice of moving electricity consumption away from high-cost periods into lower-cost ones without sacrificing building performance or occupant comfort. Unlike energy conservation, which aims to reduce total consumption, load shifting focuses on when energy is consumed rather than how much. A building that uses the same total kWh but shifts 20 percent of that usage from peak to off-peak can reduce its annual electricity bill by 8 to 12 percent with no reduction in service quality.
This article outlines the specific strategies that California commercial building operators are using to shift load away from the 4-to-9 PM peak window. These strategies range from zero-cost BMS programming changes to capital investments in battery storage, with each approach sized and evaluated based on the actual rate differentials charged by PG&E, SCE, and SDG&E.
The Economics of Peak Avoidance
To understand why load shifting matters in California more than almost any other state, you need to look at the actual rate spreads. Under PG&E's B-20 schedule, summer peak energy charges reach approximately 49.9 cents per kWh compared to 31.4 cents off-peak, a spread of 18.5 cents. SCE's TOU-8 schedule shows a similar differential of 15 to 20 cents per kWh. SDG&E, with historically the highest rates in the state, can show spreads exceeding 22 cents per kWh during summer months.
These energy charge differentials are only part of the picture. Demand charges add another layer of savings potential. Under most California commercial TOU schedules, the demand charge applied during peak hours is two to four dollars higher per kW than the off-peak demand charge. A building that reduces its peak-period demand by 100 kW saves an additional $200 to $400 per month in demand charges on top of the energy savings.
The combined impact of energy and demand savings makes California one of the most attractive markets in the country for load-shifting investments. A building that successfully shifts 150 kW of load from peak to off-peak during the summer can save $3,000 to $5,000 per month, or $15,000 to $25,000 over a five-month summer season. For a portfolio of ten similar buildings, the annual savings potential reaches $150,000 to $250,000.
Pre-Cooling: The Highest-Impact Zero-Cost Strategy
Pre-cooling is the practice of lowering a building's temperature before the peak pricing period begins, effectively storing coolness in the building's thermal mass. The concrete, steel, and furnishings in a commercial building can absorb and hold a significant amount of cooling energy. By dropping the interior temperature by two to four degrees Fahrenheit between 1 PM and 4 PM (during the less expensive mid-peak or off-peak period), you create a thermal reservoir that allows the building to coast through the first two to three hours of peak pricing with minimal HVAC operation.
Implementation Steps
The implementation is straightforward for any building with a programmable BMS. Set the cooling setpoint to 70 or 71 degrees Fahrenheit starting at 1 PM. At 4 PM, raise the setpoint to 76 or 77 degrees. The HVAC system will essentially stop running as the building gradually warms from 71 to 76 degrees over the next two to three hours. By 6 PM or 7 PM, occupancy typically drops significantly, further reducing cooling demand for the remainder of the peak period.
The key variables that determine pre-cooling effectiveness are building insulation quality, window-to-wall ratio, solar orientation, and occupancy density. Well-insulated buildings with lower window ratios hold their temperature longer. Buildings with significant west-facing glass will experience faster heat gain during late afternoon and may need more aggressive pre-cooling or supplementary strategies.
Occupant communication is important. Tenants should understand that the building will be slightly cooler in the early afternoon and slightly warmer in the late afternoon. In practice, most occupants find the pre-cooled temperature more comfortable than the typical 74-degree setpoint, and the gradual warming during peak hours is imperceptible if managed properly.
HVAC Staggering and Sequencing
Most commercial buildings have multiple HVAC units or air handling units serving different zones. When peak pricing begins and cooling demand ramps up, these units often start simultaneously, creating a demand spike that sets the peak demand charge for the entire billing period. HVAC staggering is the practice of sequencing unit startups and limiting the number of units running at full capacity simultaneously.
A building with six rooftop units might program them to cycle such that only four are operating at any given time during peak hours. Each unit runs for 40 minutes and pauses for 20 minutes, rotating through the sequence so that cooling is maintained across all zones while peak demand is capped. This approach can reduce peak demand by 25 to 35 percent without meaningfully affecting zone temperatures, because the building thermal mass continues to provide cooling during the brief pause periods.
For buildings with chiller plants, sequencing is even more effective. Rather than running all chillers at partial load (which is inefficient), operators can sequence chillers to run fewer units at higher efficiency during peak hours, relying on chilled water storage or thermal mass to bridge gaps. This approach simultaneously reduces energy consumption and peak demand.
Demand Limiting Controls
Advanced BMS platforms include demand-limiting algorithms that monitor real-time building demand and automatically shed non-critical loads when a preset demand threshold is approached. These systems can be programmed with priority hierarchies: parking garage lighting reduces first, then lobby fountain pumps, then non-essential ventilation, and finally HVAC compressors in unoccupied zones. The result is a hard cap on peak demand that prevents demand charge spikes from isolated events.
Thermal Energy Storage Systems
Thermal energy storage, typically using ice storage or chilled water tanks, takes the pre-cooling concept to an industrial scale. These systems produce ice or chilled water during off-peak hours using cheap electricity and then melt that ice during peak hours to provide cooling without running chillers. The technology has been used in commercial buildings for decades and is well-proven in the California market.
An ice storage system sized for a 200,000 square foot office building typically costs between $300,000 and $600,000 installed, depending on the tonnage required and existing mechanical infrastructure. In a market where the TOU spread is 18 to 22 cents per kWh and the demand charge differential is $3 to $5 per kW, these systems can achieve simple payback periods of four to seven years. When combined with utility incentive programs and demand response revenue, payback can drop to three to five years.
Newer technologies include phase-change materials that can be integrated into building walls, ceilings, and floors. These materials absorb heat as they melt (during warm afternoon hours) and release it as they solidify (during cooler nighttime hours), providing passive thermal storage without dedicated mechanical systems. While still emerging in the commercial market, phase-change materials offer promising economics for new construction and major renovations in California's TOU pricing environment.
EV Charging and Plug Load Management
As California commercial buildings add EV charging infrastructure to comply with the state's green building code and attract tenants, the electrical load from EV chargers is becoming a significant factor in peak demand. A Level 2 charger draws 7 to 19 kW, and a DC fast charger can draw 50 to 150 kW. A parking garage with twenty Level 2 chargers operating simultaneously during peak hours adds 140 to 380 kW of demand, potentially increasing the building's peak demand charge by $400 to $1,500 per month.
Smart EV charging management systems address this by pausing or throttling chargers during peak TOU hours and resuming at full power once the peak period ends at 9 PM. Most EV drivers in a workplace setting do not need their vehicles fully charged by 5 PM, they just need them charged by the next morning. Shifting EV charging to the 9 PM to 6 AM window captures the lowest off-peak rates while completely eliminating the demand impact during peak hours.
Beyond EV chargers, other controllable plug loads include server room cooling (which can be pre-cooled like the rest of the building), kitchen and break room equipment in commercial offices, and irrigation and landscape lighting that can be scheduled entirely outside peak hours. Individually, these loads are small, but across a portfolio of buildings, they add up to meaningful savings.
Measuring Load-Shifting Results
Effective load shifting requires ongoing measurement and adjustment. The primary metrics to track are your peak-period consumption as a percentage of total consumption (target below 25 percent), your peak-period demand in kW relative to your overall maximum demand, and your effective blended rate per kWh calculated from your total bill divided by total consumption.
Pull interval data from your utility monthly and overlay it against the TOU schedule to visualize when consumption is occurring. Look for buildings where the load profile shows a flat or increasing pattern during peak hours, indicating that load shifting strategies are not yet effective. Buildings where the profile clearly dips during the 4-to-9 PM window are performing well.
Across a portfolio, establish benchmarks for peak-period performance and track them monthly. Identify the top-performing and bottom-performing buildings each month. Investigate what the top performers are doing differently and replicate those practices across the portfolio. Over time, this continuous improvement approach drives the entire portfolio toward optimal TOU performance.
A portfolio of California commercial buildings that reduces peak-period consumption from 40 percent to 25 percent of total usage typically saves 10 to 15 percent on annual electricity costs, with the majority of savings concentrated in the June-through-September summer peak season.