A load study is an engineering assessment that evaluates a site’s existing and forecast electrical demand to determine whether the electrical infrastructure can safely support additional loads—such as EV chargers—without exceeding limits. In EV charging projects, a load study is used to size the grid connection, switchgear, and feeder capacity, and to decide whether controls like load management are required to avoid overloads and reduce upgrade costs.
What Is a Load Study?
A load study analyzes how much power a site uses now and how it is likely to use power after EV chargers are installed. It typically includes:
– Review of existing electrical drawings and connection capacity (transformer, main breaker, feeder ratings)
– Measurement and analysis of current demand (load measurement and load profile)
– Identification of peak demand periods and peak duration
– Evaluation of spare capacity (“headroom”) for EV charging
– Scenario modeling for future growth (more EVs, higher utilization, seasonal changes)
The outcome is a set of recommendations: allowable charger count, required upgrades, and control strategies.
Why Load Studies Matter in EV Charging Infrastructure
EV chargers can add large coincident loads. A load study helps prevent:
– Tripped breakers and overheating cables due to insufficient capacity
– Overbuilding infrastructure (oversized switchgear, unnecessary grid upgrades)
– Underbuilding (too few chargers or poor performance during peak demand)
– Compliance issues with utility connection rules and electrical codes
For multi-tenant sites, a load study also supports transparent decisions about allocation, billing, and upgrade responsibility.
What a Load Study Typically Includes
A load study for EV charging commonly covers:
– Site supply details: single-phase vs three-phase, line-to-line voltage, earthing system
– Main protection and capacity limits (fuse sizes, contracted demand, transformer rating)
– Existing building loads and their duty cycles (HVAC, production, kitchens, lifts)
– Demand data analysis (15-min or 1-hour intervals over weeks/months)
– Voltage drop checks and feeder/cable sizing considerations
– Charger placement plan and diversity assumptions (how many charge simultaneously)
– Recommendations for load balancing, load curtailment, or scheduling
How Load Studies Are Performed
A typical process looks like:
– Collect utility bills and interval data to understand historic peaks
– Install temporary meters/CTs if detailed data is missing
– Build a baseline load profile and identify worst-case conditions
– Model EV charging demand scenarios (e.g., 10 × 11 kW, 20 × 22 kW, fleet overnight clustering)
– Evaluate compliance against site limits and protection coordination
– Propose an optimized design (infrastructure sizing + control strategy)
The more real data used, the less the study relies on conservative assumptions.
Load Study Outputs for EV Charging Projects
Common deliverables include:
– Maximum safe EV charging capacity (kW) within the existing connection
– Recommended number and power rating of chargers (e.g., 11 kW vs 22 kW AC)
– Whether a grid upgrade is required, and what size
– Control strategy recommendation (static vs dynamic load management)
– Electrical design notes: distribution board capacity, phase allocation, cable routes
– Risk notes: seasonal peaks, future tenant growth, contingency margins
Practical Considerations and Common Pitfalls
Load studies can be misleading if assumptions are unrealistic:
– Using too short a measurement period that misses seasonal peaks
– Ignoring future growth in building load or EV adoption
– Assuming all chargers run at full power continuously (overly conservative)
– Not accounting for minimum current limits and user experience under load control
– Missing phase constraints and phase imbalance risks in three-phase sites
A good load study balances safety margins with realistic diversity and operational behavior.
Related Glossary Terms
Load profile
Load measurement
Load profiling
Load management
Load balancing
Site power limit
Phase balancing
Voltage drop
Demand response
Peak shaving