Charging utilization measures how much of the time chargers are actually delivering energy, distinct from how often the charging spaces are occupied. In a parking facility:
- The gap between occupied and charging is large at long-stay sites. In University of California Institute of Transportation Studies research at San José Mineta International Airport, 42.2 percent of charging sessions at one lot showed a 3:1 ratio of time occupying the charger to time actively charging: full-looking spaces, nearly idle assets.
One 150 kW DC fast charger, installed for about $140,000. Set how often drivers use it, what they pay and the utility rate, and see the monthly result and the payback.
At 8 sessions a day and $0.50 per kWh, a fast charger on a utility rate with a $15 per kW demand charge loses money: the $2,250 monthly demand charge outweighs the energy margin. On an EV rate without a demand charge, the same charger nets about $1,850 a month and pays back in a little over 6 years. Utilization and the utility rate decide the case more than the price per kWh.
Illustrative: 30 kWh a session, $0.18 per kWh energy cost, $15 per kW demand charge on 150 kW, $300 a month for network and maintenance, 5% payment fees, $140,000 installed cost before incentives. Rates and costs vary widely by utility and site.
Considerations
- Low utilization signals over-speeding or over-counting, not success. Measure energy delivered, not stalls occupied.