As EV Parking Share Keeps Rising, How Many Mobile EV Chargers Should a Parking Lot Pilot?

A 500-space parking facility has 40 electric vehicles today. Should the operator build 10 fixed charging bays, 20, or 50? If too many are installed, capital is committed before utilization exists. If too few are installed, the site may face queues, repeat construction and customer complaints as EV adoption rises. The harder problem is not whether charging demand will grow; it is how to size infrastructure while that demand is still uncertain.

This is where a Mobile EV Charger can be evaluated as pilot infrastructure rather than simply as another charger. Instead of permanently tying every charging service to a dedicated bay, a mobile energy asset can be dispatched to parked vehicles as requests appear. For operators, that creates an opportunity to measure actual charging behavior before committing to a much larger fixed build-out.

Door Energy develops and manufactures mobile charging and energy-storage charging systems for commercial, rescue and industrial applications. For parking facilities, its MCP-D autonomous charging robot is designed to move within a controlled parking environment, receive charging tasks, travel to a target vehicle and deliver energy at the parking space. Visit the Door Energy website or review the MCP-D autonomous charging robot for current product information.

I. EV Share Is Rising, but the Real Parking-Lot Question Is Capacity Risk

Why EV growth matters to parking operators

Global electric-car adoption continues to change the vehicle mix entering offices, shopping centers, airports, hotels, hospitals and public garages. According to the International Energy Agency (IEA), electric-car sales exceeded 20 million worldwide in 2025 and represented about 25% of global new-car sales. The IEA also estimates that the global electric light-duty vehicle stock reached roughly 76 million in 2025, while public charging points exceeded 7 million.

However, national EV sales share is not the same as the EV share in one parking facility. A downtown office garage may have a very different vehicle profile from an airport long-stay lot or a suburban shopping center. Therefore, the first planning mistake is to use a national EV percentage as if it were a site demand forecast.

The first four numbers a customer should measure

Before purchasing equipment, a parking operator should collect at least 30 to 60 days of site data. The goal is to separate “EVs that are present” from “EVs that actually request energy.” Those are not the same population.

• Daily parked vehicles or daily vehicle entries.
• EV share during normal and peak periods.
• Charging request rate: the percentage of parked EVs that actually ask for charging.
• Average energy requested per charging session, measured in kWh.

For example, a 300-space office facility might see 500 vehicle entries per day, including 50 EVs. If only 15 drivers request charging, the relevant service demand is 15 charging tasks—not 50 theoretical EV customers. This distinction prevents a facility from overbuilding based on vehicle presence alone.

II. Why “Just Install More Fixed Chargers” Is Not Always the Best First Step

The hidden operational cost of a charger tied to a parking bay

Fixed chargers are essential infrastructure and will remain the right foundation for many locations. The problem appears when a facility tries to solve every future charging requirement with fixed bays before it understands where, when and how often charging demand will occur.

A fixed charging space creates a physical relationship between one charger and one parking location. When demand is low, that space may be underused. When demand is high, a driver may need to move the vehicle after charging so another user can access the charger. At workplace sites, the U.S. Department of Energy specifically notes that shared charging may require reservation systems, idle-fee policies or even midday vehicle movement when one charger must support multiple sessions.

The most useful way to position Door Energy in this context is not “mobile replaces fixed.” A more credible architecture is Fixed Charging + Mobile Capacity + Intelligent Scheduling. Stable, predictable demand can be served by fixed infrastructure, while mobile capacity helps with pilot programs, changing demand, peak periods and areas where a full electrical retrofit is difficult.

The industry pain point is not only charging—it is forecasting

Suppose a 500-space property has 40 EVs on a typical busy day. In two years, the same site could have 50 EVs, 75 EVs or 125 EVs. Building for the highest scenario today may create years of underutilized capital. Building only for current demand may cause a second construction cycle later. Doing nothing may reduce tenant or customer satisfaction. A mobile pilot gives the operator a fourth option: measure first, then scale with evidence.

III. Before Choosing the Number of Mobile EV Chargers, Calculate These Four Numbers

1. Daily charging requests

If a facility receives 600 vehicles per day, 10% are EVs and 30% of those EVs request charging, expected demand is about 18 charging tasks per day. That is a much stronger planning input than saying “the parking lot has 600 cars.”

2. Average kWh per session

Parking customers do not normally arrive at 0% state of charge and demand a full battery. In a review of about 150,000 workplace charging sessions across five U.S. federal campuses, the U.S. Department of Energy reported an average of approximately 15 kWh per vehicle charging session. That number should not be treated as a universal parking-lot average, but it is a useful external benchmark for building a pilot scenario.

Using the earlier example, 18 sessions × 15 kWh equals approximately 270 kWh of daily requested energy. The customer is no longer asking only “How many chargers?” The better question becomes “How many charging tasks and how many kWh must the system reliably deliver during the operating window?”

3. Peak-hour concurrency

Eighteen requests spread across twelve hours are easier to serve than eighteen requests concentrated between 8:30 a.m. and 10:30 a.m. Therefore, operators should record not only daily volume but also the busiest one-hour and two-hour windows. Peak concurrency determines whether a single mobile unit can sequence tasks or whether two units are required to operate in parallel.

4. Service-cycle time

A charging task includes more than electrical charging time. The full service cycle may include dispatch, travel through the garage, positioning, connection, charging, disconnection, travel to the next vehicle and—in some cases—the Mobile EV Charger returning for its own replenishment. A pilot should measure the whole cycle, because this determines tasks per day.

IV. How Many Units Should a 100-, 300-, 500- or 1,000-Space Parking Lot Pilot?

Use parking-space count as a starting point—not the final answer

When a facility has no historical charging data, parking-space count can still be used to establish a first pilot range. However, it must be adjusted with EV share, request rate, energy demand and peak concurrency. The following table is a pilot-planning model, not a universal engineering standard or regulatory requirement.

For many 100- to 200-space properties with low-to-moderate EV share, one unit can be enough to answer the first question: will customers actually use a mobile charging service? At 300 to 500 spaces, two units often create a more informative pilot because the operator can test simultaneous demand, task prioritization and what happens while one unit is recharging or unavailable.

A 200-space example

Assume 200 occupied spaces at peak, an 8% EV share and a 30% charging request rate. That produces roughly five charging requests. If the average energy requirement is 15 kWh, daily requested energy is about 75 kWh. In this scenario, one unit can be a reasonable demand-validation pilot, subject to actual service timing and reserve-energy requirements.

A 500-space example

Assume 500 occupied spaces, a 12% EV share and a 35% request rate. That produces approximately 21 charging requests. At 15 kWh per session, the daily energy requirement is about 315 kWh. This immediately shows why a 105 kWh mobile battery cannot be evaluated by nameplate capacity alone; the operator must model replenishment cycles, usable state-of-charge window, conversion losses, vehicle acceptance rate and scheduling. A two-unit pilot may be appropriate for dispatch testing, but commercial fleet sizing should be based on measured throughput.

Why one unit, two units and three units answer different questions

In other words, the first unit validates demand, the second validates concurrency and dispatch, and additional units move the project toward fleet-scale operations. This staged approach gives facility managers a clearer basis for capital approval than guessing the final charger count on day one.

V. How Door Energy Turns Charging from a Parking-Space Problem into a Dispatching Problem

The MCP-D workflow in a controlled parking facility

Door Energy’s MCP-D is built around a simple operational idea: the vehicle can remain in its parking space while the charging asset is dispatched to it. This changes the workflow from “driver searches for an available charger” to “system schedules energy delivery.”

Step 1 — Charging Request: When a vehicle needs energy, the driver or facility platform sends a charging request.

Step 2 — Vehicle Location: The scheduling system identifies the parking position using the facility map and available sensing or positioning information.

Step 3 — Autonomous Movement: The unit travels through the parking environment toward the target vehicle.

Step 4 — Charging: Connection can be completed according to the project design, followed by controlled DC charging.

Step 5 — Task Completion: After charging, the unit can accept another task or return to its designated standby/replenishment point.

For a dedicated project example, see Door Energy’s MCP-D Autonomous Charging for Parking Facilities case. The broader Mobile EV Charger product range also includes mobile energy-storage configurations for roadside rescue, heavy vehicles and industrial use.

What the MCP-D specifications mean for the customer

The distinction between kW and kWh is especially important. Charging power in kW describes how fast energy can be transferred under appropriate conditions. Battery capacity in kWh describes how much energy is stored. A 100 kW output rating does not mean the unit can continuously charge vehicles at 100 kW all day without replenishment. Therefore, buyers should evaluate both energy capacity and service-cycle throughput.

Match every product feature to a parking-lot pain point

Door Energy’s broader product portfolio extends beyond parking facilities. Depending on product configuration, its mobile systems are designed for roadside EV rescue, heavy commercial vehicles and industrial power applications. The company publishes solutions supporting up to 420 kW DC output for high-power mobile charging, with CCS1/CCS2 and OCPP support, while energy-storage systems can also support AC loads such as electric construction equipment, pumps and lighting. This matters to fleet or energy-service customers that want mobile assets capable of serving more than one business model.

For more information about the manufacturer, R&D and production capabilities, see About Door Energy. For common technical and service questions, see the Door Energy FAQ.

VI. When Should the Parking Lot Add a Second or Third Unit?

Do not scale from EV share alone

A parking operator should not automatically add another Mobile EV Charger simply because EV share crosses a single percentage threshold. The stronger trigger is operational stress: increasing waiting time, unserved requests, repeated concurrency, insufficient daily energy throughput or recharge downtime that interferes with customer service.

A useful expansion rule is to require more than one signal. For example, if utilization is high but there are no queues and all requests are completed within the promised service window, immediate expansion may not be necessary. However, if high utilization occurs together with rising wait time and recurring unserved requests, adding capacity becomes easier to justify.

A practical 60- to 90-day pilot scorecard

• EV share by day, weekday/weekend and parking zone.
• Charging requests per day and per peak hour.
• Average and median kWh delivered per session.
• Average response time from request to arrival.
• Average end-to-end service-cycle time.
• Percentage of requests completed within the target service level.
• Number of unserved or cancelled requests.
• Energy used by the mobile unit itself and number of replenishment cycles.
• Customer repeat-use rate and satisfaction feedback.
• Maintenance events and service downtime.

After the pilot, the operator can decide whether to add another mobile unit, install more fixed charging, combine both approaches, or change the service model. That is the strategic value of pilot infrastructure: the next capital decision is based on observed behavior rather than assumptions.

Who should own the pilot data?

The most successful pilot is not owned by the charging supplier alone. Facility management should track parking patterns and customer complaints; the electrical or engineering team should monitor available power and replenishment constraints; the charging operator should monitor sessions, kWh, response time and failed tasks; and property management should evaluate whether the service improves tenant or visitor experience. Bringing these records together prevents a common mistake: judging the pilot only by the number of charging sessions. A low session count may indicate weak demand, but it may also reflect poor user awareness, inconvenient request workflows or restricted operating hours. Door Energy customers should therefore define the measurement plan before deployment, not after the first month of operation.

FAQ: Planning a Mobile Charging Pilot for Parking Facilities

How many units should a 100-space parking lot start with?

If EV share and charging demand are still low or uncertain, one unit is often enough for a first pilot. The objective is to measure request volume, average kWh, service-cycle time and customer acceptance before adding capacity.

How many units should a 300-space parking lot use?

For a site with modest EV demand, one unit may still be sufficient to validate the concept. If simultaneous requests already occur, two units provide a better test of concurrency, scheduling and replenishment downtime.

Does a 500-space parking lot automatically need five mobile chargers?

No. Parking-space count alone is not a sizing formula. A 500-space facility should calculate EV share, charging request rate, average kWh per session, peak-hour demand and full service-cycle time before deciding the fleet size.

Can a Mobile EV Charger replace all fixed chargers?

Usually, that is not the best planning assumption. Fixed chargers are efficient for stable, predictable demand. Mobile charging is especially valuable for pilot programs, variable demand, peak support and locations where electrical upgrades or dedicated charging bays are difficult. A hybrid model can use both.

Why is autonomous charging useful in a parking facility?

Vehicles are stationary, locations are known, and parking duration often exceeds the time needed to deliver a useful amount of energy. Instead of asking the driver to move to a charging bay, the energy asset can be scheduled toward the vehicle.

What is the difference between 100 kW and 105 kWh on the MCP-D?

The 100 kW figure describes the unit’s published maximum charging power, while 105 kWh describes its battery energy capacity. Power affects charging speed; energy capacity affects how much energy is available before replenishment. Both must be modeled.

How many vehicles can one MCP-D charge per day?

There is no single correct number. It depends on kWh requested per vehicle, actual vehicle acceptance power, travel time, connection time, usable state-of-charge window, replenishment strategy and peak concentration. That is exactly why a pilot should measure sessions per day and kWh delivered per day.

Which charging standards does Door Energy support for MCP-D?

The current MCP-D product page lists CCS1 and CCS2 charging interfaces and OCPP 1.6J communication. Final connector and system configuration should be confirmed for the target vehicle population and region.

What should trigger the purchase of a second unit?

Frequent concurrent requests, rising response time, recurring unserved tasks, high practical energy throughput and replenishment downtime that disrupts service are stronger triggers than EV percentage alone.

Is the system suitable for underground or multi-level parking?

The published MCP-D specifications include L4 autonomous driving, a maximum speed of 10 km/h and gradeability above 20%. However, every project still requires a site assessment covering ramp geometry, turning radius, pedestrian routes, barriers, communications and the replenishment point.

What if the parking lot already has fixed chargers?

That can be an ideal pilot environment. The operator can use fixed chargers for predictable base demand and Door Energy mobile capacity for overflow, remote bays, peak periods or customers who cannot access a fixed charger.

Why choose Door Energy for a pilot?

Door Energy combines mobile energy storage, EV charging, autonomous parking-facility solutions and broader commercial/industrial charging experience. Its portfolio includes parking, roadside rescue and industrial mobile-energy configurations, while modular design and platform integration can support long-term operational planning.

Conclusion: Start Small, Measure Real Demand, Then Scale

The central planning question for a parking facility is no longer simply “How many charging bays should we install?” A more useful question is: “How many charging tasks will we receive, how much energy will customers request, and how concentrated will those requests be?”

That shift changes infrastructure planning. A 100- to 200-space facility may be able to begin with one Mobile EV Charger when demand is still uncertain. A 300- to 500-space location with existing concurrency may learn more from a two-unit pilot. Larger facilities should move away from space-count ratios and size a mobile fleet from measured charging requests, daily kWh, service-cycle time, peak concurrency and customer service targets.

Door Energy’s MCP-D is designed around this operating model: receive a task, locate the vehicle, move through the parking facility, deliver charging and return to the next task or replenishment point. Its 105 kWh energy storage, up to 100 kW published charging output, CCS1/CCS2 support, OCPP 1.6J communication and autonomous movement capabilities make it relevant to facilities that want charging capacity to follow parking demand rather than remain permanently attached to every charging bay.

More importantly, a pilot turns uncertainty into operating data. Instead of forecasting five years of EV behavior on day one, the operator can measure demand, validate customer acceptance and expand only when the data supports the next investment. For parking operators, property managers and charging service providers, that is the real business value: not simply adding another charger, but building a charging system that can scale with the EV population.

Explore Door Energy mobile charging solutions, review the MCP-D product page, or visit Door Energy to discuss a parking-facility pilot based on your parking capacity, EV share, traffic pattern and target service level.

Sources and Data Notes

External market figures are used to establish context and should not be treated as site-specific demand forecasts. Pilot sizing ranges in this article are planning examples, not universal standards.