Residential level 2 charging service


Electric Vehicles (EVs) are becoming popular.  For people with garages, charging them is easy.  However, many city dwellers don't have garages or dedicated parking spots and will find charging to be inconvenient.  Public level 2 chargers are few and unreliable.  They are slow, typically taking 6 hours to charge.  Level 3 fast chargers can take only 20 mins, but are much fewer and more expensive.  This note describes a way to profit from this situation.  

This note describes a product that enables private entrepreneurs to provide a convenient charging service to EV drivers in cities.  It will also be attractive for housing complexes and small businesses.  Note that we are not offering the charging service, but are enabling others to do so.  The product is not intended for large service providers building a nationwide network of chargers, but for small players who want a quick way to profit in a neighborhood.  It will only support level 2 charging, not fast charging.  The product will be inexpensive and will include the software required.  A key point is that there currently (in 2023) are many government rebate programs that can slash the initial installation cost.  The service provider has to have at least one parking space available for extended periods for customer charging. 

To get started

After obtaining the product, a service provider would:

1.       Install power cables in the parking spaces for level 2 charging (240Vac, 50A) and set up the provided hardware to control the charging, as shown in Fig 1.  Everything is controlled by software on the computers.

2.       Enroll a few customers.  Their credit card will be needed for automatic billing at end of the charging session.

3.       Allocate scheduled slots during the week.  Unscheduled charging will be available when no one else is scheduled.

4.       Customers would use a free app to schedule charging, view status and receive alerts.  It will also authenticate the customer.

5.       All aspects of the operation, including enrolling, would be automated so that the service provider would not be involved for charging sessions.

The Charger Controller authenticates the customer, switches the current supply on or off, measures the charge supplied, and bills the customer.  The outdoor plug point comprises the 240v NEMA plug and an optional computer that can interact with the customer.  The Vehicle Charger adapts the 240v to the specific EV.  This design allows the charge rate to be increased substantially, though the installation cost will also increase. 



6AWG 4 conductor Cable

$8 / foot

25 feet of cable + installation cost


Parts cost for Charger Controller


Parts cost for Outdoor Plug point


Software for Controller & Plug point


Typical total cost for first plug

500 + 100 + 100 + 1000= $1,700

Cost for additional plugs

100 + 100 = $200

Vehicle charger (optional, see below)

$500 (not included in costs above)

Rebate Programs (may expire)

$3,500/plug or 60% of project cost

Installation cost (after rebate)


Per Session costs

Average charge / session

 60 kWh

Charge rate


Charge time

 60 / 7 = 9 hours (all day or all night)

Cost of electricity

 ~15 cents/kWh

Charge cost

 60 * 0.15 = $9.00

Charging activation fee

 $5 / session (configurable)

Electricity cost markup

 100%  (configurable)

Cost to customer/session

 $5 + $9.00 * 2 = $23.00



Annual projections

Expected number of customers

4 to 8

Expected charges per week

5 to 20

Expected charges per year

250 to 1000

Annual insurance & maintenance costs


Average profit per year per plug

$3,500 to $14,000


For a homeowner who can spare a couple of parking spots on their driveway, this provides a nice annual income with minimal effort.  Apartment complexes that offer 8 charging spots per 100 homes would greatly increase their housing value.  Businesses like grocery stores and malls can dedicate a few of their parking spots for charging, though it may be inconvenient for drivers to charge their cars at these remote locations.

Besides cars, there will soon be a large number of electric scooters and motorcycles.  These will require the same charging infrastructure.  Thinking ahead, it would be good to support the charging of multiple scooters simultaneously.


1.      In today's cities, vandalism is the main risk.  Any loose charging equipment is likely to be stolen.  Besides theft, there are miscreants who would find it amusing to damage the installation.  It would be best to keep the equipment concealed and not advertize their presence.  The design keeps most of the sensitive parts indoors.  The outdoor parts are limited to the NEMA power socket, an inexpensive computer that supports Bluetooth and an optional display.

2.      Vehicle chargers are usually not locked in place.  If customers are asked to bring their own vehicle charger and adapters, they risk having their equipment stolen.  It may be necessary to provide a physically secured enclosure for these chargers.

3.      A camera would be a recommended best practice.  More importantly, there should also be signs saying that a camera is rolling.  The camera would also be useful to sense the presence of a vehicle in the charging space. 

4.      Insurance would be needed in most city areas.

Business Plan

After the profitability of this concept has been validated, the product can be sold to other city dwellers who have parking spaces.  The app could reserve charging slots across different charging sites.  There are several state & federal government rebate programs that will cover the cost of installation.

Destination stations in small hotels and Bed & Breakfasts could also use this model.

Parts needed

A few parts for the Charger Controller are listed just to demonstrate the validity of the installation cost.

Power meter

AC Current Voltage Power Energy Frequency Power Factor Communication Module Meter 100A Ammeter Voltmeter Multimeter with RS485 USB Interface and Split Core Current 

·         May need 2, one for each phase

·         $21 Amazon


TWTADE/JQX-62F-2Z Coil Voltage AC 110V 80A DPDT Electronmagnetic Relay,High Power Relay AC 110V

·         Double pole

·         This needs a 5 Vdc relay to drive it with 110V

·         $30 Amazon

Artshu Single Phase Solid State Relay SSR-50DA-H 50A SSR 50DA H DC to AC Relay Solid State Resistance Regulator 

·         Need 2, one for each phase

·         Will get hot

·         $11.49 Amazon

Vehicle charger

A vehicle charger plugs into the 240Vac NEMA socket and has an EV connector at the other end.  It costs between $300 to $700.  This part need not be purchased by the service provider for the following reasons:

·         An EV charger can be specific to each EV model.  There are multiple standards and each standard has a different connector.  For example, the Mobile Connector used by a Tesla is different from J1722/CCS used by most other vehicles.  The Nissan Leaf uses a yet another plug called CHAdeMO.

·         The vehicle charger and adapter can be stolen by vandals or damaged by careless users.

The service provider could optionally install a J1722/CCS connector with an adapter for Teslas.


·         Management server.  Can be a PC or a Pi.  It would have a web server to allow browsers to add new accounts, print reports, etc.

·         There would also be a separate Raspberry Pi acting as a Bluetooth sensor near each charge point.

Software: Management server

Web functions

·         Validate customer to start charging.  Customer should click to approve a charging session. App can use GPS to validate location.  If location is more than 100 meters away, then need to click 'confirm'.  App can be optional for Teslas.

·         Notify customer on charge completion, problems, optionally on start

·         Current customer can get charging status: kWh delivered, time till complete, charging problems

·         Charger spot availability status, also when current customer will be done, time till next customer

Power management functions

·         Start & stop charging

·         Monitor charging and stop if some parameter is exceeded

·         A small display will show charging status, though this can also be seen via the app

Idle Time

Customers are expected to vacate the parking space promptly at the end of their slot.  A courtesy period of “idle time” will be allowed, but a hefty fine will be imposed after that.  The customer contract should state that cars may be towed away if the courtesy period is exceeded.

Billing functions

·         Enroll new customer

o   name, address

o   Charging activation fee (typically $5.00)

o   Markup  (typically 100%)

o   Idle time

§  Grace allowance (typically 60 mins)

§  Initial fine ($10.00)

§  Additional fine rate ($0.50/minute, $1.00/min if another customer is affected)

o   Initial charging schedule

o   credit card details

o   vehicle model & license plate

o   Bluetooth MAC (typically for Teslas)

·         Validate credit card on enrollment

·         Charge customer credit card for usage

·         Allow for refunds, if necessary

·         Monthly billing

·         Review customer usage patterns