Residential level 2 charging service


EVs are becoming popular.  For people with garages, charging them is easy.  However, many people in cities don't have garages or dedicated parking spots and will find charging to be inconvenient.  Public level 2 chargers are few and slow.  This note describes a way to profit from this situation by providing neighboring city dwellers a convenient charging service.  It assumes that a person lives in the city and has at least one parking space available to customers.

The concept is

1.       Wire the parking spaces for level 2 charging (240Vac, 50A).  Set up hardware to control and measure charging current.  See fig 1.  Everything is controlled by software on the computer.

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

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

4.       All aspects of the operation, including enrolling, can be automated.

5.       An app will be available to enrolled customers to schedule charging, view status and receive alerts.  It will also help authenticate the customers.

Besides cars, there will soon be a large number of electric scooters and motorcycles.  These will require the same charging infrastructure.




6AWG Cable + installation cost

$25 / foot

25 feet of cable


Parts cost


Typical total cost

$600  (not including a charger)

Rebate Programs

Up to $3,000 per plug

Installation cost (after rebate)


Per Session

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 + 9.00 = $23.00




Expected number of customers

4 to 8

Expected charges per week

5 to 8

Expected charges per year

250 to 400

Average profit per year per space

$3,500 to $5,200

Parts needed

A few parts 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


A charger plugs into the 240Vac NEMA socket and has an EV connector at the other end.  Though the charger is mostly a power switch, it costs around $500 to $700.  This part is deliberately omitted for the following reasons:

·         Each EV owner can bring their own charger.  EV manufacturers include a mobile charger with each vehicle.  If the owner does not have their own charging spot, then this charger would likely be in the vehicle.

·         There are multiple standards for the charger connector.  The connector used by a Tesla is different from the J1722  that used by Ford.

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

Note that the charger would be effectively free after rebates and can be included in the cost of parts if desired.


·         Management server.  Can be a Pi, or a PC

·         May also need a Pi acting as a Bluetooth sensor near charge port.

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 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

Billing functions

·         Charge customer credit card for usage

·         Allow for refunds, if necessary

·         Validate credit card on enrollment

·         Monthly billing

·         Enroll new customer

o   name, address

o   Charging activation fee

o   Markup

o   charging schedule

o   credit card

o   vehicle model & license plate

o   Bluetooth MAC for Teslas

·         Review customer usage patterns


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 chargers.  It would be best to keep the equipment concealed and not advertize their presence.

Chargers are usually not locked in place.  If customers are made to bring their own chargers or adapters, they risk having their equipment stolen.  It may be necessary to provide a physically locked enclosure for the chargers.



After the profitability of this concept has been validated, the software 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.