January 31, 2023

The Importance of Load Calculations When Installing an EV Charger


5 Min. Read

At-home charging remains the most convenient solution for owners of electric vehicles (EVs) as it allows you to charge your electric car overnight, avoiding long waits for public charging, and saving money by charging when utility prices are lower. Upgrading your home’s electrical system to support a Level 2 EV charging station, regardless of the project scope, requires disciplined planning and an expert with specific training in electrical work and EV charger safety requirements, such as load calculations.

Doing a proper job of load calculations is a key success factor for EV charger installations. If not done correctly, the likelihood of EV charging station failures, damage to your home’s electrical system or EV, and even injury, increases exponentially. Repairing damages from improper electrical work can be costly and time-consuming so doing it right the first time with save you money and effort.

To get the best result and ensure safety, follow the guidelines covered in this article.

Volts, Amps, Watts: The Basics of Electricity

Electricity is much like water in that it flows through a conductor from the source to the terminal device. In the case of water, a hose or pipe is typically the conductor and similarly, with electricity, the electrons flow through wires made out of material such as copper or aluminum.

The speed of water flowing through a hose or pipe is measured in gallons per minute, while pressure in the hose or pipe is measured in pounds per square inch (PSI). The speed of electrons flowing through a wire is measured by volts (V) for electricity and the pressure, or force, is measured with amps (A).

Consumption of electricity by a given device (watts) is measured by multiplying amps by volts, or W=(A*V).

The levels of electricity used by EV charging stations can be dangerous if improperly handled or if the materials are not graded for consistent and high levels of energy. While utilizing a formula to calculate a load is beneficial, electrical work of this nature should always be performed by a licensed electrician who has the training and skills necessary to complete the project safely and efficiently.

What This Means to Your Home

Because electrons travel farther and faster at higher voltage, utilities transmit electricity to your home at extremely high voltage. Before it reaches your home, however, the electricity is reduced to a lower voltage by an external transformer and then connected to your home electrical panel.

Although the electricity in your home is at a much lower level of voltage, it is still dangerous and should be treated with caution.

Your electric panel contains circuits connected by wires from the utility service. Depending on the electrical panel’s capacity in amps, a panel can contain a range of circuits with varying amperage capacities. Each circuit has a breaker that trips and essentially cuts the power off when the amperage to that circuit exceeds its capacity.

Electrical panels come in various capacities, for example, 60, 100, 200, or 400 amps.

Implications for Installing a Level 2 EV Charging Station

Level 2 charging stations have specific electric power requirements. Depending on manufacturer requirements, EV chargers generally require between 32 and 80 amps and a 240-volt service. A 60-amp panel will typically be too small to handle this additional charging load. A 100-amp panel may be sufficient for managing the loads, and a 200-amp panel is ideal.

As mentioned, when upgrading your home with a Level 2 charger, you must determine whether your current panel can handle the additional load. If not, you will need to determine with your electrician whether a panel upgrade or a load-shedding solution suits your situation and personal needs the best. One example of a load-shedding solution is a load controller. These devices attach to selected circuits in the panel and trip the breaker when the current exceeds pre-set limits.

Smart panels are a more sophisticated and expensive solution to manage loads, and if you’re considering adding additional electrification technologies to your home, are worth examining.

Most importantly, you must determine if the home has enough overall capacity for the new Level 2 charger to function safely and properly. Otherwise, you risk system failure or even fire damage to your home due to an overload situation. On top of that, the cost of correcting and redoing the work will be substantial.

Measuring Overall Household Capacity-Load Calculations

To determine the total wattage consumption in the house, you will need to perform a comprehensive review and load calculation for your household by adding up the wattage of different appliances and systems. The amperage of the new Level 2 EV charging station will need to be added to the load calculation, ensuring it will not cause the energy draw to exceed the electric panel’s capacity. This is something your electrician should always complete before installing an EV charger, or other large electric appliance, in your home.

A standard Level 2 charging station typically adds approximately 7,200 watts or 30 amps. The additional load may vary depending on the EV model, EVSE model, and usage.

There are a couple of ways to estimate the wattage consumption. One method is to use a load calculation worksheet to record estimated wattages. Another, more precise method is to measure and record each circuit’s wattage utilizing a multimeter to determine these values.

Safety First

Estimating load using a load calculation worksheet requires experience and knowledge of proper methodology. Remember: you want it done right, the first time.

Going into the electric panel to assess and measure circuit loads exposes you to high-voltage wires and accidents can be deadly. If you do not have experience with high-voltage work, it is best to hire a licensed electrician to do the load calculations accurately and safely. In addition, a certified electrician can recommend the best solution for your home needs.

Reaching out for experienced, trained professional help is smart.

Plan Your Charging Space for Maximum Efficiency

Take the time to plan out your charging space to accommodate your things like cables and parts.

The location of car charging ports varies, so check with your manufacturer. Ensure cables are long enough to reach your EV and are placed for easy connection. To preserve and maintain optimal EVSE performance, consider installing a mounted location to keep your charger off the ground.

A well-organized and intentionally designed charging station location will provide greater convenience in charging and maintaining your EV.

Next Steps

Now that you have decided to avoid dependence on public charging and install an at-home EV charging station, you need to start planning for the installation.

To do it right and get the best possible result safely, reach out for expert help.

Qmerit Has the Solutions

Qmerit works with an unsurpassed network of highly qualified and licensed electrification professionals specializing in EV charging technologies and, with over 261,500 completed EV charger installations in the U.S. and Canada, is the most trusted installer of electrification solutions in North America.

If you’re looking for a safe and simplified EV charging station installation with a company you can trust and a peace-of-mind guarantee, contact Qmerit today.

Author: Greg Sowder

Greg Sowder

President, Qmerit Network