Inspect the Existing Electrical System

A professional panel installation should begin with an evaluation—not with removing equipment.

The electrician first needs to understand the existing system.

That can include looking at:

• Current service size
• Existing panel condition
• Breaker configuration
• Number of circuits
• Available panel space
• Grounding and bonding
• Service equipment
• Existing major electrical loads
• Signs of overheating or corrosion
• Previous electrical modifications

The electrician should also discuss what you plan to add in the future.

For example, are you considering an EV charger, solar panels, battery storage, heat pump, electric water heater, kitchen remodel, pool, spa, ADU or home addition?

Those plans can affect how the electrical system should be designed.

Determine the Home's Electrical Load

One of the most important parts of planning an electrical panel upgrade is determining how much electrical capacity the home actually requires.

Simply counting breakers isn't enough.

An electrical system can have empty breaker positions without necessarily having enough available capacity for a substantial new load.

Likewise, a panel that looks crowded doesn't automatically tell you the home's calculated electrical demand.

A qualified electrician evaluates the home's electrical loads using the applicable calculation methods and considers both existing equipment and proposed additions.

This becomes particularly important when adding major loads such as EV charging, electric HVAC equipment or other high-demand appliances.

Determine the Appropriate Service and Panel Size

After evaluating the electrical system and anticipated loads, the electrician can determine the appropriate equipment for the project.

Residential services may have ratings such as:

• 100 amps
• 125 amps
• 150 amps
• 200 amps
• Other configurations depending on the property

A 200 amp service is common in modern residential applications, but that doesn't mean every house automatically requires 200 amps.

The correct service size depends on the home's calculated electrical requirements and overall installation.

For a deeper explanation, read our guide to 100 Amp vs. 200 Amp Electrical Panels .

Plan for Future Electrical Needs

Replacing a panel can be an opportunity to think beyond today's electrical requirements.

Imagine upgrading a panel today and then purchasing an EV two years later, installing a heat pump after that, and adding another significant electrical load a few years down the road.

Planning for foreseeable needs can sometimes reduce the need to redo work later.

An electrician may discuss whether it makes sense to provide additional circuit space or capacity for anticipated projects.

Determine Permit and Utility Requirements

Electrical panel replacement and service upgrades may involve permits, inspections and utility coordination.

California is currently operating under the 2025 California Building Standards Code, effective January 1, 2026. Part 3 is the California Electrical Code, which incorporates the 2023 National Electrical Code with California amendments.

Local requirements also matter because the authority having jurisdiction administers permits and inspections applicable to a particular project.

If a project affects the electrical service connection, meter equipment or utility infrastructure, additional coordination may be required before work begins.

This is one reason homeowners shouldn't assume a service upgrade is simply an electrician arriving and changing the breaker box.

Coordinate the Electrical Service Disconnect

Replacing service equipment generally requires the electrical supply to be safely disconnected.

Exactly how that occurs depends on the existing equipment and project.

For projects involving utility service equipment, coordination may be required so the electrician can safely perform the work and service can subsequently be restored.

Homeowners should therefore expect at least some period without electrical power during many panel replacement projects.

Before the scheduled work, it can be useful to plan for:

• Refrigerators and freezers
• Internet equipment
• Medical or accessibility equipment requiring electricity
• Home offices
• Security systems
• Garage doors
• Electric cooking
• EV charging

Your electrician can explain the anticipated outage based on the specific project.

Remove the Existing Electrical Panel

Once the electrical system has been made safe to work on, the existing panel equipment can be removed as required by the project.

The electrician can then inspect conditions that may not have been visible before the old equipment was opened or removed.

This can sometimes reveal:

• Damaged conductors
• Corrosion
• Heat deterioration
• Improper previous modifications
• Grounding or bonding concerns
• Physical damage
• Other deficiencies

Discovering an existing problem doesn't necessarily mean the entire home needs to be rewired.

It does mean the electrician needs to determine what corrections are appropriate before the new equipment is placed into service.

Install the New Electrical Panel

The new panel or service equipment is then installed according to the approved project design, applicable requirements and equipment manufacturer's instructions.

Depending on the project, this can involve installing or configuring:

• The new panel enclosure
• Main disconnect equipment
• Circuit breakers
• Service conductors
• Grounding and bonding components
• Conduit or raceways
• Meter equipment
• Existing branch circuits
• New circuits included in the project

This portion of the project requires careful workmanship because the panel becomes the central distribution point for the home's electrical circuits.

Reconnect and Organize the Existing Circuits

Existing branch circuits that are being retained must be properly connected to the new equipment.

This is also an opportunity to improve panel organization and circuit identification.

A clear panel directory makes it much easier to determine which breaker controls a particular area or appliance.

Instead of mystery labels such as "Bedroom?" or "Old outlets", a properly identified panel helps homeowners and electricians understand the system more quickly.

Address Grounding and Bonding

Grounding and bonding are critical parts of the electrical system.

They help provide an effective fault-current path so protective equipment can operate when electrical faults occur.

Panel replacement or service-upgrade work may require evaluation of existing grounding and bonding arrangements and corrections appropriate to the new installation.

Complete Inspection and Testing

Before the project is considered complete, the installation needs to be checked and tested.

Where permits are required, the applicable inspection process must also be completed.

Depending on the project, the electrician may verify:

• Proper equipment installation
• Breaker configuration
• Circuit connections
• Grounding and bonding
• Equipment labeling
• Panel directory
• Operation of connected circuits
• Required clearances
• Other installation requirements

If utility service was disconnected or modified, service restoration may also need to be coordinated as part of the process.