100 Amp vs 200 Amp vs 400 Amp Service: Which One Does Your Home Need?

What Does Electrical Service Size Mean?

Electrical service size refers to the maximum electrical capacity available to your home from the utility. It determines how much power your electrical system can safely deliver to lighting, appliances, heating and cooling equipment, EV chargers, and other electrical loads operating at the same time.

As modern homes continue to add high-demand equipment such as electric vehicle chargers, heat pumps, hot tubs, and basement suites, having adequate service capacity has become increasingly important. An undersized electrical service can limit future upgrades and may require a service or panel upgrade before additional circuits can be installed.

• 100 amp service is commonly found in older Ontario homes with moderate electrical demand.
• 200 amp service has become the standard for most new homes and major renovations.
• 400 amp service is typically installed in large custom homes or properties with multiple high-demand electrical systems.

Actual electrical capacity depends on your home's total electrical load. A licensed electrician should perform a load calculation before recommending a service upgrade or installing new high-demand equipment.

100 Amp Service

Many homes built before the 1990s were originally designed with 100 amp electrical service. While many of these systems continue to operate safely, today's electrical demands are considerably higher than when these homes were built.

Adding equipment such as EV chargers, heat pumps, hot tubs, or a finished basement can significantly increase the electrical load, making a professional load calculation essential before installing new circuits.

• Common in older Ontario homes
• Suitable for moderate electrical demand
• Can support many modern appliances
• May require a service upgrade before adding high-demand equipment

200 Amp Service

A 200 amp electrical service is the current standard for most newly built and extensively renovated homes in Ontario. It provides sufficient capacity for today's electrical needs while allowing room for future upgrades without immediately reaching the service limit.

For most homeowners, a 200 amp service comfortably supports both current electrical usage and planned additions for years to come.

Commonly supports:

• Level 2 EV chargers
• Heat pumps and electric HVAC systems
• Hot tubs and pools
• Basement apartments and home additions
• Modern kitchens with multiple large appliances
• Future electrical expansion

400 Amp Service

A 400 amp electrical service is generally reserved for large custom homes and properties with exceptionally high electrical demands.

While not necessary for most homeowners, 400 amp service can be beneficial when multiple major electrical systems operate simultaneously.

Large homes with significant electrical demands may require multiple panels and higher-capacity electrical service.

• Multiple EV chargers
• Large homes exceeding 4,000–5,000 sq ft
• Pools, spas, and extensive outdoor electrical systems
• Large workshops or home businesses
• Luxury homes with significant electrical loads

Signs You May Need a Service Upgrade

Homeowners often discover their electrical service is undersized when planning renovations or installing new equipment.

• Frequent breaker trips
• Limited panel space
• Installing an EV charger
• Adding a heat pump
• Major home renovation
• Building a basement apartment
• Installing multiple high-demand appliances

How Electricians Determine the Right Service Size

Choosing the appropriate electrical service involves more than simply installing the largest panel available. Licensed electricians perform load calculations based on the home's square footage, major appliances, heating systems, EV chargers, and future expansion plans.

This process helps ensure the electrical system is properly sized, code compliant, and cost effective.

Which Service Size Is Right for Your Home?

A 100 amp service may still be suitable for some smaller homes, but many homeowners upgrading their electrical systems choose 200 amp service to accommodate future needs. In larger custom homes with multiple high-demand systems, 400 amp service may provide the capacity required for long-term reliability and convenience.