Service size
400 amp electrical service
What 400A service means, what it may support and when capacity needs professional verification.
Short answer
A 400A service is used for unusually large or electrically intensive homes. It requires specialist planning and is not a default residential recommendation. The service number is a starting fact—not a substitute for calculated demand and equipment review.
Key takeaways
01400A does not describe the condition of every electrical component.
02Available breaker spaces and available service capacity are different.
03Plan several years of electrification before choosing an upgrade target.
What 400A means
The main service is designed around a 400-ampere rating when the full service equipment supports that rating. A visible label should still be verified in context.
When to verify
multi-panel distribution, utility capacity and engineered or detailed service design may apply. A qualified contractor should review actual demand, equipment nameplates and the applicable code method.
Upgrade choices
Possible outcomes include retaining the service, changing distribution equipment, using approved load management where suitable, or increasing service capacity.
Decision table
What the evidence changes
- Reported service
- 400A
- Capacity conclusion
- Requires load and equipment assessment
- Common misconception
- A larger panel label alone does not increase service
Typical project sequence
From question to documented work
- 01Confirm the service
- 02Inventory existing demand
- 03Add planned projects
- 04Compare retain / manage / upgrade
Sequence and responsibilities vary by jurisdiction, utility and scope.
Evidence
Sources and verification
Published by the 200AmpPanel.ca Research Team, a HAUSE specialist property. Updated 2026-08-31.
Questions
Frequently asked
Does 400A automatically need upgrading?
No. The answer depends on the home, current loads, planned equipment and local requirements.
What should I do next?
Use the Capacity Check to organize what you know, then have a qualified electrical contractor complete the assessment required for the property and jurisdiction.
Your next step
Bring the right facts to the first conversation.
Record the visible service clue, planned equipment and any relevant documents. The free brief organizes your questions; a qualified person verifies capacity and scope.