A panel and an electrical service are different parts of the system
The panel distributes electricity to property circuits. The service is the incoming supply and associated equipment. Replacing a panel does not automatically increase the available supply. A Licensed Electrical Contractor should assess existing condition and demand, planned loads and the utility requirements before recommending equipment. Spare breaker spaces alone do not establish capacity.
Prepare the scope for your Mississauga property
List existing major loads and the upgrades you genuinely expect to make. Identify whether the existing panel needs replacement for condition, more circuit positions, additional capacity or a combination of these reasons.
Ask for the basis of the proposed size and the options considered. Avoid paying for a larger service merely because it sounds future-proof; the contractor should connect the recommendation to your actual load and project.
What should the assessment establish?
Treat the modernization list as a sequence of confirmed projects, not a reason to buy the largest service offered. For your Mississauga home, ask the contractor to show which present installation concern and which new load each part of the proposal addresses. If a later appliance choice is undecided, separate the cost of preparation from the cost of the work needed now. A phased proposal should explain whether later work would repeat an outage or disturb completed surfaces. That allows you to compare a coordinated change with several smaller projects on the same basis.
Questions before you agree to work
Does every new load need a larger service?
No universal service size applies to every project. The contractor must assess the existing system and proposed demand, and explain whether a service change, another design or no capacity change is appropriate.
Who arranges utility and ESA steps?
Confirm this in the written scope. Service work may need utility coordination as well as ESA notification and review. Ask the contractor what they arrange and what the owner must supply or authorize.