Rough estimate to upgrade to 400 amp service

[Brandon Brown]

I am considering switching to a heat pump with an electric heat strip for supplemental heating in our two-flat building, with plans to add a third unit in the future. Currently, we have a 200-amp service to the building, split into two 100-amp main panels for each unit. I'm concerned that the combined load of heat pumps and ancillary heat strips, along with other appliances, might exceed the 100-amp capacity during winter.

As part of our future plans to add a third unit and separate the utilities, we intend to install two additional meters: one for common areas and one for the new unit. I am looking for insights from anyone who has recently upgraded their electric service in Chicago. Specifically, I'm curious about the cost and process involved.

I'm considering upgrading to a 400-amp service, which I believe could be divided into two 125-amp panels, one 100-amp panel, and one 50-amp panel or some other combination. From what I've read, some electric providers might not charge for the new service upgrade itself, but adding the meters, connecting the upgraded service and adding/updating panels would require an electrician, which would incur costs.

If anyone has experience with this type of electrical service upgrade, particularly in Chicago, I would appreciate your advice and any information on costs and the process involved.