I have a moderately sized electrical panel and over the course of the last 8 years have done a full house rewire, and installed heat pumps (and when I say 'I did X', I mean I wrote the check to the electrician). At the beginning the panel was relatively empty because the house was completely under-wired. Now, all the breaker slots are completely full, some with double breakers. Additionally, the system is set up with the mains wiring coming in through a 220v breaker instead of through the top bus bars, which seems weird to me. Breaker box photo

Within the last year I put in the Sense energy monitor, which involves putting two inductive clamps over the mains feed. I was able to do it, but it was a really tight fit to get it in place. https://sense.com/installation

I'm about to have a solar install done, and they'll have an electrician in anyway doing the hookup. They're willing to upgrade me to a larger box for the cost of 1 days work of an electrician and his apprentice, $1200.

The solar company seems to think they can get the solar installed in my existing box, with no problems. However, I think this might be a good opportunity to get a larger box so I don't have to worry about it in the future.

I have several opinion questions.

  1. Should I enlarge my box? In theory, I don't plan to add any more circuits to the house, but this sounds like a good opportunity to future proof. On the other hand, I don't want to throw $1200 at something if I don't have to.

  2. Should I insist on the mains being moved to what I believe is the more standard top-center point directly on the bus bars?

  3. Does $1200 and 1 day's work for 2 guys sound like a reasonable estimate for replacing the box in the Boston area? I'm not asking if someone could do it for $100 cheaper, but, just a basic call on whether this price seems reasonable?



Decided to pull the trigger and will be getting a contract amendment to the solar job to bundle the box upgrade. Thanks everyone.

  • Your cost estimate seems reasonable. I had to replace a much smaller panel at a cabin in California and it cost me $4700. But do get more than one estimate. You may be dealing with a low ball quote from inexperienced people.
    – Michael Karas
    Nov 8, 2019 at 15:19
  • Installing a second panel as a subpanel will probably be cheaper because there's not the time and labor to remove all the wires from the old panel and fish them into a new one. That is what takes all day. A subpanel could be installed in a few hours.
    – JPhi1618
    Nov 8, 2019 at 15:23
  • @MichaelKaras: I normally agree fully with you about multiple quotes. However, this is going through the tame electrician working for a big solar install company in the area as part of their solar install job, and bundling it with the install of all my solar inverter and grid interconnect tech.
    – A Holman
    Nov 8, 2019 at 15:26
  • @JPhi1618: Is there a downside to the sub-panel option? Given that its an unfinished basement, I don't care much about space or looks. I already have a sub-panel on the 3rd floor that was put in to feed additional circuits up there. Is there any limitation to the number of subs that I can have?
    – A Holman
    Nov 8, 2019 at 15:30
  • @JPhi1618: If I asked for a sub-panel instead, is the side breaker entry point for the mains weird, and should I ask them to change it, or just leave it alone and add a sub-panel for extra breakers?
    – A Holman
    Nov 8, 2019 at 15:31

2 Answers 2


Yes I think you should upgrade the panel now, but that is really just an opinion, partly based on disliking split breakers. Making changes after the solar install could get more complicated.

If you decide not to change the panel then no, you shouldn't move the service feeder wires to the directly to the main lugs. You need overcurrent protection for the panel. I do question if the existing stab in "Main Breaker" is Listed for use as Service Equipment, usually some type of screw or bracket is present to secure stab-in breakers to the panel https://www.gexpro.com/usg/Root-Category/Power-Distribution/Circuit-Breakers/Circuit-Breaker---Accessories/Hold-Down-Kits/GE-THQLRK1-Main-Breaker-Retainer%2C-PowerMark-Gold%2C-12-42-Circuit%2C-THQL/p/79046 , I just don't see it. Depending on panel model you may be able to get a kit to mount a main breaker to replace the main lugs.

$1200 sounds within reason, but that's not a two men for 8 hour price or job.

  • Thanks, for your input. I've decided to tell them to go ahead and put in a new box.
    – A Holman
    Nov 8, 2019 at 21:03

I would shift this panel to the left as far as possible without causing serious wire-reach problems (obviously a few wires e.g. the conduit will have to be temporarily removed).

Then, put a new panel just to the right of it, linked with conduit nipples. For this panel, I would use about a 30-space with a separate (not backfed) main breaker, either by buying an upgradeable main-lug panel, or a main-breaker panel and downswapping the main breaker.

This panel becomes a subpanel of the current main. But follow the bouncing ball: The purpose of the shift to the left is to position this panel to become the new main panel, with the old panel now as a subpanel.

For now, feed the new subpanel off the top main lugs of the old panel via #3 Cu wire (since it's such a short run). Since the old panel is backfed, the main lugs are under the 100A breaker's protection. If you get a "through-lug" type subpanel, you can just go to those.

When you convert the new panel to the new main, you can fit the main breaker (possibly with a service bump). If it's still 100A, you can keep using the through-lugs to feed the old panel. If you upsize service and the main breaker goes up, fit a 100A breaker in the new main, and feed the old panel from that. Look! There's one in the old panel that will no longer be relevant, and it's usable if the new panel is the same family (e.g. Homeline or Murray) as the old.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.