· by Michael Blair, Nashville's Electrician
Panel upgrades get recommended on sight of an older label and skipped in houses that genuinely need one. The two questions worth answering are whether the service is actually undersized for the load, and whether the panel itself is a known hazard. Those are the two things we look at on a panel upgrade visit, before anyone prices a new box.
Is a 100 amp service enough for a Nashville house?
In our experience a 100 amp service carries a great many Nashville houses without trouble, particularly ones with gas heat, gas water heating and a modest cooling load. Where we see it run short is electric heat, a heat pump with backup strips, a large shop, or an EV charger. The utility frames it the same way: NES’s Electric Service Guidelines say the size of a service depends on the size of the building and the power requirements of the equipment in it, and they leave working out those requirements to the customer.
A load calculation answers it properly. The electrician adds up what the house’s equipment draws and sets it against what the service can supply, instead of reading the number stamped on the main breaker, and it is the thing to ask for before agreeing to an upgrade. The Department of Energy’s page on charging at home says the same about chargers: an electrician can tell a homeowner whether the house has the capacity, and some homes do not have enough for Level 2 equipment. Our post on installing an EV charger in a Nashville home walks through that case.
When the panel itself is the problem
Some older panels deserve an electrician’s evaluation whatever their capacity, and Federal Pacific and Zinsco equipment is at the top of that list for us. When we find one, we open it up and look at the breakers and the bus before the conversation turns to amps, and we tell you plainly whether we would keep it in your house.
Beyond the brand, these are what we look for with the cover off: rust inside the enclosure, scorching or discoloration at any breaker, a burning smell, two wires under a terminal made for one, and a panel with no open spaces and no room for tandem breakers. A breaker that will not stay set is its own subject, and our post on a breaker that keeps tripping sorts out what it may be telling you.
- Federal Pacific or Zinsco equipment, worth an evaluation on sight
- Rust, scorching or a burnt smell in the enclosure
- Breakers that will not stay set
- Two wires under a terminal made for one
- No open spaces and no room for tandem breakers
What does a panel upgrade involve?
More than swapping the box. A service upgrade typically involves new service entrance conductors and often a new meter base, we check the grounding while the service is apart, and the utility has to be in on it. Under NES’s Electric Service Guidelines, an electrical release is required for a new service, for replacing conductor (including conductor the customer owns), and for adding load by changing the panel size, and the customer or electrician has to notify NES Customer Relations before the work begins. Replacing breakers, or a meter base with one of the same amperage when no wire is replaced, needs no release. The meter base on the side of your house is yours, installed and owned by the customer. With the service open, we also look at adding a protector at the panel, the one layer that reaches hardwired appliances like the furnace and the range, and our post on whole-house surge protection covers what it handles and what it cannot.
It is permitted work with an inspection, and the inspection is the point: this is the connection between your house and the grid. Metro Codes’ page on emergency electrical reconnects draws the line where NES’s service drop meets the house; from there through the meter base to the breaker panel, repairs fall to a licensed electrical contractor at the owner’s expense, and power comes back after the Metro electrical inspector releases the job to NES. The permit itself is pulled by the contractor, since Metro’s trades permit page accepts online applications only from licensed contractors with an e-permit account. Outside Davidson County, the State Fire Marshal’s Office issues electrical permits and inspects through most of Tennessee under the 2017 National Electrical Code, apart from the jurisdictions exempt from its program.
Adding a subpanel instead
Where the service capacity is adequate but the panel is simply full, a subpanel can be the smaller job and an entirely legitimate answer. It adds spaces without touching the service.
It only works if the load calculation supports it. Hang a subpanel off a service that is already at its limit and you gain places to put circuits while the service has nothing more to feed them, so the problem moves to a new box and stays unsolved. If you are weighing a subpanel against an upgrade, ask us for an estimate and we will do the load calculation before recommending either.
Sources
- Nashville Electric Service, Electric Service Guidelines (Version 21) — Service size depends on the building and its equipment; electrical release required for a new service, replaced conductor or a panel-size change, not for breakers or a same-amperage meter base; notify NES Customer Relations first; customer-owned meter base; planned outages on weekdays during business hours.
- US Department of Energy, Alternative Fuels Data Center, Charging at Home — Electricians judge whether a home has capacity for charging; some homes lack capacity for Level 2; EV charging is a continuous load under the NEC.
- Metro Nashville Codes, Emergency Electrical Reconnects — Owner responsibility from the NES service drop through the meter base to the panel; licensed contractor repairs; Metro electrical inspection and release to NES before power is restored.
- Tennessee State Fire Marshal’s Office, Electrical Permits — State electrical permits and inspections through most of Tennessee under the 2017 NEC, with exempt jurisdictions.
- Metro Nashville Codes, Trades Permits — Only licensed contractors with an e-permit account can apply for a trade permit online.
FAQ
When an Electrical Panel Actually Needs Upgrading — questions
Do I need 200 amp service for an EV charger?
Not necessarily. Whether a 100 amp service can carry a Level 2 charger depends on everything else the house runs, and a load calculation by an electrician is what settles it. The Department of Energy notes that some homes lack the capacity for Level 2 charging and that the National Electrical Code treats EV charging as a continuous load, so the charger goes into the calculation as one. Get the calculation before assuming an upgrade.
Does a panel upgrade need a permit in Nashville?
A service upgrade or a change in panel size does. In Davidson County that work goes through a Metro Codes electrical permit, pulled by a licensed contractor, and an inspection, and NES needs the Codes release before it reconnects the service. A like-for-like panel swap with no service change is worth confirming with Metro Codes before the work is scheduled.
How long does a panel replacement take?
It depends mostly on whether the service changes. The power is off while the panel is replaced, and a service upgrade adds the Codes inspection and the NES release before the house is reconnected. NES works planned outages during normal business hours, Monday through Friday, so we schedule the job for a weekday and tell you before we start how long the power will be off.
What is an electrical panel upgrade?
Replacing the panel, and often the service feeding it, so the house can supply more load. A service upgrade typically brings new service entrance conductors and often a new meter base, with the grounding checked while it is apart. NES requires an electrical release for it, and a Metro inspection comes before the power is reconnected.