Electrical service and panel upgrade field guide

A service or panel upgrade, and what actually changes

A service or panel upgrade is the work of increasing a building's electrical capacity, replacing the load center, or both, so the system can carry more load or stop being a hazard. The word covers two jobs that get talked about as one. Raising the amperage of the whole service is one job. Swapping out the panel behind the meter is the other. They overlap, but they are not the same scope, and quoting one when the building needs the other is how a job goes sideways.

Three things drive the work. The building needs more load than the service can carry, usually a car charger, a heat pump, an addition, or the slow electrification of a house that used to burn gas. Or the panel itself is the problem: full, old, or one of the load centers with a documented failure history. Or a sale, an insurer, or an inspection forced the issue. Anvilfield's load-calculation guide is where the amperage number comes from, and the service-entrance and metering guide covers installing the service hardware itself. This guide is about deciding the scope, coordinating it, and not getting hurt doing it.

What makes this work different from a remodel circuit is where it lives. An upgrade reaches back to the utility's conductors, the meter, and the main, the parts of the system that have no breaker in front of them. That is the whole reason a service upgrade is not a weekend project and not a job you start by cutting anything.

What is the difference between a service upgrade and a panel replacement?

A service upgrade raises the amperage of the entire service: the utility feed, the meter equipment, the service entrance conductors, the main disconnect, and the grounding, all sized up to the new rating, commonly from 100 A to 200 A. A panel replacement swaps only the load center on the same service, keeping the existing amperage. The difference is whether the rating of the whole supply changes or just the box the breakers live in.

Get the distinction straight at the estimate, because the cost and the coordination split on it. A panel swap on an adequate 200 A service is a one-day job: kill the power, move the circuits to the new panel, reland, inspect, energize. A service upgrade pulls in the utility, a new meter base, often new service conductors, and a documented outage, because you are changing the rating of conductors the utility owns or feeds.

The trap is selling a panel swap when the building needs more amperage. A customer asks for a bigger panel so they can add a car charger, and a bigger box with more breaker spaces does not give them one more amp of capacity if the service behind it is still 100 A. More spaces is not more service. The load calculation tells you which job you are actually doing, and it is the first thing to run, not the last.

When do you need a service or panel upgrade?

You need an upgrade when one of a short list of triggers shows up, and most jobs are one of them. Added load is the common one: a Level 2 car charger, a heat pump or a mini-split system, a heat-pump water heater, an induction range, a shop, or an addition. Each of those is real continuous load, and a 100 A service that was sized for a gas house in 1985 runs out of room fast when the gas appliances start coming out.

The panel itself is the next trigger. A full panel with no open spaces and tandem breakers already doubled up has no room for a new circuit. An old 60 A or 100 A service is undersized for a modern all-electric house regardless of the panel. And a panel from one of the lines with a known failure history is a safety-driven replacement on its own, load or no load.

Then there is the paperwork trigger. A home inspector flags the panel at sale, an insurer refuses to write or renew a policy over a recalled load center, or a jurisdiction requires the service to be brought current as a condition of other permitted work. These get the upgrade moving whether or not the owner wanted to spend the money. The honest call is to run the load calc and look in the panel before promising anyone what the job is, because the trigger and the right fix do not always match.

The load calculation sizes it, not a round number

The service size comes from the NEC load calculation, not from a habit of installing 200 A on everything. Article 220 totals the connected load, applies the demand factors, and returns the minimum service in amps. That number tells you whether the building needs 100, 150, 200, or 400 A, and whether the existing service has the room for the new load or has to grow. Anvilfield's load-calculation guide walks the procedure; do that work before you quote a service size.

On an existing building there is a better tool than recalculating from nameplates. The NEC permits sizing off the measured maximum demand, commonly cited at 220.87, using a year of utility data or a 30-day recording on the highest-loaded phase, taken at 125 percent. Subtract that from the service rating and you have the real spare capacity. The paper recalculation is almost always more conservative than the building's actual draw, and on a retrofit that conservatism is what pushes people into a service upgrade they may not need.

Guessing the size is the expensive mistake at both ends. Undersize it and the new load trips the main or forces a second upgrade in two years. Oversize it and the customer pays for copper and gear that will never carry the current. Worse, an upgrade quoted without a calc has no defensible basis when the inspector or the next electrician asks why the service is the size it is. Run the number, size to it with named headroom for the load you can actually point to, and keep the calc with the job.

The recalled and unsafe panels: Federal Pacific, Zinsco, Challenger

Some panels are a replacement on their own merits, with no added load involved, because the breakers do not reliably do the one thing a breaker exists to do: trip on an overload or a fault. Federal Pacific Electric Stab-Lok panels are the worst-known case. Independent testing has shown high failure-to-trip rates on FPE breakers, and there is a long-documented history including questions about the original UL testing. A breaker that does not trip lets an overload keep heating the wire, which is how a panel starts a fire instead of preventing one.

Zinsco and the related Sylvania-Zinsco panels fail a different way. The breakers can melt or weld to the bus, so a handle that reads off is still feeding the circuit, and the bus itself degrades. Challenger panels, common in homes built roughly 1970 to 1990, have a history of overheating breakers and bus connections. Across all three the through-line is the same: the protection you are counting on may not be there when the fault comes.

Treat these as safety-driven replacements and say so plainly. You cannot fix a Stab-Lok panel with new breakers, because the problem is the panel and the stab connection, not just the breaker, and replacement breakers for these lines are a gray market you should not trust a life to. Insurers know this, which is why many will not write a policy over one. The same logic applies to a fuse panel in a building that has outgrown it: fuses protect fine when they are the right size, but they get bypassed with oversized fuses or pennies, and an old fuse service is usually undersized for a modern load anyway. When the panel is the hazard, the upgrade is not optional maintenance. It is the point of the job.

Utility coordination and the disconnect you cannot make yourself

The utility has to be in the loop on a service upgrade, and on most of them the utility is the one who actually kills the power. The conductors feeding the meter are the utility's, energized, and have no customer-side overcurrent device in front of them. You do not cut them, pull them, or work them hot. You call the utility, they de-energize at the transformer or pull the connection, and only then does the service become something you can touch. This is the part of the job that drives the schedule and the part that gets people killed when it is skipped.

Coordinate early, because the utility's lead time usually beats the wiring time. The utility publishes a service requirements document or service handbook that controls the meter equipment they will accept, the meter location and height, who furnishes and installs the drop or lateral, and the clearances. They also schedule the disconnect and reconnect, and on a meter pull they set and seal the new meter. Apply for the upgrade, confirm the new meter base is on their approved list before you order it, and get a disconnect window scheduled before you tell the customer a date.

There are jobs where you can pull and reset your own meter under a utility seal program, and jobs where only the utility may break the seal. Breaking a utility seal without authorization is a problem that follows you. Know which program the serving utility runs before you put a hand on the meter. The rule that never changes is the one on the line side: the conductors ahead of the main are not yours to interrupt, and the utility is the authority that makes them safe to work.

Do you need a permit to upgrade an electrical panel?

A service or panel upgrade needs a permit and an inspection in essentially every jurisdiction, and the inspection is what releases the utility to reconnect. The authority having jurisdiction, the AHJ, issues the permit and inspects the work to the adopted code. On a service upgrade the inspection result, commonly called the green tag, is the gate: no green tag, no meter, no power. Pulling a meter and swapping a service without a permit is the kind of unpermitted work that surfaces at the next sale and gets torn back open.

What the inspector checks on an upgrade is predictable, so build to it. The disconnect location and the working clearance in front of the gear come first, before the wiring. Then the grounding electrode system and the bonding, the main bonding jumper at the service and the neutral-ground separation downstream, the conductor and breaker sizing against the load calc, the labeling, and any current-code items the upgrade triggers such as the outdoor emergency disconnect and surge protection. The exact list and the adopted edition vary, so confirm with the AHJ what the upgrade pulls in.

The sequence is the thing crews get wrong on scheduling. The AHJ inspects, the green tag issues, and the utility energizes, in that order, and the utility will not jump the line. Stack those lead times in the schedule instead of discovering them on cutover day with the customer's power off.

The service components an upgrade touches

An upgrade reaches across the whole service, and naming the parts keeps the scope honest. From the utility in, the chain is the service drop or lateral, the meter and its base, the service entrance conductors, the main disconnect, the panel, and the grounding electrode system. A panel swap touches the last two or three. A full service upgrade touches all of them, because raising the amperage means everything in the path has to carry and survive the new rating.

Which parts you actually replace depends on what is already there and what the new rating demands. The meter base often has to grow, because a 100 A socket is not rated for a 200 A service. The service conductors often have to grow, because the old ones were sized to the old load. The main and the panel are new by definition. The grounding gets brought current, which on an old service usually means more than it had. The drop or lateral may be the utility's to upsize, which is one more reason to have them in the conversation early.

Anvilfield's service-entrance and metering guide covers installing these components in detail, including overhead versus underground, self-contained versus CT metering, the disconnect location rule, and available fault current. The upgrade-specific point is that you are rarely starting from a blank wall. You are replacing a live, in-service system in a limited outage, which means the order of operations and the utility's window matter as much as the hardware.

Sizing the service conductors for the new amperage

When the service amperage goes up, the service entrance conductors usually go up with it, sized to the new rating and confirmed against the conductor tables and the terminal temperature column. A 100 A service running, say, #4 copper or #2 aluminum does not have the conductors for a 200 A main. The NEC also recognizes a dwelling service sizing allowance that lets the main service conductors for a typical 120/240 V single-phase dwelling run a step smaller than a general feeder of the same rating, but confirm the size against the adopted edition rather than from memory, because that allowance has its own table and conditions.

The conductors ahead of the main are a different animal from a feeder because they have no overcurrent protection in front of them inside the building. They are sized to the load and the main rating, and the available fault current, not the load, often drives the gear selection. On any service upgrade get the available fault current from the utility in writing, because a shorter, fatter conductor run on the new service can actually raise the fault current at the gear, and the new panel's rating has to exceed it.

Anvilfield's service-entrance guide carries the conductor and ampacity detail. The upgrade reminder is to check terminations as hard as conductors. Lugs are rated for a conductor range and a temperature column, and pushing a 200 A conductor into a lug that does not accept it makes a hot connection at the exact spot where heat already concentrates.

The main breaker, the busbar, and the new panel

The new panel is selected off the calculated load, the busbar rating, and the number of circuits the building needs now and is likely to need soon. The main breaker sets the service rating: a 200 A main makes a 200 A service, provided the conductors, meter, and busbar all carry it. NEC Article 408 governs the panelboard, and the rule that matters most is that the panelboard has to be protected by an overcurrent device rated no greater than the panel, and its short-circuit current rating has to meet or exceed the available fault current. A panel with a busbar rated below its main is a panel waiting to fail at the bus.

Buy the busbar rating, not the breaker count. Two panels can both say 200 A and have very different busbar construction, and the cheap one is the one that runs warm at the bus under a real continuous load. Look at the number of branch spaces too. The old 42-circuit cap on a single panelboard is gone in recent editions, with the limit now set by the manufacturer's listing, so a modern single-main panel can carry more circuits than the old rule allowed, but the physical spaces still run out. Size the spaces for the circuits plus honest room for the EV, the heat pump, and the future, because filling a brand-new panel to the last space the day it goes in is its own callback.

Choose between a main-breaker panel and a combination meter-main based on where the disconnect needs to live and what the utility and the emergency-disconnect rule require. A combination meter-main puts the service disconnect right at the meter outdoors, which is often the cleanest way to satisfy the outdoor disconnect requirement and keep the unprotected conductor run short.

Bringing grounding and bonding up to current code

An upgrade is the moment to bring the grounding electrode system and the bonding current, and on an old service that usually means adding to what was there. The grounding electrode system ties the service to earth through the grounding electrode conductor and the electrodes present at the building: a concrete-encased electrode the trade calls a Ufer, ground rods, metal underground water pipe, and building steel. The NEC requires every qualifying electrode present to be bonded into one system. Old services were often grounded to a single rod or a water pipe and nothing else, and the upgrade is where that gets corrected.

The bonding is the part rookies treat as an afterthought and inspectors check first. The main bonding jumper ties the neutral to ground at the service, once, at the main disconnect. Downstream of that disconnect the neutral and the equipment grounding conductor stay separate. When you replace a panel, this is the rule that bites: a panel that used to be the main becomes a subpanel after an upgrade adds a new main ahead of it, and the bonding strap that belonged in the old main has to come out of the now-downstream panel. Leave it in and you put neutral current on the conduit and the equipment grounds, where it makes stray voltage and defeats the protection.

Anvilfield covers electrode selection, the rod resistance rule, and grounding-electrode-conductor sizing by topic. The upgrade-specific habit is simple: bring every electrode present into one system, land the GEC at the new service, and confirm there is exactly one neutral-to-ground bond in the whole building. The rod in the dirt is not the fault-clearing path. The breaker trips on the bonding back to the source, and the upgrade is your chance to make sure that path is whole.

The meter, the base, and the combination meter-main

The meter base, the socket the utility's meter plugs into, usually has to be replaced on a service upgrade because the old socket is not rated for the new amperage. A 100 A meter socket cannot carry a 200 A service, and the socket is equipment you furnish and install from the utility's approved list, while the meter itself stays the utility's to set and seal. Mount it plumb, at the height the utility's handbook specifies, land the line and load conductors on the right lugs, and leave the meter for them.

A combination meter-main combines the meter socket and the service disconnect in one outdoor enclosure. On an upgrade it earns its place two ways: it keeps the unprotected service conductors from running deep into the building before they hit a disconnect, and it often satisfies the outdoor emergency-disconnect requirement in the same box. The trade-off is that the main now lives outside in the weather, so the gear has to be rated for the location and the customer reaches for the disconnect outdoors.

On larger upgrades the metering crosses from self-contained, where the full current runs through the meter, to current-transformer metering, where CTs step the current down to a signal the meter reads. The crossover varies by utility, commonly landing near 400 A single-phase or above 200 A three-phase. Anvilfield's service-entrance guide covers the metering types in full. The upgrade decision is to confirm the metering type off the new service size and the utility's table before the socket or CT cabinet is on the order, because getting it wrong means the whole front end is wrong.

Subpanels and feeders off the upgrade

Adding capacity often means adding a subpanel, not just a bigger main panel, especially when the new load lives away from the service: a detached garage, a shop, an addition, or a car charger at the far end of the property. The subpanel is fed by a feeder sized to its own load calculation and protected by an overcurrent device at the main panel. The feeder, not the branch wiring, is what carries the load out to the remote panel, and on a long run it gets the voltage-drop check on top of the ampacity check.

The detail that separates a clean subpanel from a hazard is the four-wire feeder and the bonding. A subpanel feeder carries two ungrounded conductors, a neutral, and a separate equipment grounding conductor, four wires, because the neutral and the ground must stay separate at the subpanel. The neutral floats on its own insulated bus, the equipment grounding conductor lands on the bonded ground bus, and the bonding strap stays out. The old three-wire feeder to a subpanel, where the neutral did double duty as the ground, is not how a new subpanel gets wired.

Anvilfield covers feeder sizing and subpanel bonding by topic. On the upgrade the point is to plan the subpanels into the load calc and the panel schedule up front, so the new main has the spaces and the capacity for the feeders, and so the long run to the charger is sized for the distance before the conductor is on the truck.

Does a panel upgrade trigger AFCI and GFCI requirements?

An upgrade can pull in current-code arc-fault and ground-fault requirements, but the line between what is required and what is grandfathered is narrower than people assume, and it is an AHJ call. The clean rule is that new circuits and the protected areas they serve get current-code AFCI and GFCI protection. A new kitchen circuit, a new bathroom receptacle, a new bedroom circuit added during the work gets the protection the adopted code now requires.

The reconnected existing circuits are the gray area. The NEC has carried an allowance, commonly cited at 210.12, that reconnecting existing branch circuits to a replacement panel does not by itself require adding AFCI protection to those circuits, with limits on how far you can extend a circuit before the protection kicks in. So a straight panel swap that relands the same circuits is not automatically a whole-house AFCI retrofit under the NEC. But some jurisdictions amend toward requiring it on a panel change, and some inspectors expect it, so this is exactly the kind of point to confirm with the AHJ before you quote it, rather than assume either way.

The practical move is to ask the AHJ what a panel change triggers in their jurisdiction and price it in, because the difference between reusing standard breakers and populating a panel with combination AFCI and dual-function breakers is real money on the quote. Anvilfield covers GFCI and AFCI requirements by topic. The hedge that keeps you honest is that the adopted edition and local amendments control which circuits need which protection on an upgrade.

The outdoor emergency disconnect requirement

Recent code editions added an outdoor emergency disconnect requirement for one- and two-family dwellings, and a service upgrade is one of the events that pulls it in. The requirement, commonly cited at NEC 230.85, calls for a disconnecting means in a readily accessible outdoor location on or within sight of the dwelling, so a first responder has an exterior way to kill the house in a fire or a flood. It can be the service disconnect itself, a disconnect built into the metering equipment, or a listed disconnect ahead of the service, and where there is more than one it has to be marked.

The trigger is the scope of the work, and this is where the service-versus-panel distinction earns its keep. The requirement generally applies where the service equipment is replaced, which a service upgrade and most panel changes are. Where only the meter socket, the service entrance conductors, or related raceways are replaced, it generally does not apply. The 2023 edition tightened the rating language, requiring the disconnect to be marked and rated, and later editions have continued to refine it. The exact text, and which editions a jurisdiction has adopted, vary, so confirm the requirement and the marking against the adopted edition and the AHJ.

On a real upgrade the cleanest way to satisfy it is often a combination meter-main outdoors, which puts the disconnect at the meter and keeps the unprotected conductors short at the same time. Whatever form it takes, it is not retroactive to existing homes that are not having qualifying work done, so the trigger is the upgrade, not the calendar.

The work, the outage, and the sequence

A service upgrade is a planned outage, and the sequence is what keeps the outage short and the work safe. Roughly: the permit is pulled and the utility disconnect is scheduled, the new gear and grounding are staged, the utility de-energizes, the old service comes out and the new meter base, main, panel, and grounding go in, the circuits are relanded, the AHJ inspects, the green tag issues, and the utility reconnects and sets the meter. The customer is without power from the utility disconnect to the reconnect, and that window is the thing they care about most.

Plan the outage like the customer is in the room, because they are. A straightforward residential 100 A to 200 A upgrade is often a one-day outage when the utility cooperates on timing, but the reconnect waits on the inspection, and the inspection waits on the AHJ's schedule. If the inspection cannot happen the same day, the customer is dark overnight unless you arrange a temporary feed or stage the work around it. Tell them the realistic window, including the part you do not control, before cutover day.

Stage everything reachable before the power goes off. The grounding electrode work, the rod or Ufer connection, the new panel mounting, the conduit, the circuit identification, all of it that can be done live or done cold without the utility, gets done before the disconnect so the dead time is spent on the work that actually needs the power off. The crews that run long outages are the ones who start staging at the disconnect instead of before it.

The line side has no breaker in front of it

The service conductors ahead of the main are line side, which means there is no overcurrent device between them and the utility transformer. On a fault, the only thing that clears them is the utility's protection far upstream, and until then they deliver everything the transformer can push. That is a different hazard class from anything downstream of a breaker, and it is why a service upgrade is qualified work, not a homeowner job and not an apprentice working alone.

Verify dead, every time, no exceptions. After the utility disconnects, you confirm the service is de-energized with a meter you just proved on a known live source, test-before-touch, before you put a hand on a conductor. An open visible disconnect is not proof by itself. A pulled meter is not proof by itself. The meter on the conductor is the proof. NFPA 70E governs the electrical safety side of this work: the shock approach boundaries, the arc-flash hazard, and the personal protective equipment for the energy available at the service, which on a service entrance is real arc-flash energy, not a nuisance.

Do not work the line side hot to save a trip charge or a schedule day. The conductors feeding the meter are the utility's and they are energized until the utility makes them dead. The fastest way to turn a routine upgrade into a fatality is to cut, strip, or land a line-side conductor that someone assumed was off. Coordinate the disconnect, prove it dead, and treat the line side as live until the meter says otherwise.

Can a smart panel or load management avoid a service upgrade?

Often, yes. Electrification is what is driving most residential upgrades now: a car charger, a heat pump replacing a gas furnace, a heat-pump water heater, an induction range, each adding continuous load to services that were sized for a gas house. The instinct is to upsize the service to fit them all running at once. But the building never runs them all flat out at the same instant, and that is exactly the gap a load-management system fills.

The NEC recognizes energy management systems that limit current by shedding load when the building approaches a setpoint, with the concept appearing around 220.70 and the broader energy-management rules, and the EV-specific version permitted under Article 625, commonly at 625.42, which lets an EV energy management system throttle or pause the charger when the rest of the house is drawing hard. A smart panel or a standalone load controller measures the whole-house load and holds the total under the service rating, so a 100 A or 125 A service can take a car charger it could not take wide open. This is code-recognized load management, not a load-splitting trick, and it can save a customer the cost of a service upgrade they do not actually need.

It is not the answer to every job. A building that is genuinely out of capacity, or one that needs the panel replaced anyway for age or a recalled load center, is a real upgrade. The honest version is to run the metered load study first, see how much room the service actually has, and then decide between managing the peak and raising the service. A device that sheds the charger is cheaper than new copper to the pole. A service that is already maxed and unsafe needs the copper.

Residential, commercial, and data-center service upgrades

The residential upgrade is the common job: a 120/240 V single-phase service, usually 100 A to 200 A, one meter, one main, one panel, and a utility that handles these every day. The 400 A class dwelling service, served by a 320 A continuous meter, shows up on large all-electric homes and homes with several chargers and a heat pump, and it changes the metering and the gear but not the basic logic.

Commercial upgrades scale up and bring in three-phase, 120/208 V or 277/480 V, larger gear, current-transformer metering, and available fault current that drives the gear ratings harder than the load does. The disconnect rules, the working clearance, and the labeling all carry more weight, and the coordination with the utility and the AHJ is a longer process. The single-versus-grouped disconnect rules and the larger conductor and bus ratings are where a commercial upgrade differs from a house, but the spine is the same Article 230 and Article 250 work applied to bigger iron.

At the top end, a data hall or a campus does not diversify the way an office does, because the racks run flat out around the clock, so the connected load and the design load converge and the service is sized close to the real continuous draw. An upgrade there is rarely one service: it is paralleling gear, redundancy tiers, and metering that all scale with the load, often coordinated with the utility as a capacity project rather than a service change. Anvilfield's service-entrance guide carries the large-service and medium-voltage detail. The point that holds across all of it is that the rules underneath do not change with the size. The load calc sizes it, the utility supplies it, the grounding bonds once, the gear meets the fault current, and the AHJ and utility both sign off.

What to document

An upgrade that nobody documented is one the next electrician has to reverse-engineer with the cover off and the service live. The record is what closes the permit, releases the utility, and answers the question two years out when someone asks why the service is the size it is or whether the grounding was ever brought current. Capture it as the work is built, not from memory after the meter is sealed.

Record the scope honestly, service upgrade or panel swap or both, and tie each piece to what it involved. The table below is the minimum a defensible upgrade carries, and it doubles as the scope sheet for the quote and the closeout.

Common mistakes

• Quoting a service size without running the load calc, then under or oversizing the whole upgrade.
• Selling a bigger panel for more capacity when the service behind it is unchanged, so the amperage never grows.
• Leaving an unsafe or recalled panel in service, or trying to fix a Stab-Lok panel with replacement breakers.
• Working the line side, or cutting the meter, without the utility de-energizing and without verifying dead.
• Doing the upgrade with no permit, so it has no inspection and no green tag and surfaces at the next sale.
• Not updating the grounding electrode system and bonding to current code while the service is open.
• Leaving the bonding strap in a panel that became a subpanel after a new main was added ahead of it.
• Ignoring the outdoor emergency disconnect, surge, and AFCI/GFCI items the upgrade triggers for the adopted edition.
• Sizing the panel SCCR below the utility's available fault current, which a shorter new service run can raise.
• Promising the customer an outage window without the utility disconnect and the AHJ inspection both scheduled.

Field checklist

Standards and references

The NEC, NFPA 70, is the framework. Article 230 covers the service from the utility connection through the service disconnecting means: the conductors, the disconnect location and number, the metering, and the outdoor emergency disconnect for dwellings at 230.85. Article 220 covers the load calculation that sizes the upgrade, including the metered existing-demand method at 220.87, reorganized into a new Article 120 in the 2026 edition. Article 250 covers grounding and bonding, the grounding electrode system, the main bonding jumper, and the neutral-ground separation downstream. Article 408 covers the panelboard, including the rule that the panel be protected at no more than its rating and have an SCCR that meets the available fault current.

The points to verify against the adopted edition, because they have changed and they vary by jurisdiction, include the outdoor emergency disconnect at 230.85, the AFCI treatment of reconnected circuits at 210.12, the energy-management and EV load-control rules around 220.70, 625.42, and Article 750, where surge protection is required, and the dwelling service conductor sizing allowance. The exact section numbers and the thresholds shift between code cycles, so confirm them against the edition the jurisdiction has actually adopted and any local amendments before citing them on a submittal.

Two authorities sit alongside the NEC on an upgrade, and both have to be satisfied. The serving utility's service requirements document controls the connection, the meter equipment, the location, and the disconnect coordination, and the utility is the one who de-energizes the line side. The AHJ issues the permit and the green tag that releases the utility to reconnect. NFPA 70E governs the electrical safety of the work itself. Where equipment is listed, the UL listing and the manufacturer's instructions govern the terminations and the ratings. Cite the authority that controls the point, treat the line side as the utility's until proven dead, and keep the work to qualified persons.

Units, terms, and the names on the job

An upgrade carries terms that read differently across a utility handbook, a permit, and the panel schedule, so the same part shows up under more than one name. Keeping them straight keeps the coordination clean.

Service size is in amps; the common residential jump is 100 A to 200 A, with a 400 A class dwelling service metered through a 320 A continuous socket. The load center is the panel or panelboard; the busbar is the bus. The main is the service disconnecting means. The meter base is the meter socket. A combination meter-main is one enclosure with both. The grounding electrode conductor is the GEC; the main bonding jumper is the single neutral-to-ground bond at the service. Available fault current is also called available short-circuit current; AIC is the device interrupting rating and SCCR is the assembly short-circuit current rating. An EVEMS is an EV energy management system, the load controller that throttles a charger to hold the service under its rating.

Service upgrade

Raising the amperage of the whole service: utility feed, meter, main, conductors, and grounding

Panel replacement

Swapping the load center on the same service, keeping the existing amperage

Combination meter-main

One outdoor enclosure with the meter socket and the service disconnect together

Main bonding jumper

The single connection of neutral to equipment ground, at the service only

Available fault current

The maximum fault current the utility can deliver, which the gear AIC and SCCR must exceed

EVEMS

EV energy management system that limits charger draw to hold the service under its rating

Green tag

The AHJ inspection approval that releases the utility to reconnect and set the meter

Related tools

Calculators and readiness checks for this work

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