The job
Modelled, not recorded. Every figure on this page is re-run through the calculator it names whenever the site is built; the estimate is worked, but no job was carried out, so the last section gives the mechanism of each likely error rather than a measured overrun.
A charger circuit is short on materials and long on decisions. The job here is a 48 A Level 2 unit, hardwired, fed from the house's existing 200 A panel along a 45 ft (13.72 m) route in 3/4 in EMT into an attached garage. The finished parts list is one two-pole breaker, three conductors, five sticks of EMT and the fittings that join them, and nearly every line on it is fixed by a number settled somewhere else first — which is why the takeoff below starts at the charger's rating and the service and ends at the conduit, rather than starting with the wire.
THE FIRST QUESTION IS WHETHER THE HOUSE CAN CARRY IT AT ALL. A charger draws its full current for hours at a stretch, so the code counts it at 125% — on this unit, 60 A of calculated load added to a service rated 200 A. That is settled by the whole-dwelling load calculation before any breaker is chosen, because free spaces on the bus say nothing about capacity on the service, and only capacity lets the job go ahead as drawn.
THE SECOND IS THAT THE WIRE SIZE DEPENDS ON THE LABELS AS WELL AS THE AMPS. The 60 A breaker fixes the minimum ampacity, but which column of Table 310.16 the conductor may be read in is set by the temperature rating marked on the breaker and on the charger's terminals. The site's wire-gauge calculator reads the conservative 60 °C column and returns 4 AWG (21.2 mm²); with 75 °C terminations at both ends, single THHN conductors in conduit are allowed at 6 AWG (13.3 mm²). Reading two labels before ordering is worth a whole conductor size.
WHAT THIS PAGE IS, AND WHAT IT LEAVES OUT. It is a US page, worked to the NEC's continuous-load and demand rules as the linked calculators apply them. Each result comes out of the calculator named at its step, or out of the code table that calculator quotes; the measured inputs and the few lines of hand arithmetic between steps are shown where they are used, with metric alongside, and nothing was installed. Three things the job needs are named here and not computed: the conduit fill, because the site's fill calculator cannot check this mix of conductor sizes; the ground-fault protection and any disconnect the charger's manual or the inspector calls for, which no calculator here checks; and the permit, which comes before any of it.
What was measured, and how
Charger rating as it will be configured, and how it connects
48 A continuous at 240 V (11,520 VA), hardwired; two lines and a ground, no neutral
Read off the unit's nameplate and installation manual, then confirmed at the output setting the installer will leave it on, since many units are adjustable. The continuous rating is the load. Entering the 60 A circuit size printed on the box as the load counts the continuous-duty uplift twice and oversizes everything after it.
The house's existing loads, from floor area and nameplates
2,400 sq ft (223 m²); 12 kW range; 5,000 VA dryer; water heater, dishwasher, disposal and microwave totalling 8,100 VA; central air 6,000 VA (gas furnace heat); three small-appliance circuits and a laundry circuit
Floor area taken to the outside of the exterior walls, leaving out the garage and open porches, and each appliance's rating read off its own plate rather than assumed from its type. A listing's square footage is often the wrong figure — it may include the garage or stop at the inside face of the walls — and a gas range entered as electric adds 8,000 VA of demand that is not there.
The panel: rating, spaces, and where the free ones are
200 A main, 40 spaces; 24 single-pole and 4 two-pole breakers installed (range, dryer, water heater, air conditioner)
Counted on the panel itself — the label for the bus rating and the number of spaces, the breakers actually installed — and not from the directory card, which is rarely current. What matters is two free spaces one directly above the other in the same column, which is what puts them on opposite legs; counting free spaces without looking at where they sit is how a two-pole breaker turns out not to fit.
Termination temperature ratings at both ends of the circuit
Breaker marked 60/75 °C; charger terminals rated 75 °C
Read on the breaker's label and in the charger's installation manual, where the terminal rating is stated. The mistake is to take the rating from the wire: THHN has 90 °C insulation, but the circuit may only use the ampacity allowed at its lowest-rated termination, and an unmarked terminal on equipment of this size counts as 60 °C.
The route, measured along the path the conduit will take
45 ft (13.72 m): 2 ft (0.61 m) up out of the panel, 11 ft (3.35 m) across the utility-room ceiling and through the wall, 27 ft (8.23 m) along the garage, 5 ft (1.52 m) down to the charger; three 90° bends
Taken leg by leg with a tape along the walls and ceiling, corner to corner, including the rise out of the panel and the drop to the charger. Pacing the garage floor or scaling a plan misses both vertical legs, and it is the route rather than the straight line between the ends that sets the voltage drop, the conductor order and the EMT.
Bender centreline radius
5¼ in (133 mm) on the 3/4 in EMT shoe assumed here
Taken from the shoe of the bender that will make the bends, or from its maker's data — the figure differs between makers, so it is read off the tool rather than assumed. Measuring the inside of a finished bend with a tape gives a smaller number, short by half the conduit's outside diameter, and puts every tangent point in the wrong place.
The takeoff, in order
Each step needs something from the one before it, which is why the order is part of the answer.
Turn the charger's amps into volt-amperes at 240 V
- Needs
- The charger's 48 A continuous rating from the nameplate and the circuit it will run on: 240 V single phase, the two hot conductors of the house's split-phase supply. The service calculation takes the charger in volt-amperes, which are amps times volts whatever the power factor, so the factor is left at 1.
- Produces
- 11.52 kVA — 11,520 VA, the figure the service load calculation in the next step enters for the charger; at a power factor of 1 the page's headline of 11,520 W is the same number. The same page answers a dryer or any other appliance on a 240 V circuit the same way, and three-phase or DC supplies by a choice of field.
Result11,520 W (11.52 kVA) — 48 A × 240 V
Watts, Amps and kVA Calculator (Any Voltage, AC or DC)Check that the service can carry the charger
- Needs
- Step one's 11,520 VA for the charger, and every load the house already has — 2,400 sq ft (223 m²) of floor, the range, dryer, fixed appliances and central air — because the charger is judged against the whole service, not against a spare breaker space.
- Produces
- 192 A by the standard method under the 2023 edition, inside the 200 A service with little to spare; the charger accounts for 60 A of it, counted at the continuous-load uplift on 11,520 VA. The optional method puts the same house at 138 A; by the standard method, the house without the charger calculates at 132 A. The job proceeds without an upgrade or load management, and the before-and-after figures go into the permit file.
Result192 A calculated load (138 A by the optional method) on a 200 A service
Electrical Panel Load Calculator (NEC Service Sizing)Confirm two adjacent spaces for a two-pole breaker
- Needs
- Step two's answer that the service has room, and the panel as it will finish: 40 spaces, the 24 single-pole and 4 two-pole breakers already in it, and the charger's breaker added as a fifth two-pole — spaces are only worth counting once the load calculation says yes.
- Produces
- Six spaces left after the charger's breaker takes two. The count is necessary but not sufficient: the two spaces have to be neighbours on opposite legs of the bus, and a panel whose free spaces are scattered can show six and still need circuits moved before a two-pole breaker will go in. That is checked on the bus itself, with the cover off.
Result6 spaces left — 34 of the 40 used, the charger's breaker included
Electrical Panel Circuit Directory Slot CalculatorSize the breaker for a continuous load
- Needs
- The same 48 A continuous rating that step one turned into volt-amperes for step two, and the pair of adjacent spaces step three found for it — the breaker is chosen only once there is room for it on the service and on the bus.
- Produces
- A 60 A two-pole breaker. The continuous-load rule takes 48 A to exactly 60 A, which is already a standard size, so nothing is rounded up. It is also why chargers of this rating are hardwired rather than plugged in: a 50 A receptacle circuit holds a charger to 40 A under the same rule. The 60 A rating is what the conductor in the next two steps has to be protected by.
Result60 A two-pole breaker — 48 A × 1.25 = 60 A minimum
EV Charger Circuit CalculatorFind the conductor on the conservative column
- Needs
- The 60 A breaker from step four, entered as the circuit load — the conductor is sized to the device protecting it rather than to the 48 A the charger draws, and the continuous-load uplift is already inside that 60.
- Produces
- 4 AWG (21.2 mm²) copper, rated 70 A in Table 310.16's 60 °C column; 6 AWG stops at 55 A in that column and fails. That column is the one NM-B cable is read in, and the one any termination marked 60 °C or not marked at all holds the circuit to. This job runs single THHN conductors in EMT, so the next step checks whether its labels allow the smaller size.
Result4 AWG (21.2 mm²) from the 60 °C column, rated 70 A
Amperage to Wire Gauge CalculatorCheck the smaller conductor against the termination ratings
- Needs
- Step four's 60 A breaker, which step five sized the conductor to, the 75 °C termination ratings read off the breaker and the charger's manual, and 6 AWG THHN's 75 A from the 90 °C column as the starting figure — with no ambient correction for a run kept within the table's 30 °C (86 °F) basis, and no bundling factor for two current-carrying conductors, since the ground never counts.
- Produces
- 75 A after corrections, of which the 75 °C terminations let the circuit claim only 65 A — the 75 °C column's figure for 6 AWG (13.3 mm²). That still clears the 60 A breaker, so 6 AWG THHN is the conductor. Had either termination been marked 60 °C, the answer would have stayed at step five's 4 AWG.
Result75 A corrected; the 75 °C terminations cap the usable figure at 65 A, above the 60 A breaker
Feeder Conductor Ampacity Derating CalculatorCheck the voltage drop over the route
- Needs
- Step six's 6 AWG conductor, the 45 ft (13.72 m) route measured corner to corner from the panel to the charger, and the 48 A the charger actually draws at 240 V — drop is worked at the load current, not at the breaker rating.
- Produces
- 2.12 V lost, 0.88% of 240 V, leaving about 237.9 V at the charger — far inside the 3% the code's informational note suggests for a branch circuit. On a run this short ampacity governs, not drop, so the conductors stay at the size step six allowed. That is the fact the grounding step depends on.
Result2.12 V (0.88% of 240 V; about 237.9 V at the charger)
Wire Gauge Voltage Drop Calculator (Copper or Aluminum, AWG to 1,000 kcmil)Size the equipment grounding conductor
- Needs
- The 60 A breaker from step four, which is what Table 250.122 is indexed on, and step seven's finding that the 6 AWG conductors were not increased for voltage drop — the table row is the whole answer only when nothing was upsized.
- Produces
- No run is printed, deliberately: this calculator's headline is an illustrative scaling number rather than a size, and it says so itself. The size comes from the table row its own note quotes — 10 AWG (5.26 mm²) copper behind a 60 A device. With the conductors at their minimum size, 250.122(B)'s proportional increase does not arise; pulling 4 AWG where 6 AWG would do is what would trigger it. The EMT is a fault path too, but a wire-type ground is pulled so the charger's ground does not depend on every coupling and connector staying tight.
Take off the EMT, bends included
- Needs
- The 45 ft (13.72 m) route from the measurements, less 5¼ in (133 mm) at each end of each of the three 90s — 42 ft 4½ in (12.92 m) of straight conduit between tangent points — and the centreline radius of the 3/4 in bender, the trade size chosen for step six's two 6 AWG conductors and step eight's 10 AWG ground.
- Produces
- 44.4 ft (13.54 m) of EMT: each 90 cuts its corner, so the developed length comes in a little under the corner-to-corner route. That is five 10 ft (3.05 m) sticks. The three 90s use 270° of the 360° allowed between pull points, and the box offsets into the panel and the charger count against what is left; they are not in the length, and the fifth stick's cutoff is what covers them.
Result44.4 ft (13.54 m) of 3/4 in EMT — five 10 ft (3.05 m) sticks
EMT Conduit Bend Length Calculator
The figures
| Step | Calculator | Figure |
|---|---|---|
| Turn the charger's amps into volt-amperes at 240 V | Watts, Amps and kVA Calculator (Any Voltage, AC or DC) | 11,520 W (11.52 kVA) — 48 A × 240 V |
| Check that the service can carry the charger | Electrical Panel Load Calculator (NEC Service Sizing) | 192 A calculated load (138 A by the optional method) on a 200 A service |
| Confirm two adjacent spaces for a two-pole breaker | Electrical Panel Circuit Directory Slot Calculator | 6 spaces left — 34 of the 40 used, the charger's breaker included |
| Size the breaker for a continuous load | EV Charger Circuit Calculator | 60 A two-pole breaker — 48 A × 1.25 = 60 A minimum |
| Find the conductor on the conservative column | Amperage to Wire Gauge Calculator | 4 AWG (21.2 mm²) from the 60 °C column, rated 70 A |
| Check the smaller conductor against the termination ratings | Feeder Conductor Ampacity Derating Calculator | 75 A corrected; the 75 °C terminations cap the usable figure at 65 A, above the 60 A breaker |
| Check the voltage drop over the route | Wire Gauge Voltage Drop Calculator (Copper or Aluminum, AWG to 1,000 kcmil) | 2.12 V (0.88% of 240 V; about 237.9 V at the charger) |
| Take off the EMT, bends included | EMT Conduit Bend Length Calculator | 44.4 ft (13.54 m) of 3/4 in EMT — five 10 ft (3.05 m) sticks |
The waste factors, and why these ends of the ranges
| Material | Applied | Why |
|---|---|---|
| EMT | Whole 10 ft sticks, with the last stick's cutoff as the only allowance | The developed length is 44.4 ft (13.54 m), so the order is five sticks whatever percentage is put on it, and the roughly 5½ ft (1.7 m) of the fifth that the run does not reach covers the two box offsets and one bend made in the wrong place. A second spoiled 90 needs a sixth stick, and on a run this short a spare stick on the truck costs less time than a trip back to the supplier. |
| Conductors — two 6 AWG and one 10 AWG THHN | Route length plus the tails at both ends, per conductor, cut from the reel | Each conductor has to reach from its breaker or bar inside the panel to the charger's terminal block, with enough at both ends to dress and terminate without strain. A conductor cut short cannot be lengthened without a splice in a box the design never had, so the tails are measured at the panel — knockout to breaker position and to the ground bar — rather than guessed. |
| Straps, couplings and connectors | Counted off the route, leg by leg, with no percentage | Couplings follow the joints between sticks, a connector goes at each end, and straps follow the framing and the support spacing the code sets for EMT. None of that scales with length in a way a percentage captures: a short leg next to a box can need as many straps as a long one, and one coupling too few stops the job. |
| The breaker | One, of a type the panel's label lists, and no spare | A two-pole 60 A breaker that physically clips onto the bus is not necessarily one the panel is listed to accept, and the label inside the door names the types it takes. The risk on this line is the wrong part number, not the quantity, so the allowance is a check rather than an extra. |
Where this estimate is most likely to be wrong
Calculated service load
either wayThe standard method puts this house at 192 A and the optional method at 138 A, and which one the inspector accepts is local. On an existing house there is a third route, often lower than either: twelve months of the utility's recorded maximum demand standing in for the calculation under NEC 220.87. The continuous-load uplift on the charger moves the answer as well: some inspectors take 220.57's nameplate figure as the whole calculated load, with no uplift on top, which takes about 12 A off the standard result. Against all of that, any load added since the nameplates were read — a hot tub, a second charger, a heat pump replacing gas — pushes it toward the service rating.
Narrow it by: Asking the inspector which method is accepted, whether the utility's demand history may be used, and how 220.57 is read, all before the permit is drawn, and listing every load that is planned as well as today's.
Conductor size
usually under6 AWG rests on two labels and one assumption. If the breaker or the charger turns out to be marked for 60 °C, or the breaker bought on the day is an older type with no 75 °C marking, the conductor goes up to 4 AWG. The assumption is the ambient: a garage that runs hot in summer takes a correction factor below one, though the 90 °C starting figure leaves room before the result falls to the 60 A breaker.
Narrow it by: Reading the termination marking on the exact breaker being bought and in the manual of the exact charger model, and checking the hottest ambient the run passes through against the correction table.
EMT and fittings
usually underThe length assumes three clean 90s on a clear route. Box offsets at the panel and the charger, a kick around a joist or a duct, and a saddle over a pipe each add developed length the calculator does not count, and a bend made in the wrong place is cut out and lost with the conduit either side of it. Every one of those also spends part of the bend allowance between pull points. The hole through the wall between the utility room and the garage is a line of its own: it has to be sealed around the EMT so the separation between house and garage stays intact, and neither the sealant nor the time is in the takeoff.
Narrow it by: Walking the route with the bender's take-up in mind before the first stick is cut, marking every offset the route needs alongside the three 90s, and asking the inspector what the house-to-garage wall needs around the penetration.
Conductor length
usually underThe route was taken corner to corner along the walls, but the conductors also travel inside the panel to their breaker and bar and inside the charger to its terminal block, and a pull needs a little slack at each end. A conductor that arrives short cannot be stretched; it is replaced or spliced, and the splice needs a box the plan did not have.
Narrow it by: Measuring the tail inside the panel from the knockout to the breaker position and the ground bar, and reading the lead-in length from the charger's manual, before cutting from the reel.
Protection and switching this page does not check
usually underThe parts list holds one two-pole breaker and nothing between it and the charger. Ground-fault protection and a disconnecting means both have their own rules for vehicle charging equipment, which vary with the edition adopted and with how the charger is connected, and none of the calculators here tests them. Where either is required, it is a part the list does not yet contain.
Narrow it by: Reading the charger's installation manual for its protection and disconnect requirements, and confirming the locally adopted edition's rules with the inspector at the permit stage.
Tools this job needs
Frequently asked questions
- What size breaker does a 48 amp EV charger need?
- A 60 A two-pole breaker. Charging is a continuous load, so the circuit is sized at 125% of the charger's 48 A, which comes to exactly 60 A — already a standard size, so nothing is rounded up. By the standard method, the same 60 A is what the charger adds to the house's calculated service load. Units this size are hardwired, because a 50 A receptacle circuit holds a charger to 40 A. On this 45 ft (13.72 m) run the breaker, not the distance, sets the conductor.
- What wire size do I need for a 48 amp charger?
- On this job, 6 AWG (13.3 mm²) copper THHN in EMT, because the breaker and the charger's terminals are both rated 75 °C, where 6 AWG carries 65 A against the 60 A breaker. If either termination is 60 °C or unmarked, or the run is NM-B cable, the answer is 4 AWG (21.2 mm²). Over the 45 ft (13.72 m) route at 48 A the drop is 2.12 V, 0.88% of 240 V. The ground is 10 AWG (5.26 mm²).
- Can a 200 amp panel handle a 48 amp EV charger?
- This one can. For a 2,400 sq ft (223 m²) house with an electric range and dryer, central air with gas heat and four fixed appliances, the NEC standard calculation comes to 192 A with the charger counted at 60 A, and the optional method to 138 A; by the standard method the house without the charger calculates at 132 A. A house nearer the limit can often avoid a bigger service with a listed energy management system that throttles the charger when the house is busy.