OP, I agree with MikeRTX that most people really don't need the full 48 amp charging.
However, I think when running 200 feet of conduit you might find the cost is not too much different for a 30 amp circuit compared with a 60 amp circuit as the labor and profit is probably 3/4th or more of the cost.
But I just ran this circuit on Mike Holt's Electrical Toolbox app for continuous loads of 48 amps and 40 amps and it says you can run a 48 amp load on #6 CU or a #4 AL circuit about 350 feet and a load of 40 amps on #8 CU or #6 AL about 250 feet without suffering unacceptable voltage drop.
Going down to a 32 amp load requires #8 CU or AL and 24 amps requires #10 CU both of which can run more than 200 feet according to the app.
Note that it also says even # 8 CU should be installed in 3/4" conduit as well that #6 CU or AL should be installed in 3/4" conduit and #4 AL should be installed in 1" conduit. Only when getting down to #10 does the app recommend 1/2" conduit.
As an electrical engineer and with my past dealings with electricians, I think it will serve you best if you are as educated about this as possible since this will be an expensive undertaking, so you know what should be done to do the job. But I would not tell them how to do their job, most will not take kindly to that and won't really listen to a layman anyway. Just be informed when you speak with them.
Here is the 48 amp engineering details from that app:
USER INPUTS
System/Volts: Single Phase, 240 Volts
Circuit Type: Branch Circuit
Circuit Protection Size: 60 Amperes
Continuous Load: 48 Amperes
RESULTS COPPER
1. Circuit Protection Size: 60 Amperes
2. Conductor Size: 6 AWG, rated 65A at 75°C
3. Equipment Grounding Conductor: 10 AWG
4.Maximum Circuit Length: 355 Feet
5. Raceway Size:¾ Inch
6. Maximum Circuit Continuous Load:48 Amperes
7. Maximum Circuit VA:11,520VA
RESULTS ALUMINUM
1. Circuit Protection Size: 60 Amperes
2. Conductor Size: 4 AWG, rated 65A at 75°C
3. Equipment Grounding Conductor:8 AWG
4. Maximum Circuit Length: 344 Feet
5. Raceway Size: 1 Inch
6. Maximum Circuit Continuous Load: 48 Amperes
7. Maximum Circuit VA: 11,520 VA
CALCULATIONS and NOTES
1. Protection Size [210.20(A), 240.4, and 240.6(A)]
2. Conductor Size (up to six conductor bundle) [110.14(C)(1)(a)(3)/(b)(1), 210.19(A)(1)(a), 240.4, 310.15, and Table 310.15(B)(16)]
3. Equipment Grounding Conductor Size [250.122]
Sized to the 60A rating of the protection device.
4. Maximum Circuit Length [110.3(B)]
Length limited to ensures the voltage is within 90% of the rated voltage.
5. Raceway Size [Chapter 9, Table 1]
Based on a raceway at 40% fill, with an equipment grounding conductor.
6. Maximum Continuous Load [210.19(A)(1)(a) and 210.20(A)]
Maximum continuous load not to exceed 80% of the circuit protection and conductor ampacity.
60A x 80% = 48A
7.Maximum Circuit Continuous VA: Circuit Voltage x Circuit Amperes 240V x 48.00A x 1 = 11,520 VA
Application Notes
1. Circuit Distance:
a. The circuit length in the app uses the following formula:
i. Single‑Phase: D = (Cmil × VD)/(2 × K × I)
ii. Three‑Phase: D = (Cmil × VD)/(1.732 × K × I)
b. Distance (D): The distance of the circuit or the length of the circuit conductors.
c. Circular Mils (Cmil): The circular mil area of the circuit conductor as listed in the NEC Chapter 9, Table 8.
d. Voltage Drop (VD): The voltage drop of the branch circuit is based on the 110.3(B) of the NEC, which requires that the operating voltage at utilization equipment to be in accordance with manufacturer instructions. Manufactures typically adopt ANSI C84.1, which specifies that the voltage at utilization equipment must be within 90 percent of the nominal system voltage. The app assumes a 3 percent feeder voltage drop, resulting in a 7 percent branch circuit voltage drop.
e. Constant (K): A value of 12.90 ohms is used for copper and 21.20 ohms for aluminum. These values represents the resistance for a 1,000 circular mils conductor that’s 1,000 ft long, at an operating temperature of 75ºC.
f. Current (I): The current of the circuit is the actual load at 100 percent. According to the NEC, conductors are sized to 125 percent of the load continuous loads, electric space heating, motors, electric vehicles, etc. However, this 125 percent factor has nothing to do with determining the distance (length) of the circuit.
2. Conductor Sizing (Commercial):
a. Conductors are sized based on the following factors:
i. Insulation - THHN, THWN, and THWN-2 (90°C).
ii. Terminals – Conductors are sized to 75°C terminals [110.14(C)(1)(a)(3) and 110.14(C)(1)(b)(2).
iii. Load – The load is considered continuous and a 125% continuous load factor is applied [210.19(A)(1)].
iv. Neutral – Where a neutral is used (slash rated circuits), the neutral is considered current carrying (50 percent or more of the load is considered nonlinear) [310.15].
v. Ampacity Adjustment – For three-phase four-wire circuits, the ampacity of the conductors are adjusted by a multiplier of 80 percent [310.15].
3. Conductor Sizing (Residential):
a. Conductors are sized based on the following factors:
i. Insulation - THHN, THWN, and THWN-2 (90°C)
ii. Terminals – Conductors are sized to 75°C terminals [110.14(C)(1)(a)(3) and 110.14(C)(1)(b)(2), except Type NM Cable, which is sized to 60°C [334.80].
iii. Load – The load is considered noncontinuous.
iv. Neutral – The neutral conductor is not considered a current carrying conductor [310.15].
v. Ampacity Adjustment – There is no ampacity adjustment, since there are not four or more current carrying conductors.
4. Raceway Sizing:
a. Raceways are sized to provide a little more space than the NEC minimum requirement. This is accomplished by sizing all circuit conductors, including the neutral and equipment grounding to the same size as the circuit conductors. The conductor insulation is based on THHN, THWN, and THWN-2 and the raceway is considered Schedule 40 PVC.
i. Single-phase two-wire circuits are sized to three full size circuit conductors.
ii. Single-phase three-wire circuits are sized to four full size circuit conductors.
iii. Three-phase three-wire circuits are sized to four full size circuit conductors.
iv. Three-phase four-wire circuits are sized to five full size circuit conductors.
And here is the 40 amp engineering from the app:
USER INPUTS
System/Volts: Single Phase, 240 Volts
Circuit Type: Branch Circuit
Circuit Protection Size: 50 Amperes
Continuous Load: 40 Amperes
RESULTS COPPER
1. Circuit Protection Size: 50 Amperes
2. Conductor Size: 8 AWG, rated 50A at 75°C
3. Equipment Grounding Conductor: 10 AWG
4.Maximum Circuit Length: 268 Feet
5. Raceway Size:¾ Inch
6. Maximum Circuit Continuous Load:40 Amperes
7. Maximum Circuit VA:9,600VA
RESULTS ALUMINUM
1. Circuit Protection Size: 50 Amperes
2. Conductor Size: 6 AWG, rated 50A at 75°C
3. Equipment Grounding Conductor:8 AWG
4. Maximum Circuit Length: 259 Feet
5. Raceway Size: ¾ Inch
6. Maximum Circuit Continuous Load: 40 Amperes
7. Maximum Circuit VA: 9,600 VA
CALCULATIONS and NOTES
1. Protection Size [210.20(A), 240.4, and 240.6(A)]
2. Conductor Size (up to six conductor bundle) [110.14(C)(1)(a)(3)/(b)(1), 210.19(A)(1)(a), 240.4, 310.15, and Table 310.15(B)(16)]
3. Equipment Grounding Conductor Size [250.122]
Sized to the 50A rating of the protection device.
4. Maximum Circuit Length [110.3(B)]
Length limited to ensures the voltage is within 90% of the rated voltage.
5. Raceway Size [Chapter 9, Table 1]
Based on a raceway at 40% fill, with an equipment grounding conductor.
6. Maximum Continuous Load [210.19(A)(1)(a) and 210.20(A)]
Maximum continuous load not to exceed 80% of the circuit protection and conductor ampacity.
50A x 80% = 40A
7.Maximum Circuit Continuous VA: Circuit Voltage x Circuit Amperes 240V x 40.00A x 1 = 9,600 VA
Application Notes
1. Circuit Distance:
a. The circuit length in the app uses the following formula:
i. Single‑Phase: D = (Cmil × VD)/(2 × K × I)
ii. Three‑Phase: D = (Cmil × VD)/(1.732 × K × I)
b. Distance (D): The distance of the circuit or the length of the circuit conductors.
c. Circular Mils (Cmil): The circular mil area of the circuit conductor as listed in the NEC Chapter 9, Table 8.
d. Voltage Drop (VD): The voltage drop of the branch circuit is based on the 110.3(B) of the NEC, which requires that the operating voltage at utilization equipment to be in accordance with manufacturer instructions. Manufactures typically adopt ANSI C84.1, which specifies that the voltage at utilization equipment must be within 90 percent of the nominal system voltage. The app assumes a 3 percent feeder voltage drop, resulting in a 7 percent branch circuit voltage drop.
e. Constant (K): A value of 12.90 ohms is used for copper and 21.20 ohms for aluminum. These values represents the resistance for a 1,000 circular mils conductor that’s 1,000 ft long, at an operating temperature of 75ºC.
f. Current (I): The current of the circuit is the actual load at 100 percent. According to the NEC, conductors are sized to 125 percent of the load continuous loads, electric space heating, motors, electric vehicles, etc. However, this 125 percent factor has nothing to do with determining the distance (length) of the circuit.
2. Conductor Sizing (Commercial):
a. Conductors are sized based on the following factors:
i. Insulation - THHN, THWN, and THWN-2 (90°C).
ii. Terminals – Conductors are sized to 75°C terminals [110.14(C)(1)(a)(3) and 110.14(C)(1)(b)(2).
iii. Load – The load is considered continuous and a 125% continuous load factor is applied [210.19(A)(1)].
iv. Neutral – Where a neutral is used (slash rated circuits), the neutral is considered current carrying (50 percent or more of the load is considered nonlinear) [310.15].
v. Ampacity Adjustment – For three-phase four-wire circuits, the ampacity of the conductors are adjusted by a multiplier of 80 percent [310.15].
3. Conductor Sizing (Residential):
a. Conductors are sized based on the following factors:
i. Insulation - THHN, THWN, and THWN-2 (90°C)
ii. Terminals – Conductors are sized to 75°C terminals [110.14(C)(1)(a)(3) and 110.14(C)(1)(b)(2), except Type NM Cable, which is sized to 60°C [334.80].
iii. Load – The load is considered noncontinuous.
iv. Neutral – The neutral conductor is not considered a current carrying conductor [310.15].
v. Ampacity Adjustment – There is no ampacity adjustment, since there are not four or more current carrying conductors.
4. Raceway Sizing:
a. Raceways are sized to provide a little more space than the NEC minimum requirement. This is accomplished by sizing all circuit conductors, including the neutral and equipment grounding to the same size as the circuit conductors. The conductor insulation is based on THHN, THWN, and THWN-2 and the raceway is considered Schedule 40 PVC.
i. Single-phase two-wire circuits are sized to three full size circuit conductors.
ii. Single-phase three-wire circuits are sized to four full size circuit conductors.
iii. Three-phase three-wire circuits are sized to four full size circuit conductors.
iv. Three-phase four-wire circuits are sized to five full size circuit conductors.