For 150 amps, we will need quite a *thick* wire. Which wire gauge is needed for 150 amp service? We will look into a 150 amp service wire size at 0 feet. On top of that, we will also calculate the 150 amp wire size for service **50 feet, 100 feet, 150 feet, 200 feet, and up to 500 feet away** from the source.

Here’s the deal:

Figuring out the standard 150 amp wire is easy *(and we’ll show you how to do that)*. Calculating what size wire we need for 150 amps 100 feet away, however, is a bit complex. Here we will have to account for **3%, 5%, or 10% allowable voltage drop**. We will go step-by-step with a manual calculation that is a bit tedious. To simplify thing and help you out, we have prepared these two key resources that makes the calculation much easier, namely:

**150 Amp Wire Size Calculator.**Here you insert wire length, voltage, and allowable voltage drop, and the calculator will determine which gauge wire you need to facilitate 150 amp current immediately.**150 Amp Wire Gauge Charts for**We have calculated wire sizes needed for 150 amp service 50, 100, 150, 200, 300, 400, and 500 feet away at*3%*and*10%*voltage drop.**12V, 120V, and 220V voltages**with an allowable voltage drop of 3%*(1st chart)*and 10%*(2nd chart)*.

Just off the bat:

We can just read the 150 amp wire size (at 0 feet, very important) of a chart. That chart is found in this NEC 310.16 table and specifies the ampacity of differently-sized copper and aluminum wires. Here is the screenshot from that table:

Here we have it (but do note that this is at 0 feet distance, without voltage drop):

- The correctly sized copper wire for 150 amp service is
**1/0 AWG**.*copper*wire - The correctly sized aluminum wire for 150 amp service is
**3/0 AWG**.*aluminum*wire

Now, in most cases, you will have a wire of some length. With longer wires, you have to account for voltage drop, and thus you have to use thicker wires (thicker than 1/0 AWG copper and 3/0 AWG aluminum wires) for 150 amp service at a distance. Let’s see how much thicker wires we need:

### How To Calculate 150 Amp Wire Size For A Service Distance Away? (Example)

Because the wire itself represents a resistance to the flow of 150 amp current, the voltage may drop. The NEC code tells us that there is:

**3%**allowable voltage drop for**branch circuits**.**5%**allowable voltage drop for**feeders and sub-panels**.**10%**allowable voltage drop for non-critical circuits like**general appliances and general lighting**.

*Example:* If we want to run a 240V voltage 200 feet away for 150 amp service, and the allowable voltage drop is 3%, that means we have to use wire with so little resistance (thicker wire) that the voltage will not fall below **232.8V** (240VÃ—0.03 = 7.2V and 240V – 7.2V = 232.8V).

What size wire do we have to use to satisfy this criteria? Here is how we can calculate the voltage drop for the 150 amp service:

**Voltage Drop (Vd) = 2 Ã— L Ã— K Ã— 150 Amps / CM**

Here, the L is 150 amp wire length, K is specific resistivity (12.9 ohms for copper wires, 21.2 for aluminum wires), and CM are circular mils. If we can calculate how many circular mils a wire should have, we can match those circular mils with the AWG or kcmil wire size.

*Case and point:* Let’s express CM from the equation above and calculate it to determine the copper wire size for 240V 150 amp service 200 feet away with an allowable voltage drop of 3% (for branch circuits, 7.2V voltage drop for this example). We put all of this into the equation:

**CM = 2 Ã— 200 Feet Ã— 12.9 Ohms Ã— 150 Amps / 7.2V = 107,500 Circular Mils**

We see that for this circuit, we need a wire with a cross-section area of at least 107,500 circular mils. We can convert that to AWG using this circular mils to AWG conversion chart. Here is the screenshot from that chart with the highlighted correctly sized wire:

We see that we have to upgrade from the standard 1/0 copper wire for 150 amp service to **2/0 copper wire**. This is because we need at least 107,500 circular mils cross-section, and 1/0 AWG has a bit below that (105,531 CM, to be exact). The next wire – 2/0 AWG wire – is sufficiently thick (133,072 circular mils).

*Note:* Keep in mind that voltage drop is more severe at lower voltages. If we have the same situation but at 120V voltage, we should use 250 kcmil copper wire for 150 amp service.

You want to calculate the voltage drop and adequate 150 amp wire size for your calculation. To avoid this manual calculation and make things simple, we have designed a **150 Amp Wire Size Calculator** that does it for you. You insert wire length in feet, voltage, and allowable voltage drop percentage, and the calculator will automatically determine the 150 amp copper wire size.

Below the calculator, you will also find two useful charts. We have calculated the adequate 150 amp wire sizes for 12V, 120V, and 220V voltages, for services at a distance of up to 500 feet, and made two charts: First for a 3% allowable voltage drop and the second for a 10% allowable voltage drop. You can just look at which size wire you need for 150A current there as well.

Here’s the calculator:

## 150 Amp Wire Size Calculator (Accounted For Voltage Drop)

Here is an example that illustrates how to use this calculator:

Let’s say you want to run a 150 amp service to a sub-panel 400 feet away. The voltage is 120V and the allowable voltage drop for sub-panels is 5%. Slide the 1st wire length slider to ‘400’, 2nd voltage slider to ‘120’, and the 3rd voltage drop percentage slider to ‘5’. Here is the result:

For this 150 amp service, you need a **300 kcmil copper wire**.

*Note:* This calculator accounts for voltage drop very well. However, keep in mind that you need at least 1/0 AWG copper wire for a 150 amp circuit since it has 150A ampacity. If the calculator (at low distances) gives you a thinner wire size, default to 1/0 AWG copper wire.

Here are the all-encompassing 150 amp wire size charts at a distance for 3% and 10% allowable voltage drop:

## 150 Amp Wire Gauge Source 0-500 Feet Away (3% Allowable Voltage Drop)

Wire Length (3% Vd): |
150 Amp Wire Size At 12V: |
150 Amp Wire Size At 120V: |
150 Amp Wire Size At 220V: |

0 Feet | 1/0 AWG Copper Wire | 1/0 AWG Copper Wire | 1/0 AWG Copper Wire |

50 Feet | 600 kcmil Copper Wire | 1/0 AWG Copper Wire | 1/0 AWG Copper Wire |

100 Feet | 1250 kcmil Copper Wire | 2/0 AWG Copper Wire | 1/0 AWG Copper Wire |

150 Feet | 1750 kcmil Copper Wire | 3/0 AWG Copper Wire | 1/0 AWG Copper Wire |

200 Feet | 2 Or More Wires | 250 kcmil Copper Wire | 2/0 AWG Copper Wire |

300 Feet | 2 Or More Wires | 350 kcmil Copper Wire | 4/0 AWG Copper Wire |

400 Feet | 2 Or More Wires | 500 kcmil Copper Wire | 250 kcmil Copper Wire |

500 Feet | 2 Or More Wires | 600 kcmil Copper Wire | 300 kcmil Copper Wire |

We see that at low voltages (12V), we quickly need very thick wires. For example, if we want to run a **100 feet wire** for 150 amp service at a **3%** allowable voltage drop, we need:

**1250 kcmil copper wire**for**12V**circuit.**2/0 AWG copper wire**for**120V**circuit.**1/0 AWG copper wire**for**220V**circuit.

We see that at 100 feet away, the 220V 150 amp wire size stays the same – 1/0 AWG copper wire. At 120V, we have to use a thicker 2/0 AWG copper wire, and at a 12V DC current, we have to use a very thick 1250 kcmil copper wire.

Let’s look at the 10% allowable voltage drop chart as well:

## 150 Amp Wire Gauge Source 0-500 Feet Away (10% Allowable Voltage Drop)

Wire Length (10% Vd): |
150 Amp Wire Size At 12V: |
150 Amp Wire Size At 120V: |
150 Amp Wire Size At 220V: |

0 Feet | 1/0 AWG Copper Wire | 1/0 AWG Copper Wire | 1/0 AWG Copper Wire |

50 Feet | 3/0 AWG Copper Wire | 1/0 AWG Copper Wire | 1/0 AWG Copper Wire |

100 Feet | 350 kcmil Copper Wire | 1/0 AWG Copper Wire | 1/0 AWG Copper Wire |

150 Feet | 500 kcmil Copper Wire | 1/0 AWG Copper Wire | 1/0 AWG Copper Wire |

200 Feet | 700 kcmil Copper Wire | 1/0 AWG Copper Wire | 1/0 AWG Copper Wire |

300 Feet | 1000 kcmil Copper Wire | 1/0 AWG Copper Wire | 1/0 AWG Copper Wire |

400 Feet | 1500 kcmil Copper Wire | 2/0 AWG Copper Wire | 1/0 AWG Copper Wire |

500 Feet | 1750 kcmil Copper Wire | 3/0 AWG Copper Wire | 1/0 AWG Copper Wire |

We see that a 10% allowable voltage drop is less restrictive. As we can see, we will have to use thicker wires at 12V voltage. At 120V and 220V, we can use **1/0 AWG copper wire** for up to 300 feet distance away and up to 500 feet distance away, respectively.

Hopefully, you now have a good understanding of correctly sizing 150 amp wires by, very importantly, accounting for voltage drop at a distance. Using the calculator above and these charts, you are very well equipped to figure this out yourself. If you need any help, do use the comment section below, give us some figures, and we will help you figure out the correctly sized 150 amp wire for your setup.

I am going to replace the breaker box in existing 2 car garage with an apartment upstairs. Current breaker box only has 10 slots. Going to run wire underground from the pole to the breaker box approximately 40 feet away. Garage has a 220 air compressor, 220 water well pump, electric stove / oven and will possibly add a 220 AC window unit at a later date.

3 questions;

Would a 150 amp box be big enough for this application?

What size wire would be required?

If a 200 amp box is required what sized wire would be needed?

Follow on question â€“ I my examples above I asked about 150 and 200 amp breaker boxes. Would the amperage per wire be roughly 1/2 because there are going to be 2 wires carrying it?

Thanks

Chuck

Hi Chuck, alright, the key here is to add up all the wattages. Quite difficult in your case, since you have an air compressor, water well pump, stove, and unknown 220 AC window unit.

Now, the 150 amp breaker can facilitate 120A current (80% breaker rule). At 220V, you will have a combined power output of 120A Ã— 220V = 26,400 watts. That’s quite a lot; if each of the 4 appliances runs on about 6,000 watts or less, the 150 amp box will be enough. That’s how we think about these problems.

For wires, you need to check this copper wire ampacity chart. For example, 1 AWG copper wire has 130A ampacity; this is more than 120A that you would need a wire to handle if you have 150A breakers. If you are using 2 wires, you can use thinner wires; 6 AWG wire has 65A ampacity, so two 6 AWG wires have a combined capacity of 130A.

This is how you can think about all of this. Hope it helps.