For a house on a 200 A service, NEC 310.12 gives 2/0 AWG copper or 4/0 AWG aluminum, as long as the conductors and the terminals they connect to are rated 75 °C. Neither size reaches 200 A by itself. In the 75 °C column of Table 310.16, 2/0 copper is rated 175 A and 4/0 aluminum 180 A. Both are more than 166 A, and 166 A is all 310.12 asks of a dwelling service, since it sets the minimum at 83% of the rating.
That smaller size has conditions. 310.12 applies to a one-family house, or to one dwelling unit in a two-family or multifamily building, supplied at 120/240 V single phase, with a service or feeder rated 100 to 400 A. The conductors also have to carry the unit's entire load. A 200 A service to a house meets those conditions, and so does a feeder that supplies everything the unit uses. A 200 A feeder from the main panel to a subpanel doesn't, however large the subpanel, because it carries only part of the load. That feeder is sized for the full 200 A.
At the full 200 A, Table 310.16 gives 3/0 copper in the 75 °C column, rated exactly 200 A with no margin. Every other column needs a size larger than 4/0. 4/0 copper is rated 195 A at 60 °C, and 4/0 aluminum is rated 150 A at 60 °C and 180 A at 75 °C. The answer is in kcmil instead. 250 kcmil copper, rated 215 A at 60 °C, covers the 60 °C copper case, and 250 kcmil aluminum, rated 205 A at 75 °C, covers the 75 °C aluminum case. Aluminum limited to 60 °C needs more than 250 kcmil, which is rated only 170 A in that column. Feeders come under NEC Article 215, and a feeder to a detached building also comes under Article 225. Continuous loads on a subpanel count at 125% (215.4(A)(1); 215.2(A)(1) in 2023).
The 2026 NEC added a condition to the 83% rule: Table 310.12(A) may be used only for conductors or cables rated 75 °C or more. Wire limited to 60 °C has to find 166 A in its own 60 °C column. At 200 A that takes copper to 4/0 and aluminum beyond it. The condition is new in 2026, and many areas still enforce the 2023 or 2020 edition. The inspector knows which edition applies where you are.
Service-entrance cable, type SE, is covered by NEC Article 338. Style SER is one style of it, and the cable's printed legend names both. Southwire stocks 4/0 aluminum SER with three 4/0 conductors and a 2/0 ground. Its spec sheet rates that cable 180 A at 75 °C and 205 A at 90 °C, the same values as Table 310.16. So 4/0 aluminum works as a 200 A dwelling service under 310.12, but as a feeder that has to carry the full 200 A it falls 20 A short in the 75 °C column.
Distance seldom changes a 200 A size. At 240 V and the full 200 A, 3/0 copper loses 6.01 V over 200 feet, which is 2.51%. It doesn't reach 3% until about 239 feet one way, so the length table shows 3/0 in the copper 75 °C column at every length. The cells that read "over 4/0" come from ampacity, not from length. The service sizes hold up too. Carrying 166 A for 200 feet, 2/0 copper drops 2.62% and 4/0 aluminum drops 2.72%. The 3% figure comes from an NEC informational note and is a recommendation, not a requirement.
This page doesn't decide whether a home needs 200 A rather than some other rating. That depends on a load calculation under Article 120 of the 2026 NEC (Article 220 in 2023), which is for the electrician and the inspector to settle. The sizes above assume the 200 A rating has already been decided.