**You can transition to a cheaper wiring method indoors.** Assuming U.S. NEC rules, RMC is not required all the way to both panels.

- **EMT (“thin-wall” metal conduit)** is a practical indoor option, including concealed runs in walls and ceilings. Join it to RMC with a listed transition fitting or through a suitable box. You can keep the same conductors throughout. [EMT rules](https://steeltubeinstitute.org/resources/2023-national-electrical-code-nec-changes/), [transition fittings](https://hubbellcdn.com/catalogfull/HES-MULTI-CAT-EN-03988_B.pdf).
- **Electrical PVC conduit** is also generally permitted inside walls and ceilings, subject to physical-damage protection and local amendments. Switching to PVC affects your grounding arrangement. [NEC Article 352 text in NFPA’s development record](https://docinfofiles.nfpa.org/files/AboutTheCodes/70/70_A2022_NEC_P08_SD_PCSubmittals.pdf).

**Your three-wire plan makes grounding particularly important.** For a typical 120/240-volt shed feeder, you need two hots, a neutral, and an equipment-grounding path. Properly connected and bonded RMC and EMT can supply that grounding path, allowing three insulated wires. PVC cannot: if you introduce PVC, provide a grounding conductor and bond the metal portions. A continuous grounding wire alongside the feeder conductors is a straightforward choice. [Steel Tube Institute grounding guidance](https://steeltubeinstitute.org/resources/equipment-grounding-using-steel-conduit/).

For the trench, **IMC is another option to price**: it generally qualifies for the same six-inch cover as RMC. Ordinary buried PVC generally requires 18 inches. Six inches of *cover* means soil above the conduit’s top, so the trench must be deeper than six inches. Special locations can require greater cover; confirm your route with the inspector before buying materials. [Minnesota’s NEC inspection checklist](https://www.dli.mn.gov/sites/default/files/pdf/eli_inspection_checklist2023NEC.pdf).

Use wet-location-rated conductors underground, such as THWN-2. At the shed, keep neutral isolated from the enclosure and grounding bar, and provide the required grounding electrode system; ground rods do not replace the feeder’s equipment-grounding path. [Southwire wire specifications](https://www.southwire.com/wire-cable/building-wire/simpull-sup-sup-thhn-thwn-2-copper/p/20494104), [detached-building grounding guidance](https://www.dli.mn.gov/sites/default/files/pdf/eli_bulletin_multiple_feeders.pdf).