Bad framing sags and bad plumbing leaks, but bad wiring burns. I have seen a charred breaker box that started as a confident Saturday of video tutorials and undersized wire. Wiring a tiny house for RV hookups forces one big decision early, thirty amps or fifty, and everything downstream hangs on it.
Amps, panels, and wire gauge all flow from that one choice, and this guide maps the consequences. You will learn what each service level lets you run at the same time, how to size wire and breakers to your actual loads, where the code lines sit, and when to hand panel work to a licensed electrician. Get the electrons right and the house stays standing.
Electricity Is the One System You Cannot Get Wrong
Bad framing sags; bad plumbing leaks; bad electrical burns the house down. Wiring a tiny house for RV hookups means choosing between 30-amp and 50-amp service — a decision that shapes the panel, the wire, and everything you can run at once. This guide covers both, with the sizing math and safety rules.
Safety first: this guide is educational. Electrical work must meet the NEC and local codes, and high-voltage panel work should be done or verified by a licensed electrician. A tiny house on wheels wired wrong is a fire risk at 65 mph.
1. 30-Amp vs 50-Amp: What the Numbers Mean
30-amp service: 120V, single hot leg — 3,600 watts maximum (30A × 120V). One air conditioner OR one electric water heater OR one space heater at a time, plus lights and small loads. The standard for smaller RVs and modest tiny houses. 50-amp service: 120/240V, two hot legs — 12,000 watts maximum (50A × 240V). Run the mini-split, the water heater, the cooktop, and the dryer simultaneously. The standard for larger tiny houses and full-size RVs. The real difference is 3.3× the power — 50-amp is not “a bit more,” it is a different electrical universe.
2. Which Service Does Your House Need?
Do the load calculation: list every electrical device with its wattage, note which run simultaneously, and sum the realistic concurrent load. Choose 30-amp if: propane heats water and cooks, the mini-split is the only big electric load, and total concurrent load stays under 3,000W (leave 20% headroom). Choose 50-amp if: electric water heater, electric cooktop/range, electric dryer, or multiple big loads run together — or if you want future flexibility. The rule: wire for the service you will have in 5 years, not the one you need today. Upgrading from 30A to 50A later means replacing the inlet, feeder, panel, and much of the wiring — build it once.
3. The Inlet: Where Shore Power Enters
The shore power inlet (Marinco-style twist-lock, mounted on the exterior): 30-amp: NEMA L5-30 or TT-30 inlet — 3 wires (hot, neutral, ground), 10 AWG feeder. 50-amp: NEMA 14-50 or CS6364 inlet — 4 wires (two hots, neutral, ground), 6 AWG feeder. Mount the inlet where the cord reaches the pedestal without crossing walkways, protect it with a weatherproof cover, and label it clearly. The inlet is also the first surge point — a whole-house surge protector ($100–200) installed at the panel is cheap insurance against pedestal power spikes.
4. The Panel: Heart of the System
30-amp: a small 120V load center (4–8 spaces — Square D QO or equivalent), single-pole breakers only. 50-amp: a 120/240V load center (12–20 spaces), with both single-pole (120V) and double-pole (240V) breakers. Panel rules: size the panel 25–50% larger than today’s breaker count (empty spaces are future-proofing), use AFCI breakers for bedroom/living circuits and GFCI for kitchen/bath/exterior (code requires it — and it saves lives), label every breaker (the next owner — or the 2 AM troubleshooter — will thank you), and mount the panel where it is accessible but protected (not in the bathroom, not behind the fridge).
5. Wire Sizing: The Gauge Chart
Copper wire (THHN in conduit, or NM-B/Romex where allowed — note: some jurisdictions restrict NM-B in mobile structures; check local code): 15A circuits: 14 AWG (lights, general outlets). 20A circuits: 12 AWG (kitchen outlets, bathroom). 30A feeder (30-amp service): 10 AWG. 50A feeder (50-amp service): 6 AWG. Voltage drop: in a tiny house, runs are short — but the feeder from inlet to panel still matters; keep it under 25 feet or upsize one gauge. The iron rule: the breaker protects the wire — never put a 20A breaker on 14 AWG wire. When in doubt, upsize the wire.
6. Circuit Layout: Planning the Circuits
A typical tiny house circuit map: lighting (1× 15A — the whole house’s lights draw almost nothing with LEDs), general outlets (1–2× 15A or 20A), kitchen outlets (1–2× 20A GFCI — the small-appliance loads live here), bathroom (1× 20A GFCI), mini-split (dedicated 15–20A, per the unit’s spec), water heater (dedicated 20–30A if electric), washer/dryer (dedicated 20–30A if electric). Dedicated circuits for every major appliance — sharing a water heater with the kitchen outlets is how breakers trip at dinner time. Draw the circuit map before pulling a single wire.
7. Grounding and Bonding: The Mobile Difference
A tiny house on wheels has a grounding subtlety: when plugged into shore power, the pedestal provides the ground — bond neutral to ground ONLY at the source (the pedestal/main), never in the tiny house panel (sub-panel rules: neutral and ground separated, bonded only at the main). When running on inverter/generator, the inverter or generator becomes the source — follow its bonding instructions. Get this wrong and you create shock hazards and nuisance tripping. If the words “neutral-ground bond” are unfamiliar, this is the moment to hire the electrician.
8. Off-Grid and Hybrid: Inverter Integration
Many tiny houses run hybrid: shore power when available, inverter/battery off-grid. The integration: a transfer switch (manual or automatic — prevents backfeeding the pedestal, which can kill lineworkers), an inverter/charger (charges batteries from shore power, inverts battery to AC off-grid — Victron MultiPlus is the tiny house standard), and separated loads (critical loads on the inverter sub-panel; heavy loads shore-only). Size the inverter to the realistic off-grid concurrent load (2,000–3,000W covers most tiny houses). The transfer switch is not optional — it is a life-safety device.
Final Considerations
Wire for 50-amp if there is any doubt; protect every wire with the right breaker; separate neutral and ground in the sub-panel; install the transfer switch; and have a licensed electrician review the panel before energizing. Electricity rewards respect and punishes confidence. In a house you tow down the highway, there is no room for “probably fine.”