Tiny House Electrical Load Planner & Wire Guide

Thirty amps or fifty? It sounds like a small decision, but it decides whether your tiny house can run the cooktop and the water heater at the same time — or whether the main breaker trips every time dinner meets a shower. This guide walks through the loads, the panel and the wire sizes behind that choice, then hands you the planner to run your own numbers.

1. At a Glance: Loads, Service Sizes and Wire Gauges

The planner below answers one question — can a standard 30A RV plug handle your appliances, or do you need a 50A split-phase setup? — and it answers it with your actual load list, not a guess. Tick the appliances you plan to install and it totals their draw, shows your load usage as a percentage, recommends a service size for your main breaker panel, and pairs the result with a wire gauge cheat sheet so every circuit gets the right cable. Here is the whole picture at a glance.

The decision on one card: your biggest loads, the 3,600-watt ceiling of a 30A service, and the 12,000 watts a 50A split-phase setup actually delivers.

2. Start at the Panel: What the Planner Decides

Every electrical decision in a tiny house flows back to one grey box: the main breaker panel. It is where shore power enters the house, where it is divided into circuits, and where the main breaker stands guard over the whole system. Choose a panel and service that are too small and the main breaker becomes the most-used switch in the house, tripping whenever two big loads overlap. Choose them well and you never think about the panel again — which is exactly the point.

That is why a tiny house electrical load planner starts with the appliances instead of the hardware. You tick the loads you genuinely plan to live with, the planner totals them against the two service sizes, and its Main Breaker Panel readout answers with a recommended service — or, before you have selected anything, invites you to select appliances to begin. The Load Usage meter then shows what share of that service your list consumes. If you want the wiring-side companion to this planning step, our guide to tiny house electrical wiring for 30-amp vs 50-amp RV hookups walks through how the chosen service is actually wired.

3. Every Appliance Has a Number: Reading the Load List

The planner’s checklist is short, and that is deliberate: in a tiny house, a handful of appliances account for nearly all the power you will ever draw. Each entry carries its watts, its amps and its voltage, because those three numbers together decide both your service size and your circuit plan. The Standard Load — lights, fridge and laptop — sits at roughly 600W and 5A: not the biggest number on the list, but the one that never switches off.

Above it sit the comfort loads. The mini-split draws 1200W at 10A on 120V. The vented washer/dryer combo asks for 1400W at 12A, and the electric water heater 1440W at 12A, both on 120V. The two-burner induction cooktop tops the 120V group at 1800W and 15A — a single appliance drawing three times the entire standard load. Then the list changes character entirely: the standard electric dryer wants 5000W at 24A on 240V, and the whole-house electric tankless water heater simply states its terms — requires 240V, 50A and up. Read the list that way, as two families, and the service decision is already half made.

4. Circuits: Grouping Loads Room by Room

A service size tells you how much power enters the house; circuits decide how it is shared out. Each circuit is one breaker, one cable run and a group of outlets or appliances, and the art of a good panel schedule is grouping loads so that the things you use together do not fight over the same breaker. The planner’s wire cheat sheet hints at the natural groupings: lighting and general outlets on one class of circuit, kitchen and bath on a heavier one, and major appliances on their own.

In practice that means the cooktop does not share a circuit with the water heater, the bathroom outlet that meets a hair dryer gets a circuit of its own class, and the fridge — the one load that must never lose power — is not bundled with anything that trips often. Planning the groups on paper, while the walls are still open studs and cable can be pulled in minutes, is vastly easier than re-grouping after the panel is dressed and the walls are closed. The load list from the planner becomes your circuit list: one row per heavy appliance, and shared circuits only where the combined draw stays modest.

5. 30 Amp or 50 Amp: One Leg vs Two Legs

Here is the fact the planner is built around, stated in its own words as the 50 Amp Myth: a 50 Amp RV service is actually 100 amps total — two 120V legs at 50A each, which is 12,000 watts. A 30 Amp RV service is only one leg: 3,600 watts. So the step from 30A to 50A is not the modest bump the names suggest. It is more than a threefold jump in usable power, and it changes which appliances can coexist in the house.

It also changes what the house can plug into and how it is fed. The planner’s cheat sheet lists the main service cable for a 50A setup as a four-wire cord — hot, hot, neutral, ground — because those two hot legs are the whole story. On 30A, one leg has to carry everything, and the Load Usage meter fills up fast: the standard load, the mini-split, the water heater and the cooktop already add up to more than a 30A service can give. Builders weighing shore power against generating their own will also want to see how much solar power a tiny house needs, because an off-grid system has to cover the same load list from panels and batteries instead.

6. The Big Draws: Cooktop, Water Heater and Dryer

Service size is rarely decided by the small loads. It is decided by simultaneity — by what happens at 6 p.m. when the cooktop is on, the water heater is recovering from a shower and the mini-split is running. Add the planner’s own figures for that moment: 1800W for the cooktop, 1440W for the water heater, 1200W for the mini-split. The total is 4,440W before the fridge, the lights or a single phone charger join in — already beyond the 3,600 watts a 30A service can supply, even though each appliance on its own looks perfectly reasonable.

The dryer and the tankless water heater play in a different league. A standard electric dryer at 5000W and 24A on 240V draws more than an entire 30A service by itself, and a whole-house electric tankless unit demands 240V and 50A or more before it will work at all. Neither is a bad appliance; both are simply appliances that choose your service for you. If either is non-negotiable in your build, the planner’s answer will be 50A — and if you would rather stay on 30A, the vented washer/dryer combo at 1400W on 120V is the list’s built-in compromise.

7. Heating and Cooling Loads: The Mini-Split Factor

Climate control is the load that runs for hours rather than minutes, which makes the mini-split’s modest-looking 1200W and 10A more significant than the raw figure suggests. It is also the flexible load: a mini-split both heats and cools, so for many tiny houses this single line on the checklist replaces separate heating and cooling appliances. Choosing it shapes the rest of the plan, and if you are still comparing cooling options, the tiny house cooling analyzer breaks down how mini-splits compare with window units.

Heating choices interact with the electrical plan more than any other system in the house. Electric resistance heat in the floor, for instance, draws heavily and continuously — the radiant floor heating power analyzer shows what that appetite does to a power budget — while propane or wood heat barely touches the panel at all. Our overview of how to heat a tiny house compares those routes. The planner’s approach keeps it simple: the mini-split stands in for year-round electric climate control at a known, plannable draw, and anything beyond it has to be added to the list honestly.

8. Wire Gauge: Matching Romex to the Circuit

Breakers and cables are a matched pair: the breaker exists to protect the wire, so each circuit’s cable must be sized for the breaker’s rating. The planner’s Wire Gauge Cheat Sheet lays out the pairings it wants you to use. Lighting and general circuits — LED lights, bedroom outlets, fans — run at 15A on 14/2 Romex, the white-sheathed cable. Kitchen and bath circuits, feeding countertop appliances, hair dryers and heaters, step up to 20A on 12/2, the yellow cable. Major appliances — the RV plug, the electric water heater, the dryer — take 30A circuits on 10/2, sheathed in orange. And the 50A main service itself is fed by 6/3, the thick black four-wire cord: hot, hot, neutral, ground.

The colour coding is a gift on a real build. At a glance, anyone opening a wall or the panel can see which cable belongs to which class of circuit, and a yellow run where a white one is expected raises the right question immediately. What matters is the discipline behind the colours: never let a circuit’s breaker outsize its cable. A 20A load on a 15A cable does not trip anything — it simply heats the wire inside the wall, quietly, every time the circuit is used. Match each circuit to the cheat sheet and the panel protects the house exactly as designed.

9. Safety: Undersized Wire Is a Fire Hazard

The planner includes its cheat sheet, in its own words, to prevent fire hazards from undersized wires — and that is not boilerplate. A wire carrying more current than it is sized for does not fail dramatically; it warms up, and it warms the studs, insulation and dust around it, a little more with every hour of overload. The breaker never trips, because from the breaker’s side of the wall nothing is wrong. Undersized wire is the one electrical mistake that hides inside a finished wall.

The other hazards follow the same pattern of small causes and large consequences. A main breaker that trips weekly is not an annoyance to live with — it is the system reporting that the load list and the service size do not match, and defeating it with a bigger breaker on the same cable converts a warning into a risk. Loose terminations at the panel, circuits loaded to their limit as a permanent condition, and a service cord asked to carry a house it was never sized for all belong on the same list. The planner cannot inspect your workmanship, but it removes the most common excuse: not knowing the numbers. Once the loads, the service and the gauges are right on paper, the build has a safe target to hit.

10. Common Load-Planning Mistakes

The first mistake is choosing the service before the appliances — picking 30A because the plug is familiar, then discovering the dryer, the cooktop and the water heater have other ideas. The planner exists to reverse that order: list first, service second. The second mistake is the mirror image: adding up every appliance as if all of them run at once, all day, and oversizing everything for a peak that never happens. The Load Usage meter rewards honesty in both directions — a realistic list, with the heavy loads you genuinely use together.

Third, builders forget the standard load because it looks trivial: 600W is not trivial on a 3,600-watt service, especially when it runs underneath everything else. Fourth, whole-house electric tankless water heating gets specified by habit from conventional houses, where the service behind it is far larger; in a tiny house it is the single most consequential line on the list. And fifth, the electrical plan gets made in isolation from the rest of the build — yet it touches the heating, the water and the way you will park and plug in. Our tiny house utilities guide covers power alongside water and off-grid sewage, and if the house will run from its own system rather than a pedestal, work through sizing your off-grid battery bank with the same load list in hand.

Final Considerations

A tiny house electrical system is not complicated, but it is unforgiving of guesses. The loads are knowable — the planner lists them to the watt and the amp — the two service sizes differ by a factor of more than three, and every circuit has a correct cable waiting in the cheat sheet. Run your real appliance list through the tiny house electrical load planner below, note the recommended service and your load usage, and let those two readouts settle the 30A versus 50A question before a single cable is pulled. If your plan leans off-grid, pair the result with what solar panels cost for a tiny house so the generation side of the budget gets the same honest treatment.

Tiny House Electrical Planner

How to wire a tiny house? This tool solves the biggest headache for DIY electrical work: “Do I need 30 Amp or 50 Amp service?”

It allows users to select their specific appliances (Induction cooktop? Electric tankless water heater? Mini-split?) and instantly visualizes whether a standard 30A RV plug can handle it, or if they need a 50A Split-Phase setup. It also includes a “Wire Gauge Cheat Sheet” to prevent fire hazards from undersized wires.