RV Amp Draw Calculator: What Can You Run at Once on 30 or 50 Amp?

Pick your service, tick what runs at once, and the calculator tells you whether it holds — in amps against your actual limit, with the start-up surge modelled separately, because that momentary spike is what trips a breaker far more often than the running total does.

On 30 amp you have one 120V circuit and 3,600 watts. On 50 amp you have two 120V legs of 6,000 watts each, and the calculator splits your loads across them, because 12,000 watts total does not mean 12,000 watts available to whichever leg your air conditioner happens to sit on. That distinction is the one most load calculators skip.

What the calculator is doing

Four steps, all of it arithmetic you can check:

1. Amps = watts ÷ 120. Every RV appliance runs at 120V, on both services. A 1,500W air conditioner is 12.5 amps.
2. The running total is everything ticked, added up. On 30 amp that goes against a single 30 amp limit. On 50 amp it is split across two legs of 50 amps each.
3. The start-up moment is the running total plus the worst single surge on your list — the extra current one motor pulls as it starts while everything else is already going. Air conditioners are modelled at 3.5× their running draw for that instant, other compressors at 3×, and a washer/dryer motor at 2×. A soft starter, if you tick it, cuts that extra by 60% — the middle of Micro-Air’s published 50–70%.
4. The comfortable line at 80% of the supply. A breaker is a thermal device: it will carry 95% of its rating for a while and then open on a hot afternoon with nothing having changed. The calculator marks that line and treats anything above it as tight rather than fine.

On the third point, the calculator is deliberately less alarmist than most. A breaker’s instantaneous trip threshold sits many times its rating, so a compressor’s fraction-of-a-second inrush is normally ridden out without complaint — that is why motors work at all. It only warns about the start-up spike when the sustained load has already eaten the thermal margin, above about 70% of the supply. If your running total is comfortable, a big peak figure is not something to act on, and the calculator says so.

The 3,600W and 12,000W figures are not our arithmetic alone — Progressive Industries publishes exactly those as the maximums for its 30 amp and 50 amp EMS units, which is the equipment built for each service.

The surge is the part nobody accounts for

Here is the pattern that produces most “my breaker trips for no reason” posts. Your load is fine. You have 28 amps of a 30 amp supply and it has been running happily for an hour — long enough for the breaker to be thoroughly warm. Then the air conditioner’s compressor cycles back on and briefly pulls several times its running current. The breaker opens.

The important nuance, and the reason the calculator does not flag this on every rig: that same inrush at 15 amps of running load would have been absorbed without complaint. A breaker is a thermal device with an instantaneous trip set many times above its rating, so brief surges are exactly what it is built to tolerate. What it cannot tolerate is a brief surge on top of a sustained load that has already used up its margin. The spike is the trigger; the sustained load is the cause. Three practical consequences:

• Order matters. Start the air conditioner first, let the compressor settle, then run the microwave. Free, and it solves a lot of trips.
• Cycling is worse than continuous. An air conditioner that reaches temperature and cycles is starting repeatedly, so each cycle is another chance to trip. Running it slightly colder and continuously can be more reliable than letting it cycle against a tight supply.
• A soft starter removes the problem rather than managing it. It is the one purchase on this page that changes what you can run, and the calculator only suggests it when your running load fits and the spike is the sole reason you would trip.

On a generator rather than a pedestal the same surge is a sizing question instead of a tripping one, and it is answered from a different document: what size generator an RV air conditioner needs works from Dometic’s published minimum, then subtracts what altitude and heat take off the generator.

30 amp: one circuit, and one big appliance at a time

Thirty amps at 120V is 3,600 watts, in a single circuit. The useful way to think about it is that your air conditioner takes about 1,500W of that and leaves you roughly 2,000W for everything else — which is exactly one heating appliance, not two.

Combination on 30A	Watts	Amps	Verdict
A/C + lights + TV + converter	2,350	19.6	Comfortable
The above + absorption fridge on electric	2,700	22.5	Comfortable
A/C + water heater + lights + TV + converter	3,750	31.3	Over the limit — trips
Everything electric: A/C, water heater, fridge, converter, lights, TV	4,100	34.2	Trips
A/C + microwave + lights + TV	3,350	27.9	Runs — until the A/C compressor restarts
Water heater + microwave + lights + TV, no A/C	3,250	27.1	Fits — this is the trade you are making

The fourth row is the calculator’s starting state, and it is deliberately the most common real configuration: everything switched to electric because shore power is “free”. It is also 4.2 amps past what the supply can give you. The third row shows that the electric water heater alone is enough to do it — which leads to the cheapest fix on this page.

50 amp: two legs, and why balance beats total

A 50 amp supply is not one big circuit. It is two 120V legs at 50 amps each, and your distribution panel assigns some circuits to one leg and some to the other. Each leg tops out at 6,000W.

That means the honest question is not “am I under 12,000 watts?” but “is either leg over 6,000?” Two air conditioners and an electric water heater on the same leg is 4,600W before anything else joins them — fine on paper against a 12,000W total, and uncomfortably close to a single leg’s limit.

The calculator balances your loads as evenly as the arithmetic allows and shows both legs. Your rig’s real split is fixed by its panel and may be worse than that. If you have ever tripped one leg while the other side of the coach carried on working, this is the reason. Worth spending ten minutes with the panel labels once, so you know which side your heavy circuits are on.

The propane trick, which costs nothing

Two of the biggest draws on most rigs do not have to be electric at all:

• The water heater element is about 1,400W — nearly 12 amps, a third of a 30 amp supply. On propane it is essentially zero.
• An absorption fridge on electric is around 350W. On propane, near nothing. On either supply it wants the rig level — Norcold allows its refrigerators 3° side to side, and our leveling block calculator turns that into blocks.

Switching both takes the calculator’s starting configuration from 34.2 amps to 19.6 — from tripping to comfortable, with no purchase and no compromise beyond remembering to flip them. Try it: untick those two rows and watch the verdict change. The heat then comes from the cylinder instead, and our propane calculator shows how many days a cylinder lasts with it.

This is the honest first answer to “what can I run at once”, and it is why the calculator suggests it before it suggests buying anything. If you take away one thing from this page and it is “put the water heater on propane when it is hot”, the page has done its job.

Why voltage sags, and what that has to do with your load

There is a second failure mode that a load calculation does not show, and it is the one that actually destroys equipment.

On a hot afternoon, a campground’s supply sags under the total load of every rig in the park. Your pedestal voltage drops — 108V, sometimes lower — and that has nothing to do with your own consumption. Low voltage is dangerous to motors specifically: an air conditioner compressor fed under-voltage draws more current to do the same work, heats up, and eventually fails. The appliance you would most like to protect is the one most at risk.

A long extension cord takes more off on top of the park’s sag — 5.6 V at 30 amps through a 25 ft shore cord and a 50 ft extension. Our extension cord calculator works it out for your run, and shows why a portable EMS at the pedestal cannot see it.

This is the distinction between the two things people call “a surge protector”:

• A surge protector watches for voltage spikes and clamps them. Useful, cheap, and blind to a sag.
• An EMS monitors voltage continuously and disconnects your rig when it goes out of range, reconnecting when it recovers. That is the feature that matters at a busy park in August.

Both are compared properly in EMS vs surge protector, and the calculator ranks EMS units first for this reason. And buy for your rig’s service, not the pedestal you are visiting: a 50 amp unit adapted down to 30 is a bigger, costlier object delivering exactly 30 amps.

Five ways the sums go wrong

1. Adding up everything you own. The number that matters is what runs simultaneously on a hot afternoon, which is a much shorter list.
2. Using the microwave’s cooking power. A “1,000W” microwave draws about 1,500W from the outlet. That 500W gap has tripped a lot of breakers.
3. Treating 50 amp as one 12,000W circuit. It is two 6,000W legs, and the balance is set by your panel, not by you.
4. Ignoring the converter. It draws hardest exactly when you have just arrived, plugged in, and turned everything on with low batteries.
5. Expecting a surge protector to add capacity. It protects; it does not supply. The only product here that changes what you can run is the soft starter, and only by removing a spike.

The products this points at

Three purchases follow honestly from the calculator, and one of them is usually unnecessary:

Related guides

• 30 amp vs 50 amp RV — the connectors, the two legs, and the adapter misconception, in full.
• Best RV surge protectors — eight units across both services, compared on joules, cutoffs and warranty.
• EMS vs surge protector — the more important question of which type you actually want.
• Why your RV breaker keeps tripping — the diagnostic version of this page, for when the load is not the cause.
• Can you run an RV air conditioner on batteries? — the same air conditioner, the other side of the transfer switch.
• RV battery calculator — the equivalent arithmetic for when you unplug and run off the bank.
• The electrical section collects everything published so far.

For how products on this site are selected and what we do not claim about them, see the editorial policy.

Questions worth answering