Does your space heater need a dedicated circuit?
It will depend on how your home is wired and what space heater you use or plan to use.
So there’s no yes or no answer to the question.
Where you live, how old your home is, and the type and wattage of your space heater all play a part in the equation.
15 or 20-Amp Circuits
First up, most newer homes in North America will be wired using a combination of 15 or 20-amp circuits.
However, it’s common to see 15-amp receptacles on a 20-amp circuit, where the amp value is the intensity of the current.
But you will never find a 20-amp receptacle on a 15-amp circuit.
If you’re not sure what receptacles you have, a 20-amp receptacle is slightly different from a 15-amp receptacle.
A 20-amp receptacle will take a three-prong cord, however, the upper left slot looks like a capital T on its side.
Neither receptacle looks anything like the receptacles in the UK.
When plugging in any type of appliance, it’s important to understand if your outlet is rated at 15 amps or 20 amps.
This is because the amperage of your outlet should never exceed the amperage of the circuit.
And the wattage of your appliance should never exceed what your outlet and circuit can handle.
Unless your home was built within the last decade or so, there’s a good chance it has 15-amp receptacles — receptacles that are not sufficient for the electrical needs of many modern households.
A 15-amp circuit is the perfect choice for lighting, but isn’t enough for some small kitchen appliances, forget about the energy needs of a space heater.
While, in theory, a 15-amp circuit is capable of handling up to a maximum of 1800 watts, the National Electrical Code (NEC) states that the allowable wattage of a circuit is 80% of its total capacity.
That means that instead of 1800 watts, your breaker is capped at 1440 watts.
Meaning you cannot run a heater that uses 1500 watts on that circuit.
Well, you could, but only on the lower settings.
Why does that 80% number matter?
Because if your home burns down because you’ve overloaded the circuit, you won’t be covered by insurance since you’re not operating your appliances within legal, Electrical Code, guidelines.
Overloaded Circuit Warning Signs
If you’re currently using a space heater on a shared circuit and wondering if it should be on a dedicated one, here are some warning signs of an overloaded circuit.
- If you’re feeling like your home is possessed, with lights in a few specific rooms always flickering, blinking, or dimming seemingly on their own, this is a classic sign of an overloaded circuit. But that’s not all.
- You should pay attention to the most obvious sign, which is a breaker always tripping or fuse blowing. This is something of a defense mechanism—it’s your system shutting itself down before your wiring overheats and starts a fire.
- Other warning signs are sizzling or buzzing sounds, discolored or cracking outlets/receptacles, hot-to-the-touch switches or switch plates, getting an electrical shock when plugging something in, or a burning odor that you can’t seem to source.
If any of that is happening while you’re running your space heater, unplug it immediately.
The NEC’s 80% Rule
So why is there an 80% maximum load rule on circuits?
First, the rule only applies to continuous loads.
The NEC defines a continuous load as a load — such as an appliance — that will run uninterrupted for three hours or more.
So if you plan to use a space heater for more than three hours, the 80% rule applies.
Overloaded circuits are the major cause of residential fires, so the rule is a safety measure. Breakers are another safety measure.
Deliberately plugging in something that you know exceeds the load of a circuit and that you know will trip your breaker, is dangerous.
Eventually, the breaker will stop working as it was designed to work, allowing the circuit to overload, and eventually overheat the insulation surrounding your wiring.
This is a fire hazard.
When You Need a Dedicated Circuit for a Space Heater
To some extent, it will depend on the wattage of your space heater.
Lower-wattage models will draw fewer amps, so a space heater that draws only 200 to maybe 700 or 800 amps could easily work on the same circuit as other low-wattage appliances or lights.
The following is a list of space heaters with their wattage and amperage.
Use it to determine what you can use on a 15 or 20-amp circuit.
But keep in mind that you can only use 80% of the maximum rated draw.
So a 15-amp circuit can only have 12 amps in total on it and a 20-amp circuit can have 16 amps in total.
|Space Heater Wattage||Watts to Amps (apprx)|
A 1500-watt space heater, which is the most common size, is already too big—on its own—for a 15-amp circuit.
But you could put it on a 20-amp circuit and still add a few things thing to the same circuit.
Appliances That Need a Dedicated Circuit (Maybe)
If math isn’t your thing—and I hear you, if that’s the case—you probably don’t want to or can’t figure out how to determine what household appliances should be on a dedicated circuit.
Here is a list of items that would typically need a dedicated circuit.
I say typically, because all things aren’t created equal, and there may be times a toaster oven or space heater won’t need a dedicated heater.
In those cases, sorry.
You’ll need to do your math.
Some of these will be obvious but in the hopes of creating a complete list, we’re adding them anyway.
Note: Each of the following assumes that the appliance is running in a standard North American home using 120-volt circuits.
A normal sized refrigerator — the kind with the freezer on top — will use about 725 watts of power, which is the equivalent of just over 6 amps, on average.
Some data says that the typical refrigerator in the US uses about 7% of the household’s energy.
Since 6 amps is just an average, a refrigerator could use 10 or more amps depending on its make, model, and age.
Some smaller models may use as little as 400 watts while high-end, larger models can use up to 1300 watts.
Does a refrigerator need a dedicated circuit?
If it’s a smaller model that operates in the average 6-amp range, a dedicated circuit is not needed.
However, it’s a good idea to have one since many small kitchen appliances do use a high number of amps.
Depending on whether you have an electric or gas range the electrical requirements differ.
A gas stove will typically need a dedicated 15-amp circuit at least, although sometimes it may need 20 amps.
Electric stoves require significantly more electricity, typically a circuit that’s rated between 50 and 60 amps, especially if you have a microwave on the same circuit.
Whether or not your microwave requires a dedicated circuit depends entirely on how powerful it is.
Small, compact microwaves may use as little as 600 to 800 watts, while medium to large sized microwaves will be in the range of 800 to 1000 watts.
Small microwaves won’t need a dedicated circuit since they are using less than 7 amps.
So they can easily share a circuit with other low wattage kitchen appliances.
However, a 1,000 watt microwave is going to use around 14 amps.
This means it can’t be plugged into a 15-amp circuit, since it will exceed 80% max usage.
A 20-amp circuit will have a 16-amp cap, meaning very little else could be added to the circuit—but you could add to it.
So depending on the size of your microwave, and whether or not you’re using a 15 or 20-amp circuit, you may or may not need a dedicated circuit for a microwave.
Most dishwashers use about 1,200 watts, translating into between 10 and 12 amps.
However, it’s not uncommon for many models to need up to 15 amps.
A 15-amp circuit maxes out at 12 amps, so there’s a good chance your dishwasher may require a dedicated circuit.
Washer / Dryer
Most newer homes will have a 20-amp circuit for the washing machine and a dedicated 30-amp circuit for the dryer.
The average washing machine uses up to 20 amps per load of laundry while a dryer uses 30 amps per load.
The general rule is smaller appliances typically won’t need a dedicated circuit unless they produce heat.
However, with the exception of something like a countertop convection oven, you shouldn’t need a dedicated circuit.
Having said that, you may find that plugging in a small appliance trips your breaker.
In that case, you should add up how many amps you’re running on that circuit, and remove something.
Can You Plug Your Space Heater into an Extension Cord?
This is another “it depends” situation.
It depends on your extension cord and your space heater.
You should be okay if you use a regular indoor, light-duty extension cord and a low-wattage space heater.
Extension cords are rated by amps, and the amp rating should always be higher than the amp rating on the device or appliance you want to plug in.
If not, you can damage the appliance and or the device and potentially start a fire.
And in some cases, the longer the cord, the higher the voltage drop—meaning longer cords can pass less amperage.
So a 16-gauge light-duty extension cord is rated at 13 amps at 25 feet but only 10 amps at 100 feet.
If you need to plug a space heater into an extension cord, check its rating against the amperage of the heater and its length.
You can use the following as a reference, just remember that the higher the gauge number, the lower of amp rating.
|Extension Cord Amp Ratings|
|Length in Ft||16 AWG||14 AWG||12 AWG||10 AWG|
|25||13 AWG||15 AWG||15 AWG||30 AWG|
|50||13 AWG||15 AWG||15 AWG||20 AWG|
|100||10 AWG||13 AWG||15 AWG||20 AWG|
* AWG = American Wire Gauge
Unfortunately, the higher the wattage of your space heater, the greater chance you’ll need to use one of those bright orange or yellow outdoor, heavy-duty rated extension cords—assuming you plan to use one.
Like so many other things in heating, air conditioning, and power consumption, so much depends on several variables.
At the end of the day, whether or not your space heater will need a dedicated circuit falls into that category.
Is the outlet you plan to plug into on a 15 or 20-amp circuit?
If it’s on a circuit that’s only rated at 15 amps but, according to the Electrical Code can only be safely used at 80%, you can’t put a 1500-watt space heater on it, whether dedicated or not.
You could put a 1400-watt space heater on a 15-amp circuit, but it would probably need to be a dedicated circuit.
At 11.67 amps, it would be just under the 12 allowable amps on the circuit.
Look for something in the range of 1000 watts, and you won’t need to worry about dedicated circuits.
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