Is 20 Amps Enough for a Garage? (One Helpful Guide!)
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Is 20 Amps Enough for a Garage?
Are you planning the wiring of your new garage? You will need answers to a few questions. For example, what should be the size of the subpanel and the main breaker for the garage? You will also need to know if 20 amps branch circuits are enough for a garage?
A 20 amp branch circuit is enough for most garages as it can safely support a maximum continuous electrical load of 1920 Watts.
A single 20 amps branch circuit can safely support
- up to 3 average sized Garage Door Openers (GDO), OR
- 29 light fixtures rated at 65W, OR
- 10 outlets / receptacles.
Unless you have equipment or appliances in your garage that are rated at higher than 1920 Watts, 20 amps branch circuits are enough for your garage.
The calculations for what you can or can not run on a 20 amps branch circuit is not very complicated. Once you know the way to figure that out, you can do the calculations for your own garage and not go by general calculations.
How Much Can You Run on 20 Amps?
Current (Amps), Power (Watts) and Voltage (Volts) are related to each other by a rather simple formula (Ohm’s Law) as under:
Power (Watts) = Current (Amps) X Voltage (Volts)
The NEC code requires that for Maximum Continuous Electrical Load you must incorporate a “Safety Factor” of 80%. The formula then gets modified to:
Power (Watts) = Current (Amps) X Voltage (Volts) X 80%
Since garage branch circuits in the US are 120V, a 20 amps branch circuit can safely support a Maximum Continuous Electrical Load of 120 X 20 X 0.80 = 1920 W.
How Many Amps Does a Garage Door Opener Need?
The power rating of a Garage Door Opener (GDO) is expressed in horsepower (hp). Garage Door Openers with a power rating of 0.5 hp are most common. Heavier doors, such as those made from real wood may require a 0.75 hp Garage Door Opener.
Garage Door Openers with higher ratings such as 1.0 hp or 1.25 hp are also available for very large garage doors (e.g. RV Garages). As one horsepower is equal to 746 Watts the table below can help you calculate the wattage of a Garage Door Opener.
|Horsepower Rating (hp)||Power Rating (Watts)|
|0.50 hp||373 W|
|0.75 hp||560 W|
|1.00 hp||746 W|
|1.25 hp||933 W|
Add to the above the power rating of the Garage Door Opener light bulbs. The maximum wattage is 100W for incandescent bulbs and 10W for LED bulbs. (Does anyone still use incandescent bulbs?)
So a 20 amps branch circuit can easily run up to 3 Garage Door Openers, with LED bulbs, and a power rating of 0.75 hp each.
For a typical 2-car, 2-door garage I would suggest that you run a 20 amps branch circuit for 4 to 6 GFCI receptacles (thumb rule 1 receptacle = 1.5 amps) and the 2 Garage Door Openers (each with 0.5 hp rating and 10 W LED bulb).
The load would draw less than 16 amps (which is within the safety factor of 80% of 20 amps).
How Many LED Lights Can Run Off a 20 Amp Circuit?
You can run 32, 60 W incandescent light fixtures or 192, 10 W LED light fixtures on a 20 amp circuit.
LED light bulbs rated at 10 W have the same brightness level (650 lm) as that of a 60 W incandescent light bulb.
The brightness level from 32, 60 W incandescent light bulbs would be 20,800 lm, which is just right for a 2-car garage. However, the brightness level from 192, 10 W LED light bulbs would be 124,800 lm. That is way too high! A garage does not require so much brightness and so many LED lights!
As a thumb rule, the brightness level in the parking & storage area should be 30 to 40 lm per square foot. The brightness level in the workshop area needs to be higher at 70 to 80 lm per square foot.
A standard single garage is 240 ft.² (12’ X 20’). You need between 12 – 16, 10 W LED light fixtures. With a 10 W, 650 lm LED light bulb in each fixture, you will get a brightness level of 7,800 – 10,400 lm in the garage.
A larger 2-car garage, that is 480 ft.² (24’ X 20’) and has a small DIY workshop area, will need 8 – 12, 10 W LED light fixtures in the workshop area and 16 – 24, 10 W LED light fixtures in the parking & storage area. That is a total of 24 – 36, 10 W LED light fixtures.
With a 10 W, 650 lm LED light bulb in each fixture, you will get a brightness level of 5,200 – 7,800 lm in the workshop area and 10,400 – 15,600 lm in the remaining area meant for parking & storage.
As long as you use LED light fixtures & bulbs, a 20 amp branch circuit can more than handle the lighting requirements of your garage.
NOTE: You would actually use a 15 amp (not a 20 amp) branch circuit for recessed garage lights!
What Is the Maximum Number of Receptacles in a 20 Amp Circuit?
The NEC code does not place a limit on the maximum number of receptacles that can be in a 20 amp circuit.
The reason you can put any number of receptacles in a 20 amp circuit is because a receptacle by itself does not draw any current. The receptacle only draws current when an appliance or power tool is plugged into it.
It is highly unlikely that you will use all the receptacles in a single 20 amp circuit simultaneously. The number of receptacles in a 20 amp circuit really depends on your need for convenience and flexibility.
Having said that most electricians use the thumb rule of assigning 1.5 A to every outlet. With the 80% safety factor, a 20 A circuit should not carry more than 16 A.
Many professional electricians use the combination of the two and recommend limiting the number of receptacles to just 10 in a 20 amp circuit. I believe it is a good practice to follow.
Other electricians argue that since all receptacles are unlikely to be used simultaneously, you do not need the 80% separate safety factor when it comes to receptacles. They recommend installing 13 receptacles in a 20 amp circuit.
Nothing wrong with this line of thinking except that you can then extend the logic to install even more than 13 receptacles in a 20 amp circuit.
The bottom line is that a 20 amps circuit is enough for a garage, in most cases. You will need to use a dedicated and a higher amp circuit for appliances or power tools that are rated higher than 1920 W. Some examples are:
- Space Heaters
- Window AC
- Table and Miter Saws
A typical garage will have multiple 20 amps circuits emerging from a 60 amp or a 100 amp subpanel.
Thank you very much for reading the post. I do hope you found it informative and useful.