Like many other motors, garage door openers are rated with horsepower (hp) or horsepower similar (hps) for DC motors. Based on this rating a 1/2 HP opener should be able to lift about 185 pounds and a 3/4 HP opener should be able to lift over 370 pounds. Unfortunately, this is not the case since those ratings are based on maximum output and fail to take into account built in safeguards on newer units. Manufacturers have added excessive force auto shutoff and a nylon gears that fail when too much force is exerted.
Actual figures are closer to 125 lbs for a 1/2 HP and 175 lbs for a 3/4 HP. These numbers will be difficult to calculate precisely since variables like date of production and age are hard to account for. Newer openers won’t be even close to these numbers due to the multiple safeguards to be discussed below.
Residential garage door openers were never designed to lift the full dead weight of your door although they probably could – for a short period of time. Instead openers were created to lift a little weight over a long period of time in order to assist your torsion or extension springs in operating the door . On a balanced door system where the springs counterbalance the total door weight, openers only have to exert 15-25 pounds of force. In other words, springs counterbalance 90%-95% of the total door weight.
Table of Contents
What is garage door opener horsepower?
The mathematical definition of (1) Horsepower is 33,000 pounds, one foot high, in one minutes time. Breaking that down to seconds we can simply divide by 60 (60 seconds in 1 minute). The simplified definition becomes (33,000/60) 550 pounds, one foot high, in 1 second – much easier to work with.
Another problem is openers don’t lift the door 1 foot per second. According to Chamberlain Liftmaster most residential openers lift the door an average of 8 inches per second. That means we have to divide our answer by 2/3 (0.67)
Residential garage door openers have horsepower ratings of 1/3 HP, 1/2 HP, 3/4HP, 1 HP and 1 1/4 HP (Commercial openers go much higher). To find the weight each opener can lift simply divide 550 lbs by the manufacturer HP rating and then multiply by (2/3).
For example, a 1/2 horsepower garage door opener should be able to lift 275 pounds while a 1 HP opener can lift 550 pounds.
550 * 1 HP * 2/3 = 369 pounds
550 pounds * 1/2 HP * 2/3 = 184 pounds
The above back of a napkin math may not be 100% correct and is certainly open for correction, but real world experience backs up those figures. Often times homeowners would have broken springs and continue running their openers without realizing it. After a while the openers would fail from lifting the dead weight of the door without spring assistance. Many of these doors were 125-200 pounds.
Opener Parts Fail From Excessive Force
That sounds like a lot of power- but not so fast! Garage door opener manufacturers have recognized that this type of lifting capability could be a safety liability as well. Can you imagine if a shovel or something tragic like a childs arm getting stuck in the door tracks? These horsepower (HP) ratings also represent peak hp and are not sustainable for any length of time – its a great marketing tactic though. Thankfully, 3 main fail-safes were created to prevent serious damage to person and property otherwise your door, opener and body could be seriously injured.
- Safety Auto Reverse Feature
- Automatic Excess Force Shutoff
- Nylon Gear & Sprocket Assembly
Safety Reverse Feature
Newer openers are equipped with auto reverse and excessive force detection features. If something obstructs the door from opening or closing during its pre-programmed travel the safety reverse feature will activate. If the door thinks something is in the way it will reverse and go back up. If you have purchase a home with an older garage door opener be sure to test this safety feature to make sure it is still working.
- Safety Reverse Test: Open your garage door and put a 2×4 on edge in the path of the door opening. Press your remote, keypad or wall control to close the door. It should hit the wood board and reverse back up. If it doesn’t you will need to have the opener serviced or replaced.
Excessive Force Shutoff
If the door should close on a person or object and fail to stop and reverse, an excessive force shutoff would trigger (newer openers). Not only does this prevent accidents, but it also alerts the homeowner that the opener is overworking itself. That is often the case where one or both torsion springs break without the homeowner noticing. If your garage door shoots off excessive force light flash codes check to make sure your springs aren’t broken.
Nylon Gear Stripped Out
The last fail safe is the plastic gear inside the motor casing. The teeth on the gear will strip out if all else fails. Chances are you may have already had to have this part replaced if you have an older opener. Turning up the force on your opener to compensate for an unbalanced door is the fastest way to destroy the nylon gear inside. On a screw drive opener system produced by Liftmaster and Genie the carriage assembly is the part that will fail instead of the nylon gear.
How much horsepower do I need?
Torsion and extension springs do most of the heavy lifting while openers are designed to move the door – as in getting the process started. Unbalanced doors will destroy the lifespan of the garage door opener, regardless of what horsepower you purchase. Nylon gears, limit switches and the top section of your garage door will be stressed too far and fail prematurely.
Contrary to popular belief 1/2 openers will work on most standard residential steel garage doors. Again, the torsion springs should counterbalance 90-95% of the total weight of the door. So even if your garage door weighs 250 pounds the opener would only be lifting between 10-25 lbs. If that is not the case it is likely the springs that need adjustment or replacement.
Do garage doors freeze to the ground?
Extra horsepower might be necessary in some circumstances even with a balanced door. If you happen to live in a climate with extremely cold winters, snow and ice buildup can be a problem. The bottom seal of the door can freeze to the ground and the joints where the sections come together can ice over. This creates a situation where the door may require double or triple the necessary lifting force to operate, causing parts to fail. This is very common and that is why the garage door service business is seasonal – winter being much busier than the warm summer months.
If your garage door freezes to the floor its best to try to pry it free without running the opener. Rock salt and other de-icing agents can also be used where the bottom section hits the ground.
Door Sticking When the Opener Starts
In summer months some homeowners experience the garage door sticking. This is usually caused when the door is installed in winter, with the perimeter vinyl door seal contracting from the cold. Then in hot summer months temperatures hit 90-100 degrees and the seal swells as the door absorbs heat.
This expansion presses the seal firmly against edges of the face of the door giving the door a sticking sound. Most people perceive this as the bottom seal sticking to the ground, when its actually the side seals. The added force of the seal installed too tight to the door face adds significant weight.
A few things can fix VDS installed too tight against the door. First, raise the door to the open position and look for areas on the VDS that have turned black from friction. Those are the areas you can try to sand down with sandpaper. You can also put a piece of wood against those areas and lightly hit the board with a hammer. A few millimeters or extra space can be enough to eliminate sticking.
|Maximum Door Weight||Horsepower Rating||Chamberlain Model||Liftmaster Model|
|0-125 lbs||1/3 HP||C203 - Chain||8010 - Chain|
|0-300 lbs||1/2 HP||C410 - Chain|
C450 - Chain
B510 - Belt
|8365W - Chain|
8355W - Belt
|0-500 lbs||3/4 HP||B750 - Belt||8587W - Chain|
8550W - Belt
|0-650 lbs||1 HP***||RJO20 - Jackshaft|
C870 - Chain
B970 - Belt
|8500W - Jackshaft|
Chamberlain Liftmaster doesn’t produce a 1/3 HP opener any more. Last production was the Liftmaster 1345 & 3110. Above openers are contractor grade.
DC motors aren’t rated with horsepower, but for the purposes of comparison they are given a horsepower equivalent.
Above ratings assume a balanced and maintenance door and average usage.
HPS (Horse Power Similar) is a designation indicating the high-quality DC motor in this garage door opener features pulling force similar to an AC motor. This designation is provided for comparison purposes since DC motors are not typically measured in horsepower. -Chamberlain Liftmaster
How long do garage door openers last?
Opener lifespan depends on a lot of factors including usage, door balance, climate and horsepower. Openers can last 15-20 years, but several of the components inside will fail much earlier than that.
In my early years in the door business as a showroom salesman I sold a lot of nylon gears – especially in the winter months where doors would freeze to the ground. Selling a dozen or more in one week to walk in customers wasn’t unusual from November through February. Our service technician in the field probably doubled that figure.
The thing about garage door openers is that the motor itself almost never blows up. That is why a lifetime motor warranty is provided with most Chamberlain Liftmaster opener purchases. The manufacturers know that the user will never cash in on that warranty. The same can be said for a “lifetime” belt warranty. The belt assemblies are reinforced with steel threads inside, making them hard to stretch and extremely durable.
Gears, logic boards and limit switches were three of the main parts that needed frequent replacement. In my 8 years selling openers wholesale, I never once encountered a motor that burned up. The owner of the business I worked for only saw one occurrence of a motor going bad in over 30 years at the place.
Common Opener Parts Lifespan
|Opener Part||Lifespan||Cost||Repair Time|
|Nylon Gear||8-12 years||$15||45 minutes|
|Gear & Sprocket||8-12 years||$30||30 minutes|
|Limit Switch||10-12 years||$15||30 minutes|
|Logic Board||12-15 years||$60-$100||45 minutes|
|Belt Assembly||Lifetime||$70||50 minutes|
|Chain Assembly||Lifetime||$70||50 minutes|
Motors, chains and belts rarely break – that’s why they are often sold with a lifetime warranty.
When I sold commercial duty operators it was always based on the square footage of the door it was being installed on. Other options like track configuration were also a factor. Square footage isn’t necessary that important, but it has a direct correlation with total door weight. The manufacturers provided charts to all the salesman so we could provide the minimum opener requirement. These charts didn’t exist for residential openers because all of them would work just fine on a properly installed and maintenance door.
Can I use my opener if the door has a broken spring?
Most garage doors have a pair of springs installed rather than one single spring, although single car doors may have only one. In the event your springs break you can use your opener for emergency purposes only. You can pull the red emergency release cord and attempt to dead lift the door off the ground manually, but you may need 2-3 people to help you.
Running the opener frequently with a broken or unbalanced spring will strip your nylon gear inside the opener casing and could also cause damage to the top section of your door. The center stile at the top of your garage door may not be able to handle the full force of the J arm pulling against it. This leads to the center stile literally ripping off the top section.
A garage door reinforcement bracket should always be used instead of the attachment clip that comes standard in the opener installation box.
Testing the Lifting Force
- Put the garage door in the closed position and then unplug the power cord. If your opener is hardwired you will need to turn off the circuit in the electrical box.
- Pull the red emergency release cord to disconnect the openers J arm from the top door section.
- At this point you have 2 options: Holding on to the bathroom scale, lift until the door starts moving up and record the weight. The other option is to set the door down on top of the scale and record the weight reading.
- If your scale reading is more than 15 pounds for a single car door or 25 pounds for a double car door your torsion springs need adjustment.
- Garage door openers are capable of lifting heavy door weights for a short period of time, but are intended to move a little weight over a long period of time.
- Several fail-safe mechanisms in the opener drastically cap the advertised horsepower and lift capacity.
- Operators with higher horsepower are a great marketing tool, but only mask underlying door issues caused by improper installation and poor maintenance.
- A 1/2 hp opener is capable of operating most residential doors given annual maintenance and adjustment.
- Perform a balance test and lifting force test to make sure your torsion springs are counterbalancing at least 90% of the door weight. If your opener is lifting >25 lbs its time to service and adjust the door.