Is a 1.0HP Motor the Same as a 1.5HP Motor?

Are All Motors Created Equal?

If you are one of the lucky ones who can still read your motor label, you’re already one step ahead of the game. Searching for your replacement pool motor can seem rather daunting at first. Take your model number, type it into the search field on our site, and VOILA your motor pops up. However, after clicking on the motor you notice one major difference – the horsepower. You are absolutely certain the motor in your hand has a 1.5 horsepower motor, but the one listed on the website is a 1.0 horsepower. Thinking you must have typed in the wrong number, you re-enter the model number again. Same result.

So, is the 1.0 horsepower the same as a 1.5 horsepower?


Because this is a loaded question, we first must understand the dynamics between the specs on your motor label.

First thing first…

ust1152Before we are able to conclude whether the 1.5 horsepower is the same as the 1.0 horsepower, you must first analyze the other specs on your motor.

The essential piece of information you need to look for is called the Service Factor (SF). Sometimes the manufacturer does not lay out this information clearly, so you may need to search for it. The SF measures the overload capacity built in a motor.

You don’t necessarily need to know what the SF means to the operation of the motor, as much as what it actually does. The SF serves as a multiplier to your horsepower which indicates the amount of additional load your motor can handle.

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Calculating Your Total Horsepower

By keeping in mind what the service factor does, you realize the horsepower listed on the label is not the actual horsepower of your motor. To calculate your total horsepower, multiply your horsepower by your service factor. That number will give you your total or true horsepower.


Full rated vs. Uprated

Capture2The differences between a full rated motor and an uprated motor is the gray area which a lot of pool owners have questions about. In short, an uprated motor is taking a smaller horsepower and changing the rating on the service factor to create the impression that the motor has more power than it actually does.

For example, on a 1.0 horsepower full rated motor, the service factor is 1.65, making it’s total horsepower 1.65. But, on a 1.0 horsepower up rated motor, the service factor is only 1.13, making the total horsepower 1.13. This is actually equivalent to a .75 horsepower full rated motor. The chart above shows the typical service factor rating for each horsepower in both full and uprated motors.

Therefore, a 1.0 horsepower full rated and a 1.0 horsepower up rated motor are not the same. You cannot replace a 1.0 full rated motor with a 1.0 uprated motor.

However, you can replace your 1.0 Full rated motor with a 1.5 HP uprated motor. This is because they both will have the same total horsepower.

Don’t fret if your motor is not labeled uprated or full rated. In many cases, it may not be labeled at all. What really matters is whether your total horsepowers are equivalent. Always check your service factor and horsepower to figure out the total horsepower.

Is a 1.0 horsepower motor the same as a 1.5 horsepower motor? Maybe and sometimes. The answer all depends upon the all-important service factor number. The sure way to determine is to calculate the total horsepower by multiplying your horsepower by your service factor and to compare.

The most important thing to remember when replacing a motor is that the replacement motor’s horsepower times its service factor must be equal to or greater than the original motor’s horsepower times its service factor.

If you are ever stuck or cannot find the exact model or part number to your motor, don’t hesitate to give us a call at 877-372-6038 and we’d be more than happy to help find the correct motor.

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15 thoughts on “Is a 1.0HP Motor the Same as a 1.5HP Motor?

    1. i have an ec50ac filter with a 1.5 hp motor . ran well for years. motor rotted out. got a used 1hp motor for it. runs for 20 minutes at full and then pressure guage goes up 5-7 lbs. have to bump it to get good flow. soaked the fingers overnite put bacckk together ran for 1/2 hour pressure went up the 1hp too weak ?

      1. Yes, the weak motor is the exact issue. The 1.5HP pump has a 1.5HP impeller, and the motor has to be strong enough to turn under load. If you put a 1.5HP impeller on a 1HP motor, it will overwork and burn out the pump. So, in short, get a 1.5HP motor or downsize the impeller to 1HP.

  1. I just installed a new 2 HP Motor with the exact same 1.1 SF on the label as the 10 year old bad one and both are Century USQ 1202’s, same impeller, etc. With a new filter and no obstructions anywhere my gauge is reading over 30 psi and it was always around 24 with the old motor. Is it true that these newer motors are more powerful and I should step down to a 1.5 HP now? This high pressure cannot be good?

    1. Flowrate is limited by the impeller. For example, if you take a 2 HP impeller but install it on a 5 HP motor, the impeller will still only be able to produce 2 HP worth of flow. You may want to try cleaning your filter and checking for any obstructions on the pressure-side of the system (from the pump to the returns.)

  2. So I have a A.O. Smith/Hayward motor that has a HP Rating of 2.5 SPL and the service factor is SPL.

    So what do I really have? The Motor is an SP1524-Z-1-EFTC or Part number 7-193812-01. I have a 30 foot round above ground pool that has a 54″ wall. 23,000 to 24,000 gallons of water in the pool. What motor should I be looking for if I need to replace my motor (which I have in pieces on my workbench at the moment?

        1. What type of “domestic purpose” are we talking about? Also, in the article, I try to explain the ways you can figure out if a motor compatible with your original overrated motor.

      1. Can I safely replace my Century pool pump ,1 HP – SF 1& tho 1 with Pentair starite e max pro 1.5 HP & SF 1.65? Thank you in advance.
        Best regards,
        Aybars Ocal

        1. Century is the maker of your pool pump motor, it would identify the pump housing. What is the make and model of your current pump’s housing? I can get a sense of the flowrate once I know that info

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