Pool Pump Horsepower vs Watts: How to Compare

What horsepower and watts mean in a pump listing

A pool pump listing states horsepower (HP) and sometimes wattage (W). These two figures measure different things. Horsepower is a unit of mechanical power, describing the motor's output capability. Watts measure electrical power, the rate at which the motor consumes electricity from your home's supply.

The relationship is fixed by physics: 1 horsepower equals 746 watts. So a 1 HP motor produces 746 watts of mechanical power. But the electrical power it draws from the wall is higher, because motors are not 100% efficient. Some energy is lost as heat. The wattage stated on a pump listing is usually the electrical input, which is what your energy bill reflects.

When you see a pump titled "1.5 HP" and another "1,100 W," you are looking at two different numbers. The HP figure tells you the motor's output potential. The wattage tells you how much electricity it consumes. To compare energy use, focus on the wattage, not the HP.

For a deeper look at how horsepower is stated on listings, see how to read horsepower on a pool pump.

How to convert horsepower to watts

To convert horsepower to watts, multiply the HP figure by 746. For example, a 1 HP pump produces 746 watts of mechanical power. A 2 HP pump produces 1,492 watts. This conversion gives the motor's output, not its electrical draw.

The electrical draw is always higher. A typical pump might draw 1,200 to 1,500 watts for a 1 HP motor, depending on efficiency. The difference between the mechanical output and the electrical input is the motor's efficiency loss, which appears as heat.

When a listing states wattage, use that number directly for comparing energy use. When a listing only states HP, you can estimate the electrical draw by multiplying the HP by a factor, but the exact figure depends on the motor's efficiency, which the listing may not state. For a precise comparison, look for the wattage or the motor's efficiency rating.

The site does not convert units or calculate energy use for you. The conversion above is a general explanation of the units. For your specific pump, use the maker's specifications and the wattage stated on the nameplate.

Why wattage matters for energy use

Your electricity bill is based on kilowatt-hours (kWh), which is the product of power in kilowatts and time in hours. A pump that draws 1,500 watts (1.5 kW) running for 10 hours uses 15 kWh. A pump that draws 750 watts (0.75 kW) running for the same time uses 7.5 kWh. The lower wattage pump uses half the energy.

This is why variable speed pumps are often recommended. They can run at lower speeds, which reduces the wattage draw. The ENERGY STAR program explains that reducing pump speed by one-half allows the pump to use just one-eighth as much energy. This is a general principle, not a claim about any specific pump.

When comparing two pumps, the one with lower stated wattage will generally use less electricity at the same run time. But the actual energy use depends on how you operate the pump, including the speed setting and run hours. A higher HP pump running at full speed will use more energy than a lower HP pump running at a lower speed.

For more on how speed affects energy use, see variable speed vs single speed.

How to compare pumps in listings

When you look at pump listings, you will see horsepower, voltage, and sometimes wattage or amperage. To compare energy use, follow these steps:

First, note the horsepower. This tells you the motor's size and output capability. Second, look for the wattage or amperage. If the listing states watts, use that number. If it states amps, you can multiply amps by voltage to get watts (for example, 10 amps at 115 volts is 1,150 watts). Third, consider the speed type. A variable speed pump can run at lower wattage than a single speed pump of the same HP.

The site does not size pumps or calculate energy costs. The comparison above is about reading the listing terms. For your pool, use the maker's sizing page and consult an installer.

For a checklist of what to look for, see how to read a pool pump listing.

• Horsepower: the motor's output, not its energy use.
• Wattage: the electrical power draw, which affects your bill.
• Amperage: multiply by voltage to get wattage.
• Speed type: variable speed pumps can run at lower wattage.

What this site cannot say about energy use

This site does not provide energy savings figures, cost per month, or payback periods. Those depend on your local electricity rates, run time, and pump operation, which are not stated in listings. The site also does not calculate the correct pump size for your pool. That requires knowing your pool's volume, plumbing, and flow requirements, which are beyond the listing details.

For energy efficiency information, the ENERGY STAR program explains that certified pool pumps can save energy, but the site does not repeat specific savings claims. You can read the ENERGY STAR pool pump page for general information about the program.

For questions about wiring or electrical requirements, a licensed electrician and the maker's manual decide that. The local building office can answer code questions.

The site's buying guides compare pumps based on stated details, not on measured performance. See the best variable speed pool pumps guide for a starting point.

What to pick for your situation

Questions

How many watts is a 1 HP pool pump?

A 1 HP motor produces 746 watts of mechanical power. The electrical draw is higher, typically around 1,200 to 1,500 watts, depending on efficiency. Check the pump's nameplate for the exact wattage.

Is higher wattage always worse?

Not necessarily. Higher wattage means more energy use at the same run time, but a higher wattage pump may be needed for high flow applications. Compare wattage only between pumps that meet your flow needs.

Can you convert watts back to horsepower?

Yes, divide watts by 746 to get mechanical horsepower. But this is the output, not the electrical input. The electrical input is what you pay for.

Why do some listings not state wattage?

Some sellers only state horsepower. You can estimate wattage by multiplying amps by voltage, but the exact figure depends on the motor's efficiency. Contact the maker for specifications.

Does a variable speed pump use less wattage?

Variable speed pumps can run at lower speeds, which reduces wattage draw. The ENERGY STAR program notes that reducing speed by half uses one-eighth the energy, but actual wattage depends on the speed setting.