Yes, A Variable-Speed Pump Really Saves You Money

It isn’t some big secret that owning a pool is expensive, so owners have been looking at ways to save for years.

The moment your electric bill arrives each month in particular can make you wonder if you are powering a small city instead of your pool.

The primary culprit is usually your pool pump. Traditionally, these have been single-speed machines. But a shift in technology has brought variable-speed pumps (VSPs) to the forefront.

It’s a bigger cost upfront, but you could see savings in as little as 2-3 years, especially with the rising costs of electricity.

Why Variable-Speed Pumps Will Eventually Save You Money

It isn’t just about better parts, but rather a fundamental shift in how water moves through your pool system.

Here is the breakdown of why VSPs are essentially long-term money-saving machines.

Pure Energy Efficiency

The standard single-speed pumps are induction motors and only run on one speed, usually 3,450 RPMs. You are either full blast, or off.

Dual-motors are a little better, but they only run on two speeds.

VSPs use Permanent Magnet Motors (PPMs), the same technology found in electric vehicles. This allows much greater flexibility in terms of RPMs and power used. While induction motors might be around 30 – 70% efficient depending on the model, a PPM motor can reach upwards of 90%.

Just by the motor itself, VSPs are much more energy efficient.

The Pump Affinity Law

The makeup of the pump is one thing. The true money-saving power of VSPs is due to the Pump Affinity Law. This states that the power consumed by a pump is proportional to the cube of the shaft speed.

In most areas of life, if you do half the work, you use half the energy. But water doesn’t work that way. Because of how water moves, there is a massive “bonus” for slowing down. The reduction isn’t linear.

In super simple terms, this is called the 1/8 rule. If you cut the pump’s speed in half, the power consumed doesn’t just drop by half. It drops to 1/8 of the original power.

When you change the speed of your pool pump, three things happen at very different rates:

• Flow is Proportional: If you cut the speed by 50%, you get 50% of the water flow. This is a 1-to-1 relationship.
• Pressure is Squared: If you cut the speed by 50%, the pressure (head) drops to 25% (0.5 x 0.5). This makes it much easier on your pipes and filter
• Power is Cubed: If you cut the speed by 50%, the power consumption drops to 12.5% (0.5 x 0.5 x 0.5). Or, 1/8!

By simply slowing down the motor to half-speed, you aren’t just saving 50% of power consumption. It’s actually 87.5%!

Let’s See a Real-World Example

Let’s look at a scenario to see the cost-savings in action. Assume your pool holds 20,000 gallons and the local electricity rate is $0.16 per kilowatt-hour (kWh).

A standard single-speed pump is 1.5 HP and has a flow rate of 66 gallons per minute (GPM). We want the pool’s water to “turnover”, or run through the entire system once per day.

Using this math, you’d need to run the pump for at least 5 hours a day:

(20,000 gallons / 66 gpm) / 60 min = 5.05 hours

These pumps also consume an average of 2,000 watts per hour. With this, we are looking at 10,000 watts, or 10 kWh per day:

(2,000 watts * 5 hours) / 1,000 = 10 kWh

The daily cost of running your pool is $1.60 per day (10 kWh * $.16).

Let’s swap that single-speed with a VSP. Instead of full speed, the VSP will run at half speed. This drops our GPM to 33 and increases our pump time to 10 hours for a full turnover.

But here is the savings at play. Because of the Pump Affinity Law, we are only drawing 250 watts instead of the 2,000 of the single-speed pump.

With the VSP, we will consume 2.5 kWh per day. That is a daily cost of $0.40!

When you break it down, that’s a savings of $36 per month, or $432 per year!

Get your own estimates by using our pool pump savings calculator.

Make the Switch

Yes, VSPs are more expensive upfront for the actual pump and installation. However, based on your individual factors above, you could be seeing a payback in as little as 2-3 years!

Finding the right pump might be tricky, but it will be worth it in the end.