Pool Pump Energy Costs

Pool pump horsepower ratings have, for many years, been very confusing and probably will continue to be so until it is standardized. At present time, the only way to compare pump motors is to multiply the horsepower rating (HP) by the service factor rating (SF) on the nameplate of the motor. This gives you the true horse power of the motor, or SFHP.
Examples:
A 1HP motor with an SF of 1.25 will have a true rate of 1.25 SFHP.
A ¾ HP motor with an SF of 1.29 will have a true rate of .95 SFHP.

To figure out how much power (watts) a motor consumes you multiply the voltage (115/230) times the amperage. On the nameplate this might read Maximum load, Max. Amps, or Amps.
Examples:
A 1HP motor at 230 volts times 7.6 amps = 1748 watts
A ¾ HP motor at 115 volts times 13.4 amps = 1541 watts

This is how many watts your motor consumes in one hour. If you divide the watts by 1000 you get Kilowatt hours (kWh). The current cost, no pun intended, of electricity at my place is $.113 per kWh. (Fall 2009) You can check your own costs by adding up the charges for the total kWh used plus the delivery costs and dividing by the kilowatt hours used.
Examples:
1 HP: 1.748 kWh x $.113 x 24 hours x 30 days x 5 months = $711.00
¾ HP: 1.541 kWh x $.113 x 24 hours x 30 days x 5 months = $626.88

The above standard motors are called “Open Drip Proof” and are 60% efficient. That means that 40% of the electricity used is converted to heat. The motor is called open because a fan has to move ambient air through the motor in order to cool it.

If you use a Capacitor start / Capacitor run motor on your pump you will have additional savings. The Sta-Rite Max-E-Pro pump model P6E6C-204L runs on a ½ horsepower motor with an SF of 1.9 (.5 x 1.9 = .95 SFHP) and consumes 1,265 watts. When you compare it with the above ¾ HP rated motor you see that they both have the same SFHP rating; however the capacitor start / capacitor run motor consumes 277 watts less per hour, a savings of $112.64 over a 5 month season. This is also a new generation pump with higher pumping capacities. The difference in price will be paid for within 2 years. Cap start/Cap run motors are 65% efficient.

Over the last 2 years we have seen the development of High Performance Pumps. Sta-Rite IntelliPro VS 3050 has a 6 pole permanent magnet motor with 4 programmable and adjustable speeds. This motor is 95% efficient and is totally enclosed. What little heat remains is dissipated by an external fan.

One speed might be used to maintain the water circulation in your pool at an optimum 2.5 time turnover in 24 hours. This is the standard turnover rate for residential pools. Another speed might be for pool vacuuming. Others can be used to run an overflow spa or a waterfall. You save money by using only one pump for different purposes, and you can fine tune it to use a minimum amount of power to filter your pool. This motor can also be controlled directly by pool automation systems, which can turn the speed down during peak electrical time-of-use periods. If you are an electronics fan, you can even arrange to control the automation system and the pump over the internet. These pumps will likely become more common and more affordable over the next few years. The state of California has mandated that any motor over 1HP be either 2 speed or permanent magnet on all new pool installations.