Variable Speed Pump Lowers Energy Costs

Riverview Pool and Electrical Contractors Serving Tampa

Often in homes with a pool, the pool is the greatest household energy consumption. To lower costs, consider installing a variable speed pump in place of your old single speed pump. It can reduce energy expenditures 50 to 90 percent, where a single speed pump runs constantly from 5 to 24 hours per day, wasting energy and your money.

Single Speed Pumps: The Old Standby Meets Its Match With the Variable Speed Pump

Because it runs continuously and has no flow rate adjustment, the single speed pump constantly consumes energy. That energy consumption means higher energy bills. The problem is that a single speed pump with its 1 to 2 horsepower motor runs ceaselessly with no reduction in revolutions per minute (rpm).

Conversely, the variable speed pump can make flow rate adjustments by reducing rpm, meaning a higher or reduced flow rate when necessary. The result is a reduction in energy usage and costs. This “intelligent” system provides greater long-term cost savings due to less water and power usage.

Calculating Variable Speed Pump Savings With the Pump Affinity Law

When you install a variable speed pump, you reduce motor speed and flow rate, resulting in reduced energy consumption. The Pump Affinity Law explains how the variable speed pump saves energy:

Speed = rpm (rotations per minute)
Flow = gpm (gallons per minute)
Power = W (watts)

The average single speed pump has a fixed flow rate of 3,450 rpm, while the average pool holds 25,000 gallons of water with an average turnover rate of 24 hours.

Let’s assume that a single speed pump takes 2,000 watts, operates at 3,450 rpm, and has a flow rate of 66 fpm:

(25,000 gallons / 66 gpm) / 60 minutes = 6.3 hours.

The single speed pump can turn over the entire pool in 6.3 hours at this rate, which would consume 12,600-watt-hours per day:

6.4 hours x 2,000 watts = 12,600 watt-hours (12.6 kWh)

A variable speed pump can operate with a flow rate of 22 gpm while only taking 116 watts. It may take longer to turn over the pool’s water, but it saves energy and money:

(25,000 gallons / 22 gpm) / 60 minutes = 19 hours

19 hours x 116 watts = 2,200 watt hours, or 2.2 kWh consumed per day.

Source: https://www.nrel.gov/docs/fy12osti/54242.pdf