Demand Controlled and Energy Saving Pumps

Two authors discuss how these water pumps save money by working only as hard as they need to

August 20, 2015
September/October 2015
A version of this article appears in the September/October 2015 issue of Home Energy Magazine.
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Save Money with Energy Star-Certified Pool Pumps

A pool pump could be an energy waster second only to a home’s heating and cooling system, costing a homeowner over $450 annually. Save energy and money for your clients by replacing single-speed pool pumps with Energy Star certified pumps. Save how much money? See Figure 1.

How Does an Energy Star Pool Pump Save Energy?

Pool pumps circulate water through filters and power cleaning systems. Filtration, which is what pool pumps are mostly used for, requires half the flow rate of pool vacuuming. Conventional single-speed pool pumps use the same pump speed regardless of the task being performed. An Energy Star-certified pool pump can change speeds, saving enormous amounts of energy. With the ability to run at the lower speeds needed for filtering, an Energy Star-certified pool pump

  • uses up to 70% less energy than standard pool pumps;
  • saves up to $340 per year and over $2,000 over its lifetime in reduced electric bills; and
  • can pay for its additional upfront cost in less than two years.
Annual Energy Costs for Pool Pumps

Annual Energy Costs for Pool Pumps
Figure 1. An Energy Star pool pump will save you $280-$340 per year and over $2,000 over its lifetime in reduced electric bills. (EPA)

Table 1. Efficient Pool Pump Incentives

Table 1. Efficient Pool Pump Incentives

Energy Star pool pumps also run more quietly and prolong the life of a pool’s filtering system. (EPA)

Signs a Pool Pump Needs to Be Replaced

The most obvious sign a pool pump needs to be replaced is that the motor is completely dead. However, there are other signs. Recommend that your clients replace a pump that

  • is seven to ten years old;
  • seems less powerful than it was;
  • makes noise continually;
  • gets hot and shuts down;
  • hums or buzzes but will not start; or
  • starts slowly.

However, with such a huge potential for savings, this is an upgrade that makes sense even when the current pump is still working.

Utility Incentives Available

To sweeten the deal, many utilities offer incentives of up to $300 per pump (see Table 1). Check with your local utility to learn what incentives it may offer to your clients.

Energy Star Pool Pump Calculator

EPA has created a savings calculator to make it easy for energy professionals, pool professionals, and homeowners to see the benefits of an Energy Star-certified pool pump. To calculate savings, users can adjust

  • location;
  • electric rate;
  • months per year of pool operation;
  • pool size in gallons (which can be determined with the included pool size estimator);
  • size and operation of conventional pump; and
  • Energy Star pump being considered.

If any of these inputs is not known, the calculator defaults to values vetted by industry experts.

Think about including a pool pump in your next energy audit. You could save money for your client and create some positive word of mouth for your company.

—Steve Ryan

Steve Ryan is the EPA Energy Star Program Manager.


The Long-Bullet Effect

How many times have you turned on a hot-water faucet and waited what seemed an eternity for the water to get hot? You may remember that the water first became noticeably warm before it finally got hot—sometimes trying your patience. The process of going from warm to hot is often referred to as the long-bullet effect.

In 2007, Koeller & Company published a report of best water efficiency practices in buildings. One chapter dealt with residential hot-water distribution. In this chapter, the concept of the long-bullet effect was presented in a figure that showed water flowing in a plumbing system, going from cold (ambient) to warm and finally to hot (see Figure 1).

The Long-Bullet Effect

The Long-Bullet Effect
Figure 1. The long-bullet effect refers to the time it takes for warm water to get hot in a residential plumbing system. (EPA)

Untitled
This Sierra Vista, Arizona, subdivision's homes all use pump plumbing technology that helps negate the long-bullet effect, which reduces wasted water, energy costs, and time. (Dave Grieshop)

Wasted Water—Cold to Hot and Warm to Hot (Reality LLC)

Wasted Water—Cold to Hot and Warm to Hot (Reality LLC)
Figure 2. This graph shows 73 sets of data from kitchen and master bathroom hot-water fixtures. It shows how much water homeowners waste per year as they wait for their water to get hot. (EPA)

Annual Wasted Gallons of Water

Annual Wasted Gallons of Water
Figure 3. The amount of water homeowners waste per year as they wait for their water to get hot is shown here in ascending order based on cold to hot gallons. (EPA)

I've been examining this effect by working with homeowners all over the United States who have collected the behavioral data from their own homes. These homeowners understand that the water wasted while waiting for hot water was hot once before. They understand that waiting for this water to get hot again means wasted energy and money. In addition, the water itself is wasted, since it goes down the drain. (For the purposes of this article, all wasted water is considered “down the drain,” although it is true that some homeowners collect it and use it.)

Note that any insights into data collected on the long-bullet effect are fraught with errors. For example, given the same hot-water fixture, it might take a few seconds longer for the water to begin to get warm first thing on a winter morning than at midafternoon on a summer day.

So why collect data on the long-bullet effect in the first place? Simple. As far as I am aware, based on comments from experts in the plumbing field, behavioral data on the long-bullet effect have never been collected from homeowners before. While the data may not be precise, they are worthwhile. With that in mind, let’s look at 73 sets of such data.

The Data

Waiting for hot water has two components. These are

  1. total elapsed time until the water is hot (where hot is defined as hot enough to shower); and
  2. the time between the moment when the water first begins to feel warm until the moment when the water is hot. Warm-to-hot elapsed time is the long-bullet effect.

Figure 2 shows the total number of gallons of water wasted per year for the 73 sets of data. That is, it shows the gallons wasted going from cold (ambient) to hot, and the gallons wasted going from warm to hot. These findings assume four daily demands for hot water, three at the kitchen sink and one in the master bathroom.

Figure 2 doesn’t reveal any special insights. It shows only that the data points are all over the place. The database on which the graph is based shows that the total elapsed time spent waiting for hot water ranged from 7 seconds to 195 seconds, and the time spent waiting from warm water to hot water ranged from 4 seconds to 94 seconds. That said, the average time spent waiting for hot water was 59 seconds. No wonder some homeowners do something else while waiting for hot water!

When these same paired data are placed in ascending order of annual gallons wasted while going from cold to hot, insights emerge.

Figure 3 shows that 1,750 gallons of water are wasted going from cold to hot, and 500 gallons of water are wasted going from warm to hot. These 500 gallons represent 29% of the total waste. Said another way, of every 4 gallons of water wasted while waiting for hot water, a little over 1 gallon is wasted due to the long-bullet effect. If the average time spent waiting for hot water is 59 seconds, this means that 17 of those seconds are spent waiting for the water to go from warm to hot. That is adding insult to injury.

Think about this: The waste attributable to the long-bullet effect occurs in tens of millions of homes every day. Any manufacturing business with such a percentage of waste would go broke in short order.

There has to be a better way—and there is.

When it comes to existing homes, installing demand-controlled pump technology has a profound effect on the entire plumbing system. Water and time waste reductions with a factor of 5 to 6 have been demonstrated when pump technology is installed in these homes. This was addressed in my article in HE online Mar/Apr ’15, “Hot Water: Why Plumbing Technologies and System Designs Matter.”

learn more

See a full list of Energy Star certified pool pumps—hundreds of models made by all the major pool pump manufacturers.

The EPA pool pump savings calculator is available as an Excel file to download.

Have more questions? Check out energystar.gov/poolpumps and start saving today!

What’s Next

I am currently studying ten new homes that meet the current EPA WaterSense hot-water delivery standard of 0.6 gallons. There are at least four design approaches that can deliver these results in new residential construction. The opportunity is now for municipalities and water agencies to consider adopting this EPA standard, and to permit the building trades to choose their solution. There is a better way, especially as the Southwest confronts diminishing water supplies during the ongoing prolonged drought.

—Dave Grieshop

Dave Grieshop is managing partner of Reality LLC, in Sierra Vista, Arizona.

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