Water and Electricity Costs

Overcome this customer objection with the math

It doesn’t cost much to change the water in a spa. 

When helping people with water care, we often run into situations, such as cloudy water from bather overload and abuse, where the simplest and fastest way to fix the issue is to drain and refill a spa. 

In many instances, the pushback from the client is that water is too expensive and they want to try and save it.

Unless your client is trucking water in, a gallon of municipally supplied water costs right around 1.5 cents with the sewer/discharge fee factored in. This means it will cost $6 to fill a 400-gallon spa — much less than trying to chemically correct hot tub water.

We’ve had people argue when we tell them how inexpensive water is, saying it costs crazy amounts of money to fill their spa — $50, $150 and even $300. By having the client provide their water bill, or by looking up water costs online, we can calculate the cost.

We have looked at water costs around the world, and it always comes down to about 1.5 cents per gallon. The most expensive water we’ve found so far is in San Diego. At the top tier for domestic water, consumers are paying $8.67 per hundred cubic feet, HCF, of fresh water. There are 748 gallons in one hundred cubic feet. If you divide $8.67 by 748 gallons, you get $0.0116 per gallon, or 1.16 cents per gallon for fresh water.

Don’t forget the discharge fee/sewer rate. San Diego charges $5.17 per HCF for sewer, and the volume is based on 95% of your total freshwater use. This works out to $0.0066 per gallon, or 0.66 cents a gallon, for every gallon of fresh water, that San Diego charges for sewer fees.  

Adding the fresh water and sewer charges together, a gallon of water in San Diego costs domestic users at most 1.82 cents. That translates to $7.28 to fill a 400-gallon spa and $36.40 to fill a 2,000-gallon swim spa — a lot less than it will cost to add shock, clarifier, alkalinity and pH adjusters to try to save messy water.

After explaining the real cost of water to clients, they often respond with how expensive it is to heat the freshly filled spa.

Electricity is measured in kilowatt-hours. In the U.S., Hawaii has the highest average electricity rate of 42.69 cents per kilowatt-hour, while Utah has the lowest at 11.22 cents. For this example, we will use the U.S. national average of 16.21 cents per kilowatt-hour.

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To give you an idea of how much electricity is required, a one-horsepower motor running for one hour will use about 1 kilowatt of energy, so a one-horsepower motor uses 

1 kWh of electricity, which means a consumer will spend 16.21 cents to run a one-horsepower motor for one hour.

A 1/5 horsepower hush pump would use 1/5 of a kilowatt in an hour, or 3.2 cents an hour to run. A 5-kilowatt heater (which is about the largest heating element on spas) will cost 5 x 16.21 cents per hour to run, which is 81 cents an hour.

Our 400-gallon spa heats up at the rate of 7 degrees an hour. If the spa was filled with water that was 62 degrees out of the tap and you want to raise the temperature to 104 degrees — an increase of 42 degrees — it will take 6 hours to heat the water. Since the heater uses 81 cents of electricity per hour and has to run for 6 hours, it will use $4.86 of electricity to heat the spa water to 104 degrees.

The average cost of changing 400 gallons of water is the sum of the cost of the water, sewer and electricity, which in this example is $10.86.

While electricity, water and sewer costs vary by region, and while some water out of the tap may be warmer or colder than our example, the next time you have a client struggling where a water change is the best-suited remedy and they are reluctant because of cost, share this article with them, and help them to get back on track to enjoying their spa sooner than later.

Calculation for filling a spa

1.5 cents/gallon (water + sewer)
x 400 gallons (spa capacity)
= $6

Calculation for heating a spa

For a 42-degree increase:
6 hours (7 degrees/hour)
x 81 cents/hour (5-kilowatt heater)
= $4.86

Total cost to drain/refill a spa

$6 (water and sewer)
+ $4.86 (electricity)
= $10.86