Payback Period for Low Flow Toilets: Is the Cost Offset by the Water Savings?

How Much Water Do Toilets Use?

The current federal standard for toilets in the U.S. is 1.6 gallons per flush (gpf), but many old toilets use much more water. Older models typically use 3-5 gpf, or even up to 6 gallons.

If you have an old toilet, there are some low-cost options for improving your toilet's water efficiency. For example, you can literally fill a plastic bottle with pebbles or sand and place it in your toilet's water tank (away from the plumbing equipment). This will displace some of the water used for the flush. You can alternatively buy a "tank bank" or other water-saving device, which serve the same purpose. These usually only cost a few dollars.

However, if you are looking to replace your toilet, it's best to look for a low flow toilet. A low flow toilet is simply a toilet that uses less water per flush than an average toilet. While they may cost more money up front, they will save you money in water bills over time.

What to Look for in a Low Flow Toilet

When looking for a new toilet, it's best to shop for a WaterSense labeled model. WaterSense is the U.S. Environmental Protection Agency's program for labeling water efficient, high quality appliances and products, which helps consumers make smarter purchasing decisions.

WaterSense labeled models use 20% less water than average toilets and are tested by a third party organization for quality and performance. This ensures that while the toilet uses less water to flush, the flush is still powerful and effective. The EPA estimates that labeled models will save a family of four $90 per year and $2000 over the life of the toilet.

Cost, Payback Period and ROI

The costs for water efficient toilets widely varies based on model, manufacturer, and other features. According to CostHelper, an basic toilets cost $100-325 or an average of $176 (without installation).

Popular toilet manufacturers include Kohler, TOTO and American Standard, and all three have low flow models available. In fact, TOTO owns nearly a third of the market share for toilets. Therefore, to calculate a potential cost savings, we'll compare a TOTO low flow and conventional (1.6 gpf) toilet. Keep in mind that as a premier toilet brand, their prices skew higher, but comparing two toilets of the same brand will help with our price comparison.

We will assume for our example that the home has an older toilet with 4 gpf. For the conventional 1.6 gpf example, we will use TOTO's basic Carusoe, which retails for $227 on the company's website. We will compare this to TOTO's low flow Eco Drake toilet, which has a flow rate of 1.28 gpf, is WaterSense labeled, and retails for $364.

The EPA says that the average price of water is $2.00 per 1,000 gallons. We will estimate that each toilet is used by a family of four. The average person flushes a toilet 2000 times per year (about 5-5.5 times per day). Let's assume half of these flushes take place at home, meaning that four people flush the toilet 4000 times a year in the house.

Payback Period:

The old toilet at 4 gallons per flush, if flushed 4000 times in one year, will use 16,000 gallons. At $2/gallon, this will cost approximately $32.00 per year.

The conventional toilet at 1.6 gallons per flush, if flushed 4000 times in one year, will use 6,400 gallons. At $2/1000 gallons, this will cost approximately $12.80 per year.

The low flow toilet at 1.28 gallons per flush, if flushed 4000 times in one year, will use 5,120 gallons. At $2/1000 gallons, this will cost approximately $10.24 per year.

Therefore, replacing an old toilet with a 1.6 gpf model will save the household $19.20 per year. Since the cost of the toilet is $227, it will take 11.8 years for the new toilet to pay for itself. If the toilet were already being replaced, then there would be no additional cost, because all American toilets now have flow rates of 1.6 gpf or less. Therefore, payback period would be zero years in this case.

Replacing the old toilet with the 1.28 gpf model will save the homeowner $21.76 per year. Since the cost of the toilet is $364, it will take 16.7 years or less fo the toilet to pay for itself. If already replacing the old toilet, you would onlyneed to consider the additional cost of the low flow toilet, or $137 ($364-227), because it is the premium for a more water efficient model. In this case, the toilet would pay for itself in 6.3 years.

Should I Buy a New Toilet?

So, the important question here is: how long will the new toilet last? Will the toilet pay for itself during its lifetime? An average toilet can last up to 30 years without being replaced. This means that in all of these cases, the new toilet would generate cost savings long beyond the payback period.

However, 30 years is a very long time, and you may not intend on living in the home for too long. If this is the case and the old toilet still has a few years left before it needs to be replaced, it might be smartest to look into cheaper options than replacing the toilet. For example, as I mentioned before, a simple plastic bottle filled with sand could lower your toilet's gpf. A tank bank costs less than 10 dollars and could save up to 0.8 gpf.

Other options include installing an adjustable flapper or fill cycle diverter. Check out this article to learn more about low cost toilet retrofits.