Some Thoughts on Water Consumption

One thing all of us consume all of the time is water, whether it comes from the tap, flows out of the shower head, gets flushed straight down the toilet, or is cycled through our washing machine or dishwasher.

That water has a real cost. In my town, for example, there is a charge of $4.35 per 1,000 gallons of water consumed, plus an additional charge of $4.35 per 1,000 gallons of water discharged into the sewer system. However, there’s a 7% tax on top of that figure, bringing to total to $4.6545 per 1,000 gallons for usage and $4.6545 per 1,000 gallons for the sewer. That means our total charge is $9.31 (rounded from $9.309) per 1,000 gallons of water that flows through our house or $4.65 (rounded from $4.6545) per 1,000 gallons of water that we drink or use in food preparation.

You can (almost always) find your water rates on the website of your city or your water provider if you you want your own numbers for comparison’s sake, but for the sake of this post, we’ll be using our family’s numbers.

What about hot water? There are so many factors involved here that I’m just going to stick with the answer from Ask Mr. Electricity, which states that it costs about $0.01 to $0.02 to heat a gallon of water. I’ll average that and assume that the cost of heating a gallon of water is $0.015.

So, what do those real numbers mean when it comes to household tasks? I ran through some calculations on our normal behaviors at home to see what the impact really was.

Taking Showers

Right now, five people live in our house. Let’s assume that all of us take a shower each day (which is pretty true on average throughout the year – I’d say it’s slightly less frequent in the winter and slightly more frequent in the summer) and that those showers take ten minutes each (I probably take the shortest showers; my daughter takes the longest ones).

The shower head in the most frequently used shower in our home puts out about 1.5 gallons of water per minute. We’ll also assume that we take warm showers, so half of the water used is hot water and the other half is cold (this is a rough estimation).

So, that’s 50 minutes of showering each day. If our shower head puts out 1.5 gallons per minute, that’s 75 gallons of water. Again, we’ll assume half of it is hot – 37.5 gallons – and half of it is cold – 37.5 gallons, too.

Our cost per 1,000 gallons of water is $9.31 for both water and sewer combined. So, for using 75 gallons of water, that’s about $0.70. That’s the total cost for our family’s water usage in the shower per day. In addition, 37.5 gallons of that water is hot and we estimate that it costs $0.015 per gallon to get that water hot, so our total cost for water heating is $0.5625 – or $0.56.

Thus, our family’s total daily water cost for showering is $1.26. Over the course of a month – 30 days – that adds up to $37.80 in water use for our family for a full month of showering.

What kind of impact would various simple changes have on that water use?

A lower-flow showerhead Our shower head is already a relatively low flow one, but let’s say that we switched to this well-regarded 1.25 gallon shower head. With 50 minutes of showering a day, this shower head would cut our daily water usage from 75 gallons to 62.5 gallons. This cuts our daily cost for water use down to $0.58. For hot water, we’d only be using 31.25 gallons of hot water, so our cost for water heating would go down to $0.47 per day. Thus, our revised daily water total cost for showering would be only $1.05, totaling up to a monthly cost of $31.50. We’d save $6.30 a month in water usage due to that shower head, or $75.60 per year in savings. That’s not bad at all, provided it didn’t cut down on our water usage costs. A lower-flow shower head can save money (on the order of $6-7 per month for a family of five) for almost anyone that takes daily showers, provided you don’t mind a somewhat reduced flow of water in the shower.

Shorter showers What if we cut everyone down to seven minute showers instead of ten minute showers? Basically, we’d just cut our total cost by 30%. Right now, it’s $37.80 a month, so our cost would go down to $26.46 per month for water use for showering. That’s a savings of $11.34 per month, or $136.08 per year in savings. My conclusion is that shorter showers can save worthwhile money if you institute them in a larger family, but if you’re single, they won’t save a whole lot of money (maybe $2 or $3 a month, depending on how much time you cut out).

Doing Dishes

For the discussion of washing dishes, I’m going to use numbers from this Treehugger article:

1. The average dishwasher uses 6 gallons of water per cycle.
2. The average Energy Star-rated dishwasher uses 4 gallons per cycle.
3. Their energy use ranges from 1.59 kWh per load down to 0.87 kWh per load. (We’ll assume the high number applies to the average dishwasher and the low number to an Energy Star dishwasher, for calculation’s sake.)
4. The average kitchen sink faucet flows at 2 gallons per minute,

We’ll also assume that the water in a dishwasher cycle is purely hot water and that our energy company charges $0.12 per kilowatt-hour for energy.

Let’s translate those numbers into dollars and cents.

The average dishwasher uses 6 gallons of hot water per cycle. Our water cost is $9.31 per 1,000 gallons and we pay an extra $0.015 per gallon of hot water. Thus, our total water cost for an average dishwasher load is $0.15. This dishwasher also uses 1.59 kilowatt hours of energy at a cost of $0.12 per kilowatt hour, adding another $0.18 per load, giving us a total cost of $0.33 per load for an average dishwasher.

The average Energy Star-rated dishwasher uses 4 gallons per cycle. Again, using the above water costs, we’re essentially reducing the cost by a third. Thus, the total water cost for an average dishwasher load is $0.10. This dishwasher also uses 0.87 kilowatt-hours of energy at a cost of $0.12 per kilowatt hour, adding another $0.10 per load, giving us a total cost of $0.20 per load for an Energy Star dishwasher.

So, right there, you’ll save about $0.13 per load in energy and water use with an Energy Star dishwasher with good numbers versus an “average” dishwasher. This is well worth comparing when looking at a replacement dishwasher.

What about hand-washing dishes? It really depends on the methods you use. The most efficient method I know of involves washing all dishes in a basin of very hot water, then rinsing quickly with cold water before putting them in the rack. Let’s assume that we put three gallons of hot water in a sink basin for washing, then use two minutes of cold water flow to rinse all dishes before we sit them out to dry.

In that event, four gallons of hot water is costing us $0.06 for the energy to heat it (remember, it’s $0.015 per gallon) and $0.04 to use it (remember, it’s $9.31 per 1,000 gallons for both water and sewer). An additional four gallons of cold water will cost $0.04. Thus, if you use that very efficient method of hand-washing dishes – using a basin of four gallons of hot water to scrub everything, then four total gallons of cold water from the faucet to rinse everything – you’ll only use $0.14 in water and energy total.

Here’s the truth: an Energy Star dishwasher with good numbers on water use and energy use is going to be worth a decent premium when you’re replacing dishwashers. On the other hand, hand-washing dishes can save you a dime or so per load if you’re very efficient with your water, but it’s not particularly time efficient.

Washing Laundry

Another major use of water in our home comes from washing laundry. We do about five loads of laundry per week, given that we have two adults and three growing children in our house. This is an average during the year, as we tend to do more laundry in the spring and summer and less in the fall and especially in the winter.

Some basic facts to work with, using this article from Ask Mr. Electricity:

1. The average normal washing machine uses 40 gallons of water per load for an average-sized load.
2. The average high efficiency washing machine uses 14.7 gallons of water per load for an average-sized load.
3. Half of the water in a load is used on the wash cycle, with the other half being used on the rinse cycle.
4. Warm water in a washing machine is a 50% mix of hot water and cold water.
5. The average normal washing machine uses 0.256 kWh of energy per load, while the average high efficiency machine uses half of that (this isn’t important for water usage, but is worth noting).
6. The average high efficiency washer costs $100 more than the average normal washing machine.

Let’s see what all of this costs us in our house. We have a normal washing machine that came with our house and we usually wash a load of laundry on a warm wash and cold rinse setting. That means we use 40 gallons of water, 10 of it hot and 30 of it cold. It costs us $0.015 per gallon to heat up the water, so that’s $0.15 for heating the hot water. We also use 40 total gallons of water, which costs $9.31 per 1,000 gallons, which gives us a total cost of $0.37. Thus, our water cost for that load of laundry is $0.52 – $0.37 from the water usage and $0.15 from the heating.

What happens if we do the same load in a high-efficiency washer? If we use the warm/cold setting again, we’ll be using 14.7 gallons of water, 3.675 of it will be hot and 11.025 of it will be cold. It costs us $0.015 to heat up that hot water, meaning our cost is $0.06 for heating the hot water. We’re also buying and disposing of the 14.7 gallons of water from the city at a rate of $9.31 per 1,000 gallons, so our pure water costs add up to $0.14. That means that our water cost for a high-efficiency load is $0.20, saving $0.32 per load over a regular washer. That’s a sizable savings.

What if we switch to washing laundry with a cold wash and cold rinse setting? In that case, in a regular washer, you’ll simply be using 40 gallons of cold water, which will cost $0.37. In a high-efficiency washer, you’ll be using 14.7 gallons of cold water, which will cost $0.14. With a regular washer, you’ll save about $0.15 per load. With a high efficiency washer, you’ll save about $0.06 per load.

So, depending on whether you use warm-cold or cold-cold settings, a high-efficiency washer will save you approximately a quarter per load in water costs – a bit more if you’re using warm-cold and a bit less if you’re using cold-cold settings.

This brings us to the big question: does a high-efficiency washer actually pay off in terms of water use and energy use savings? As noted earlier, an average washing machine uses 0.256 kWh of energy, while a high efficiency washing machine uses half of that per load. We pay $0.12 per kWh on average, meaning that the energy cost of a high efficiency load is about one and a half cents in savings. Add that to the approximate savings of a quarter per load in water use and you’re saving about 27 cents per load with a high efficiency washer (again, depending on your specific settings and specific models).

In the end, it would take about 380 loads of laundry to make up for the $100 in price difference between comparable normal and high efficiency washers using the numbers given above. Is it worthwhile? My feeling is that if you don’t tend to get your clothes filthy every time you wear them, a high-efficiency washer will end up saving you money over the long run, but it’s not worth running out and buying a replacement. Make the switch when your current washer fails.

Flushing Toilets

According to this site, the average person uses the toilet six to eight times a day, which averages out to somewhere around 2,500 uses per year per person. In our household, with five bathroom users, that adds up to 12,500 uses per person. If you assume that the toilet is flushed each time, that means 12,500 flushes in a given year.

The first factor that matters is water usage per flush. According to ConserveH20, older toilets could average as high as 7 gallons per flush, but that modern toilets are restricted to 1.6 gallons per flush. If we operate under the assumption that we’re strictly talking about modern toilets, these toilets are using 1.6 gallons per flush.

That means that in a given year, if we flush each time the toilet is used in our home, it’s adding up to 20,000 gallons of water per year. At a cost of $9.31 per 1,000 gallons, that’s a total cost of $186.20 in water for toilet use per year in my area.

Now, let’s look at some alternative strategies to see how much can be saved.

If you were to use a high-efficiency toilet that uses only 1.28 gallons per flush, you’re reducing the total number of gallons of water used per year in our home from 20,000 to 16,000. Thus, a high-efficiency toilet cuts cuts our total water bill by $37.36 annually.

What if we adopt the classic phrase “if it’s yellow, let it mellow”? It’s a well-known idea passed around by water conservationists for decades that simply tells us to not flush the toilet if we’re merely using it to urinate. Let’s assume, then, that this reduces our household flushing to once per day per person, or 1,825 annual flushes. In a normal 1.6 gallon per flush toilet, our water usage drops to 2,920 gallons per year – we’ll round it to 3,000. With our rate of $9.31 per 1,000 gallons, our water bill for toilet usage would drop to only $28 per year. With a high efficiency toilet, that water use drops to $23 per year. That’s a savings on the order of $150 per year for my family.

Another important factor is toilet water leaking, which can sometimes happen if there’s a minor flaw in the toilet’s guts. You can check for this by putting a few drops of food coloring into the bowl and then checking it again in fifteen minutes or so. You can also put a drop or two in the tank and check both the bowl and the tank in fifteen minutes. A slow water leak in your toilet can devour a few gallons a day without you even noticing it, and that can add up to $20 or more a year in lost water. Most of the time, fixing the problem is just a matter of tightening a few things with a wrench.

Lawn Care

This is a messy issue for several reasons.

First of all, according to this article from Pacific Standard, 50 to 60 percent of residential water usage goes toward lawn and landscape irrigation. Seriously. Half of residential water goes into keeping up lawns.

Why? this article from The Week digs into the reasons, including the fact that a green lawn can bump the resale value of a house by 11% and that many people tie a green lawn into their sense of enjoyment of having a lawn at all.

Our solution for watering the lawn is to simply keep it from permanently dying. We allow it to get quite brown during dry seasons, but we try to keep the ground moist enough so that it doesn’t fully revert to a dirt lot. We utilize rain barrels on our property, so if we even get a little rain, we don’t need to water our lawn much at all.

Instead, much of our outdoor water use is directed toward our garden. Based on my calculations, we use as much as 25 gallons of water per day simply on our outdoor gardens over the course of the warmer months. If you figure that there are 200 days where we average 25 gallons of water per day for the gardens, that adds up to 4,500 gallons per year. At a rate of $9.31 per 1,000 gallons, that adds up to very close to $50 per year just to water our garden.

Of course, most of our gardens are productive vegetable and herb gardens, which means that some of that water is going for food production – but not nearly all of it.

What’s the right path to follow here? It really depends on what you value. Economically, it’s definitely worth it to water your lawn when you’re trying to sell your home. It becomes less clear – and depends on personal choice – when you’re not aiming to sell. Regardless, watering your lawn is surprisingly expensive.

Final Thoughts

It’s often amazing how much water use adds up over time around your home. We use water for so many purposes and in so many ways, often without thinking twice about it. There are lots of little tweaks we can make to cut back on water usage without much life impact, such as tightening up toilets, fixing damaged faucets, using a better toilet-flushing strategy, using low-flow shower heads, washing not-very-dirty clothes on a cold-cold cycle, buying efficient housewares and large appliances, and so on.

Water might seem free, but it does have a cost that adds up, one drop at a time. Be mindful of those drops.

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