How Much Does Your Shower Actually Cost? Shower Cost Calculator 2019

Ever wonder what the cost of each shower you take is? Here is an easy to use and customizable calculator that allows you to calculate your per shower cost and annual showering expense. Using U.S. averages, in 2019, the average shower costs about $0.57 if you use an electric hot water heater, or $0.40 for those heating with natural gas. However, costs can very significantly. So use this tool to more accurately understand your own costs and also how you can save on each shower!

Green Geek Shower Cost Calculator and cost savings from using a water saving shower head

You can get started finding a more accurate estimate of your showering cost by using a number of the averages already provided in the tool – like average electricity cost and shower temperature. Then further refine your calculation with your own specifics – like shower length, shower head flow rate, and how often you shower.

Once you know how much your shower actually costs, you can also calculate the potential savings if you used a water saving shower head. If you’re interested, you can find out more in the original post that led to the creation of this shower cost + potential shower savings calculator.

Overview:

Download the shower cost calculator to estimate your showering expense  Download the Green Geek Shower Cost Calculator

Get going right away by downloading the Shower Cost Calculator spreadsheet above.

Note: You really don’t need to read much more to start using the shower cost tool now. Most of it should be intuitive. The content below is mostly for those that like to geek out on all the little details and/or those that like a little more explicit direction. Hope you have fun calculating your shower costs!

Using the Shower Cost Calculator

Here are a number of helpful tips to use the shower cost calculator tool.

1. Choose your water heater type and calculation units

At the bottom of the shower cost calculator, you will see four different tabs. These separate worksheets provide an appropriate calculator for different scenarios. You can choose your water heater type, either electric or natural gas, as well as the desired inputs and outputs, either imperial – for the U.S., or metric – for the rest of the world. Select the scenario that’s right for you.

Shower costs based on electric or gas water heater and in metric or imperial units

Choose the right spreadsheet tab based on your water heater type and desired units.

All four of these scenarios are prepopulated with average values based on U.S. averages where available. If a reliable U.S. average couldn’t be found, specifics for Richmond, VA USA were used for imperial calculations, and Toronto, Ontario Canada for metric calculations.

2. Basic inputs

Below are the basic inputs for all four scenarios of the shower cost calculator and how to come up with your own customer numbers.

shower cost calculator basic inputs including shower length, shower head flow rate, electricity cost, and water cost

Basic inputs for shower cost calculator.

i. Length of shower

This one is pretty easy. Just use a stop watch time time a number of your normal showers and use the average shower length here. The average shower in the U.S. is 8.2 minutes long.

ii. Current shower head flow rate

To find your current shower head flow rate, look for a GPM (gallons per minute) number somewhere on the shower head. You may need a stool to look up around where the shower head screws onto the shower or it could be on face of the shower head. Regardless, look around and you should be able to see how much water it uses every minute and plug it into this field. If you have two or more showers, take the average of all your showers.

iii (a). Cost of electricity, per kWh (for electric hot water heaters)

For electric hot water heaters, calculating the cost of electricity in kWh (kilowatt-hours) is often not as straightforward as one may think. Most electricity bills have tons of different line items, and while one may be called “electricity” or “kWh cost”, in reality almost all of these line items are actually directly tied to how much energy you use each month. Thus, to calculate your cost of electricity per kWh, take the total cost of your bill for one month and divide it by the total kWh indicated you used that month. Your custom $/kWh number will get better if you are able to calculate the total cost divided by the total kWh over a few bills, but a single bill is still a pretty good starting place. The average cost per kWh in the U.S. is around 12 cents, but this can vary a lot state by state.

iii (b). Cost of natural gas, per cubic foot (for natural gas water heaters)

For natural gas hot water heaters, calculating the cost of natural gas is done in much the same was as the cost of electricity above. Simply add up the total cost of one or a few gas bills and divide that by the total natural gas usage from those bills.

The catch here is that many natural gas bills will report usage not in cubic feet but Ccf, Mcf, or Therms. Ccf = 100 cubic feet, so just divide your cost per Ccf by 100 to get a $ / cubic foot. McF = 1,000 cubic feet (so divide my 1,000) and a Therm or BTU (British Thermal Unit) of natural gas also equals about 1 Ccf, so divide your number by 100 to get $ / cubic foot. (If you have some other unit of measurement, just do a quick google search to find the conversion to cubic feet.)

iv. Cost of water, per gallon

To find your cost of water per gallon, again, get a copy of your water bill and a few bills. Take the total water costs of those bills and divide this by the amount of water used. Be extra aware of the costs of wastewater fees. While technically a single gallon of water out of the tap may only cost you a fraction of a cent, most times you will be charged about that same amount or more for wastewater treatment fees. The water utility only has a single meter on the water going into your house and doesn’t technically know how much they have to treat as sewage from you. However, they typically assume that most of the water you use is going back down the drain which returns to the municipality to clean and they charge you a fee for this for each unit of water you bring into your house. Searching online for average water prices often bring up just the incoming water costs, rather than including these wastewater fees that are essential for knowing your true cost per gallon (or litre).

Similar to natural gas, your water bills will rarely be in individual gallons, but instead may be in cubic feet or Ccf. Here are some quick conversions to gallons for those units: if cubic feet divide by 7.48052 for gallons, or if Ccf divide by  748.052. For metric folk, there are 1,000 litres in a cubic meter, so simply divide by that (isn’t metric so much simpler!).

3. Results

After entering those basic inputs above, you’ll be able to see the results. Specifically, the calculated cost of each shower you take currently. You’ll be able to see the breakdown between the cost of the water and the cost of the energy to heat the water for your shower, along with the actual amount of water and energy used for each shower.

calculated cost of each shower with water cost and energy cost

Calculated cost of each shower.

Once you know your cost of each shower, in the section below you’ll see results on the savings potential with switching to a water saving shower head that still gives an awesome shower! You can see the potential water, energy, and cost savings with making a switch, along with the carbon emission reduction equivalent for this simple change.

Shower savings for each shower when switching to a water saving shower head

Calculate potential savings for each shower.

In the savings section 2, enter your estimated showers per week, and then how many weeks you’re typically home per year (considering most people get away on vacation every now and then), and you’ll be able to see the annual impact. In savings section 3, you’ll see the longer term impact of making a change to a water saving shower head, which really adds up for most people. You can customize both the period of time and the expected rate of return (I use 7% for all of my future value calculations which you can read more about at that link if interested).

Long term savings from changing to a water saving shower head

See savings over the long term. A small change like this can really add up!

Last but not least, if you enter the cost of a new water saving shower head in the section at the bottom of the spreadsheet, you’ll see how quickly this change will pay back. Most people will find a new 1.5 GPM (gallon per minute) shower head is under $30 (like by two favorites: Kohler & Speakman) and the purchase will pay itself back in a matter of months.

4. Advanced inputs: “Utility Variables”

This section is totally optional, but if you want to take things to the next level, consider adjusting these values as well. If you scroll to the top right-hand side of the shower cost calculator you’ll find these more advanced ways to adjust the calculations in a “Utility Variables” section.

Shower cost calculator advanced variables including temperature of shower, temperature rise, heating required, energy required

i. Incoming water temperature (cold tap)

The temperature of the incoming water can really have a significant impact on the energy needed to warm your water. Consider for example that in the middle of winter, that ground temperature around you water pipes may be as cold as 44°F and then could be over 75°F in the peak of summer. (Especially in a place like Richmond where a lot of the water pipes are buried at only 18″ deep.) Below is a great graph from the folks over at builditsolar.com that shows this annual change in ground temperature at different depths.

ground temperature variation at different depths based on time of year and how it impacts water heating and energy used for showering

Ground temperature at different depths based on time of year.

That ~30°F difference means your hot water heater has to put in a lot of extra energy to bring your incoming water up to shower temperatures in the middle of winter. I have all of the energy usage in my house sub-metered and down to the 1-minute level, and have personally found that we use exactly twice as much energy in the winter to heat our hot water than we do in the summer.

Now the important element here is not so much the winter to summer variation as the average incoming water temp based on geographic area. The average incoming water temperature should be a lot warmer for people living in Texas than those living in Maine. What we’re really looking to input here is our best guess at the mean annual incoming water temperature.

Below is a graph that shows these annual averages for inlet water across the U.S. (and an assumed average for Canada of 37°F, although southern portions of many provinces look like they’d be warmer). That’s probably a good staring place based on your location if you don’t want to measure your cold tap water temperature weekly for an entire year.

Average inocming water temperature across the U.S. which impacts showering costs

Average annual inlet water temperature.
Source: http://www.eemax.com/wp-content/uploads/2016/11/Sizing-Map-Sheet-11-2016.pdf

ii. Temperature of shower

From a number of sources online, it seems like there is agreement the average shower temperature is 105°F. Clearly there some variance in this for individuals – I know my wife likes a hotter shower than I do. For my own calculations I just stick with this 105°F, but you could easily bring a thermometer and container into your next shower and collect some water right out of the shower head once you have your shower just how you like and get a better sense of the temperature of your typical shower.

iii. Efficiency of natural gas hot water heater (natural gas only)

If you are using a natural gas tab on the spreadsheet, you will have an additional field that allows you to enter the deficiency of your natural gas hot water heater. While electric hot water heaters are assumed to be 100% efficient (all the electric energy that goes into the water heater is completely transferred into the water), only a portion of the potential energy from the natural gas that is burned in a gas hot water heater will be transferred into heating the water.

The default 61% efficiency is a bit of a conservative estimate and newer models can be considerably more efficient, especially ENERGY STAR models. To improve the accuracy of your calculation, look for the efficiency or “Energy Factor” on the name plate or sticker on your hot water heater that will indicate its efficiency. The value may be something like 0.75 EF, which would mean a 75% efficiency.

5. The calculations

If you have read all the way to this section (or clicked on the link directly to this section), it probably means you are a little extra nerdy. And thus, like me, you may actually be interested in better understanding how all the variables go into the calculation of the cost of your shower. So here’s an example using the default values in the shower calculator in U.S. units:

Your current shower calculation

First, we need to know how much energy is required to heat up a single gallon of water to your showering temperature. This is where we calculate the required increase in temperature from your incoming water temperature up to the showering temp. In the provided example, we’re assuming an incoming temperature of 50°F and a showering temperature of 105°F. 105-50 = a temperature increase of 55°F.

Energy required to increase temperature, and particularly the temperature of water, is often calculated using BTUs. A BTU, or British Thermal Unit, by definition is simply the amount of energy required to raise 1 lb of water by 1°F. We know we want to raise the water temperature by 55°F, so we need 55 BTUs for each pound of water in our example. Further, 1 gallon of water weights 8.33 lbs, so specifically, for each gallon of water we will require 8.33 lbs x 55 BTU/lb = 458 BTUs.

That’s where the BTU calculation ends for electric hot water heaters – because resistance electric heating is 100% efficient, but natural gas hot water heaters are not 100% efficient. So, we need to add an efficiency factor in here. If our natural gas water heater is only 61% efficient, to get 458 BTUs of energy into that water, we will actually need to burn 458 / 0.61 = 751 BTUs of natural gas to get that required heat into our water.

Now, BTUs is great for calculating the amount of energy required to heat water, but electricity and natural gas are not billed in BTUs, so we have to change to appropriate units. Electricity is billed in kilowatt hours, and each kilowatt hour has the equivalent of 3,412 BTUs worth of energy in it. so our 458 BTUs / 3,412 BTU per kWh = 0.134 kWh.

Natural gas we’ll convert to cubic feet, and there are 1,000 BTUs in each cubic foot of natural gas, so 751 BTUs / 1,000 BTUs per cu. ft. = 0.75 cu. ft. of natural gas. For the rest of the calculator the calculations are pretty much the same for both electric and natural gas, so we’ll stick with just the electric example for the rest.

So, we left off an knowing it takes 0.134 kWh to get each gallon of water up to our showering temperature. Next, we need to figure out how much water we use in each shower. By timing our shower and getting the flow rate from our shower head in gallons per minute (GPM), we can quickly calculate the amount of water used. An average 8.2 minute shower with an average 2.3 gpm shower head would use 8.2 min x 2.3 gpm = 18.9 gallons of water for each shower.

At 0.134 kWh of energy needed to warm up each gallon of water for our shower, our average shower will require a total of 18.9 gallons x 0.134 kWh = 2.5 kWh in energy to heat our water.

Now, that we know how much water and energy is used, we simply need to calculate our two costs based on this water use: the cost of the water itself and the cost of the energy to heat the water. By pulling up a number of electric bills and taking the total cost divided by the total kWh usage, we get our average energy cost of 12.3 cents per kWh. By doing the same thing with water bills, and further converting our large water units (like ccf) to gallons, we get a cost of about 1.35 cents per gallon.

18.9 gallons of water used x $0.0135 per gallon of water = 25.5 cents for the cost of water for each shower. Then, 2.5 kWh of energy required x $0.123 / kWh =  31 cents worth of electricity for each shower. Combine those two costs and we get a total average shower cost of 56.5 cents! In doing this calculation, I also found it interesting to see that with an electric hot water heater, the energy to heat the water was actually more expensive than the cost of the water itself (although, your local costs could be different).

Savings calculations

Once you have the cost of your current shower calculated, it doesn’t take much to see how much you could save by installing a water saving shower head.

By replacing our existing 2.3 gpm shower head with a 1.5 gpm water saving model, we reduce our water usage by 2.3 gpm – 1.5 gpm = 0.8 gallons each minute. Given our 8.2 minute long shower, this is 8.2 min x 0.8 gpm = 6.6 gallons of water saved each shower. Using our energy required of 0.134 kWh per gallon of water x 6.6 gallons of water saved = 0.9 kWh savings per shower. Using our $/gallon and $/kWh rates found above, we can see that saves 19.9 cents per shower. With a previous shower cost of 56.5 cents, this represents a 35% savings and a new shower cost of 36.6 cents.

Beyond the cost savings, we can also calculate using the EPA’s great green house gas equivalencies calculator that a 0.9 kWh savings per shower is the carbon equivalent to 1.5 miles driven in the average car. That means with each shower, not only would you be saving water, it would be as if you drove 1.5 fewer miles each day (or however often you shower)!

Now to calculate annual savings, you figure out how many showers you take in that shower per week, and how many weeks that shower is in use per year. In the default values of the calculator we assumed 12 showers a week using that shower (from say 2 people showering 6 days a week), and that for a total of 2 weeks in a year no one would be home showering (and would be staying with family, on vacation, traveling for work, etc.). In this case, annual savings = 19.9 cents per shower x 12 showers per week x 50 weeks a year = $119 saved each year.

To calculate long term savings, our calculation gets a little more complicated as we take into consideration the expected annual rate of return we can generate on those savings. For instance, over 5 years, we are not just simply getting 5 x $119 in annual savings = $595. Instead, we could pay down $119 extra of student loan debt each year that currently has a 6.5% annual interest rate (and thus, our expected rate of return would be 6.5% on these savings), or we could pay off high interest credit card debt at 18% APY (again, we could use this as our rate of return), or we could invest these savings into low cost, broad based index funds or other sound investment options.

For the shower cost estimator, and all future value of money calculations on this site, I assume a 7% expected rate of return, because this is the average inflation adjusted return of the U.S. stock market of the last 60+ years. (Interested in learning more about this inflation adjusted return or doing other future value calculations? You can read about this in more detail on the future value calculator tool page.) I’m assuming anyone in the U.S. can expect approximately these returns over the long run by investing the savings in a Vanguard or Charles Schwab total stock market index fund or the like.

You can select any long term savings timeline in the calculator you like, however, the default value provided is 15. Again, when invested, the savings from this simple actin can be so much larger than 15 years x $119 savings per year (which equals $1,785 by the way). The formula for calculating the future value of something that has an annual payment (or in this case savings) is Future Value = Annual Savings * [[(1 + Interest Rate)^Years -1] / Interest Rate]. In our example, FV = $119 * [[(1 + 0.07)^15 – 1] / 0.07] = $2,990! This is a great example of how little savings can really add up over time!

Now this can be more easily done in Excel or Google Sheets with a simple formula that is =FV(rate, npr, pmt). Which is really =FV(rate,# of years or periods, recurring payment or savings). For our example above we would enter a 7% interest rate, a 15 year period, and an annual payment of -$119 (because these are actually savings instead of an expense), which looks like this =FV(0.07,15,-119) = $2,990.

The above example is a little inaccurate in that it simplifies the calculation as if you are only realizing your $119 in savings at the end of the year, and that you only invest all of that $119 all at one time to get that 7% annual interest rate. Thus, your money is only compounding annually. In reality, you are saving on your shower every single day, and can benefit from weekly or potentially even daily compounding of your savings. So, to take this a step further, we can calculate the scenario where you invest your savings from your lower cost shower at the end of every week. We will be moving our future value formula from an annual basis down to a weekly basis, and as there are 52 weeks in a year, we simply modify everything by a factor of 52. To write this out with an explanation first, it would be =FV(annual interest rate divided by 52 weeks per year, 15 years times 52 weeks per year, $119 in annual savings divided by 52 weeks in a year). In your spreadsheet, this would look like =FV(0.07/52, 15*52, -119/52) = $3,155.

Payback and Return on Investment

Lastly, it’s a straight forward calculation to find out how quickly changing to a water saving shower head could pay itself back. Firstly, find the assumed cost of your new shower head, which I’m assuming is $25.00 here. Then, take $25 divided by your monthly savings, which would be $119 of savings annually (calculated earlier) divided by 12 months in a year = $9.92 in savings per month. So $25 cost / $9.92 per month in savings =  2.5 months to pay back the initial cost.

Now once the initial purchase is paid off, we can see the annual equivalent return that this activity is provided us with. That is, what is the value of deploying these $25 to this water saving shower head project? We know those $25 can get us about 7% in the stock market annually. While in this case, our equivalent annual rate of return is the $119 in annual savings divided by our purchase cost of $25. $119/$25 = 473%! An annual rate of return like that is crazy hard to beat! While it would be nice to invest every dollar with such a high return, it’s at least a no-brainer to use 25 bucks towards a project like this.

Another way you could think of this payback and return on investment: you shell out $25 one time, however, you get it right back in two and a half months, and then in addition, every two and a half months after that you magically get another $25 back for the rest of the useful life of this shower! That is a pretty incredible deal and one that I certainly can’t turn down.

That’s probably more than you ever wanted to think about in regards to something so basic as showering. Hope you get use out of the tool, and as always, I’m happy for your feedback and ways to improve future versions of the tool. Cheers!

Download link

Download the shower cost calculator to estimate your showering expense  Download the Green Geek Shower Cost Calculator

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