Hot Water

April 21, 2015 by


The other day, my son asked about swapping out his current hot water system to an electric hot water tank.

He currently has what is called an indirect hot water heater that uses a zone off his oil fired boiler to make hot water. (See diagram)

There were a number of reasons why he considered doing this.

First, he has electric solar panels on the roof of his house which have lowered his electric costs significantly, so he thought an electric hot water tank might save money.

Second, in the winter, he had issues with his existing system providing enough hot water when he needed it for his morning shower.

Lastly, in the summer, he felt it was not efficient for the boiler to come on and heat up boiler water so it could produce hot domestic water.

electrical-hot-waterHe thought that maybe a stand-alone electric hot water tank (see diagram left) could cost less, provide consistent hot water, and be more efficient.

He asked me what I thought.

Before I tell you what I told him, I want to point out that  there is no simple answer. There are many variables in determining the ‘best’ way to produce hot water.  Variables, like what kinds of fuel are available, what type of budget one has for the initial cost of the equipment, monthly usage cost, and annual maintenance cost.  Also, where he lives enters into fuel costs and availability of expertise in the various solutions.  Other variables are family size and  hot water usage or demands.

Finally, technology and efficiency standards are constantly changing so the answer depends on when he wants to make this change.

To compare heating options, I first need to define a term called BTU’s (British Thermal Unit).  A BTU is a measurement of energy and is defined as the amount of energy to raise one pound of water 1 degree Fahrenheit.  Or for those who are visual, one BTU is equal to burning one kitchen match.

I will limit this analysis to the most common fuel types.  If we look at just cost per BTU, natural gas is the first choice, followed by fuel oil and then propane and electric.

However, fuel costs are seasonal and they vary significantly over time and within the US.fuel-oil-costs

The chart on the above shows that  fuel oil costs for the past two years varied from $2.75 per gallon to over $4.00 per gallon.


If we look at propane prices over the past two years (below), we see a big spike to $4.00 per gallon in the winter of 2013-2014 and a leveling of costs in the winter of 2014 – 2015 to around $2.30 per gallon.Propane-costs


Natural gas is measured in cubic feet.  Prices fluctuate with demand, so it goes up in the winter time (see below)Natural Gas costCurrently, natural gas prices are very low.  In the last year, prices varied from a low of $9.49 to a high of $17.39 per thousand cubic feet.

Electric costs are measured in kilowatt per hour or kWh.  The costs vary seasonally and throughout the US (see below).  electric cost

The US average is 9.94 cents per kWh.  However, if you live in New England, where my son lives, the cost can vary from 15.94 cents to 20.45 cents, a significant difference.

To compare fuel costs to heat water, we need to determine the BTU’s in a unit of fuel.  Then we also need to take into account two efficiency factors. One is the efficiency of taking the energy in a unit of fuel to BTU’s. And the other is the efficiency to heat water with those BTU’s to the desired hot water temperature.

Below is a chart of the BTU’s in each fuel type and efficiency in converting it to BTU’s. This chart calculates the cost for a million BTU’s using the low and high prices throughout the heating season and various parts of the US.

Unit cost Cost per million BTU’s
BTU’s Units Low  High  Eff. low high
Natural Gas 1,028,000 mcf $9.490 $17.390 82% $11.26 $20.63
Oil #2 138,000 gal $2.900 $3.550 82% $25.63 $31.37
Propane 91,800 gal $2.400 $4.000 82% $31.88 $53.14
Electrical 3,412 Kw $0.098 $0.245 100% $28.84 $71.81

But we still have not made hot water. We only have cost per BTU. Let’s now apply the second efficiency factor to those BTU’s to make water. To get this efficiency, we need to know the input water temperature, the output temperature, the heat loss of the tank, the efficiency of the burners or elements, and heat transfer efficiency.

This can get complex.  However manufactures of hot water systems do provide this data for their equipment. To find it, read the specifications for the system or look for it on a tag that is normally attached.

For my analysis, I’ll simplify it and use the following percentages: fuel oil and gas efficiency hot water tanks are in the 60 – 65% efficiency range; electric hot water tanks are in the 90 – 95% range.

To compare costs for hot water, it really does not matter what we assume for usage, as long as we apply the same usage to the various fuel types. The data is valid for comparison purposes.   I will use 70 gallons of hot water per day for a family of four, input water temperature of 60 degrees, output temperature of 120 degrees which requires 16.3 million BTU’s per year.   The chart below shows the range of low and high annual cost.

Cost  1 million BTUs. Annual cost
BTU’s Units System Efficency low high low high
Natural Gas 1,028,000 mcf 0.62 $18.16 $33.27 $296 $542
Oil #2 138,000 gal 0.62 $41.33 $50.60 $674 $825
Propane 91,800 gal 0.62 $51.42 $85.71 $838 $1,397
Electrical 3,412 Kw 0.92 $31.35 $78.05 $511 $1,272

The bottom line is that for tank type heaters, natural gas is best.  Fuel oil is second best and propane and electric the most costly.

So, what did I tell my son?  Since, he already has a indirect system using his fuel oil fired boiler, the additional cost of getting hot water in the heating season is very small.  So, I told him that replacing his fuel oil indirect hot water tank with a classic electrical hot tank will not be a good idea. His solar power electrical panels may produce electricity cheap, but a hot water tank would exceed the capacity of his panels, causing him to extra kilowatts from his local electric company.

However I should also point out that there are newer technologies on the market.  Tankless hot water, or on demand, systems have been on the market for some time and electric hybrid heat pump hot water tanks are now available.   There are also solar heaters and drain-water heat recover systems.  These systems may offer cost benefits over today’s classic solutions.

There is no simple answer to what is the best way to get hot water.  Below you can find pointers to various websites that I used to answer my son’s question.  You can use them to get an ideal on how to determine the best answer for your own situation.

What is a BTU: and

How much water average homes uses:

Average electrical cost –

Selecting a new hot water heater:

To calculate cost of fuel to generate BTU’s:

Average hot water usage and cost per year:



This blog was written by Fred Wilbur. Fred was an employee of Keith Specialty Store from 2005 – 2015 and today enjoys sharing information to help people have a better life.

Why Use Proper Case?

September 15, 2014 by

Today’s world of text messaging, Face Book posts, Twitter tweets, and smart phones applications have many people using only lower case letters in their communications. This blog entry is to point out a problem that may convince you to use appropriate upper case when you fill in an order form.

Consider the example:  “apt l06”.

Is this Apartment “106” as in one hundred and six, or is it “L06” and in “ell zero six”?

Depending on the font used to translate your entry, the number one is hard to distinguish from the lower case letter “L”.

So, if you live in apartment number one hundred and six , and if you write your address as Apt 106, I can assume since you capitalize the letter “A” in “Apt”, that the “1” in “106” is, in fact, the number one.

But if you lived in apartment number “L06” and you wrote: “apt l06”, what assumption can I make from the “l” in “l06”? Don’t say I should just cut and past the characters into the address line, for that just pushes the problem to the person delivering the package.  If you wrote:  “Apt L06”, I would have no question nor have to make any assumptions.

What prompted me to write about this case issue? I got an order to send something to a military base and they had an address line of “mfc llc”.  Initially I thought it was some military acronym and wrote the address as “MFC  11C”. But my co-worker pointed out that the “11c” was actually the LLC and the ‘mfc’ was the company name.

A day later, I was setting up an application on my smart phone to allow me to deposit checks into my bank account using the phone’s camera.  The instructions said that my user ID was the characters: “l006 followed by the characters I entered for my ID.  I had a number of failed attempts to log in until I realized that maybe the first character may be the letter ‘L’, not the number “one”. When I tried the ID with the letter “L” it worked. To even hone in the point, the first letter had to be the upper case “L”.  G0 f1gure!

Oil Burner Electrodes

September 20, 2013 by

Here is an answer to an often asked question.  Oil Burner Electrodes can vary from furnace to furnace and are not always obvious with the furnace burner and serial number as burners are sometimes exchanged by service professionals from the original.   Therefore the electrodes might have been changed and need to be matched with that burner.     Sometimes burners change within model numbers too.    We have found the best way to find which oil burner electrodes you need to purchase is to match the electrodes by shape and size. We do not have a simple way to identify them from your oil burner model number.

Other than shape, there are three measurements you need ;  The diameter of the porcelain, the length of the porcelain, and the distance from the end of the porcelain to the end of the tip (measure straight – not along the bends). See diagram on picture attached/below:
Inline image 2
We carry a wide number of popular electrodes but we do not carry all of them. We can special order some that we do not stock.  We have listed our supplier’s catalog pages on our website that you can use to match up against yours.  Look at the two pages : and If your browser shows these pages too small, often if you click on  it, your browser will enlarge the picture. You can also hold down the CTRL key and press the + sign to zoom in (holding the CTRL key and pressing the – sign zooms out.)
If you find a electrode on either of these pages that match yours, send us the ‘Cat. No.’ and we will get you a price and availability. Ignore the prices on these pages, they are not accurate.
If you cannot find a electrodes that match yours on our website page or on one of the two supplier’s catalog pages, then we most likely cannot get it.
Hope this helps,
Please review your shopping experience – review our store.Keith Specialty Store 
800-705-8838 (within the US)
724-397-8838 (outside the US)
724-397-2228 FAX

Estimated Shipping

March 15, 2013 by

Please be advised that our shopping cart estimates some products. These are mostly large items that require either freight delivery or can not be sized correctly shipping via UPS.  We try to set estimates to be close to what actual shipping costs are, but there are times where we just have to guess.

When we get the order with estimated shipping on it, we determine the exact shipping charges and if it is under the estimate, we will ship it and adjust shipping charges to match the actual cost. We will refund the difference between what the shopping cart authorized and the actual cost.

If the actual shipping charges are more than the estimate, we contact you (via email and/or phone) to get your approval before we ship. If you paid with a credit card, we also have to get your credit card information, for our staff does not have access to your credit card information. We do this for security reasons.

The problem occurs when we can’t reach you or you provided invalid contact information.  In this case we are stuck between a rock and shipping truck.  If the order appears to be time sensitive, we feel badly that we have to hold up the order to  resolve the additional shipping costs.  You can help by providing correct contact information, making sure you listen to our voice messages and make sure our emails do not end up in your spam trap.

We continually work to improve our shopping cart in order to avoid this dilemma,  but until we resolve it, be advised your order may be delayed.

Submersible pumps – 2 or 3 wire?

June 1, 2011 by

Submersible Water Pumps, 2 or 3 Wire.  What is the Difference?

 Submersible pumps, the kind of pump that goes in your well or cistern, are available with two wire motors or three wire motors.  There is also another ground wire which is not counted, so if you look at the pump the actual number of wires will be three or four.  The two wire pump will have two black wires and one green ground wire.  The three wire pump has a black, red, yellow and green wire.

You are probably thinking, “That’s nice, but what is the difference to me?”  The main difference is the three wire pump uses a separate control box which includes a capacitor and relay to start the pump.  The control box is located inside your house or pump house.   The two wire pump does not use a control box.  Everything is built inside the motor of the pump.  All motors larger than 1 ½ HP are only available in the three wire version because you need the control box to start the heavier motors.  Most residential pumps are smaller horsepower.  Our top selling pump is just ½ HP.

Many years ago we sold mostly three wire pumps.  We believed that having a separate control box above the well would sometimes save people the time and expense of pulling the pump when they experience a problem.  If the problem is in the control box it is a simple and relatively inexpensive fix to replace the box, as opposed to pulling the pump and replacing the motor or whole pump.  This is the main advantage of the three wire pump.  Then, probably 25 years ago, a local plumbing contractor insisted he had far fewer problems with two wire pump systems.  We slowly shifted to selling more two wire pumps and our experience seemed to agree with the contractor’s observations.  Also, two wire pumps are less expensive, the wire used to install them is less expensive and the installation is easier because you do not have to wire through the control box.  Of the pumps we now sell, at least 90% of them are two wire.

Which size wire and breaker do I need for an electric water heater?

May 31, 2011 by

Which size wire and breaker do I need for an electric water heater? 

The wire and breaker size depend on which heating elements are in your water heater.  Find the watt rating  for the elements.  This rating is usually on a tag on the side of the water heater.  It is also printed on the elements.  You can find the elements on the side of the heater under a plate attached with one or two screws.

For elements up to and including 2500 watts, the minimum wire size would be 12 gauge.  With 12 gauge wire, use a 20 amp breaker or fuse.  For elements over 2500 watts you must use 10 gauge wire and a 30 amp breaker or fuse.   It is important to match the wire size to the correct breaker or fuse.  The breaker protects the wire from overheating.  You can use 10 gauge wire for lower wattage water heaters.  If you are running wire for a new water heater, it is a good idea to use 10 gauge so that you are covered for any water heater you might buy in the future.

You can find wire on our web site at:

Electric Hot Water Heater – Elements

May 14, 2011 by

How Do I Determine Which Element I Need for My Electric Water Heater?

 If you run out of hot water faster than you used to, have only lukewarm water or no hot water at all, it is possible that one of the elements needs to be replaced. How to accurately diagnose a faulty element is a topic of another post.  This post assumes you have already determined that you need new elements.  It discusses how to determine which element you need and how to replace them.

There are two types of elements found in the majority of water heaters:   a flanged element or a screw-in threaded element.  There are some other types on older heaters, but they are becoming very rare.

Flanged hot water element Flanged Element 

Screw in hot water element Screw-in Element           

Hot Water Element socket wrench Socket Wrench


Always turn off the power supply to the water heater and drain the water from the tank before working with the elements.  Most water heaters have two elements while some have only one.  The elements are located on the side of the tank behind a metal plate attached with one or two screws.  Remove the plate.  There will be two wires attached to the element.  Loosen the screws and remove the wires.  Don’t worry about remembering which wire went to each screw, it doesn’t matter.  It will now be obvious which element you have.  If you see four bolts, it is a flanged element.  Remove the bolts and pull the element straight out.  If you have a screw-in element, you will see a single large hex head on the element.  A 1 ½” deep socket can be used to remove the element or you can purchase an element socket wrench.

The wattage and voltage will be printed on the head of the element.  Some elements will have two different listings such as 3500W at 208V and 4500W at 240V.  Use the larger number when ordering.  You may want to replace both elements while you have the tank drained, even if only one is bad now.

Important reminder!  After installing the new element, always refill the tank with water before turning the power back on.  Open a faucet while you fill the tank to be sure there are no air pockets remaining inside the water heater.  Since elements are made to be submersed in water, they will burn out in seconds if you turn on the power to the tank before it fills completely.


Other informational sources:

  •  A diagram of hot water tanks – from
  • Good video on replacing an element.  Note: this video does not discuss filling the tank with water before turning on the elements.
  • Another source of how to change an element from

What is a limit switch and why does it shut off my furnace?

April 25, 2011 by

What is a limit switch and why does it shut off my furnace?

Trane SWT 01635 thermal limit switch,

photo of item KSS#72-092

The limit switch is a small, silver bi-metal disc about the size of a dime or quarter which turns off the furnace if the temperature inside the furnace gets too hot (see another example)  It is a safety device and should not be disabled or bypassed.  Limit switches do go bad sometimes, especially if the furnace routinely overheats.  However, you should try to determine why your furnace is getting too hot before you replace the switch.  An overheated furnace is usually the result of inadequate air flow through the furnace or a furnace that is too large for the building.  An overheated furnace is not only inefficient, it will shorten the life of the heat exchanger in the furnace.

The first thing to check is your registers.  Make sure all registers are open and not blocked by furniture or other items.  Be sure the filter in the furnace is clean.  If you have recently added air-conditioning to your system, it may be possible to increase the blower motor speed.  Get a furnace technician to do this if you are unsure how to safely change the speed.

If you have tried all of the above and replaced the limit switch but the furnace still overheats, the size of your ductwork or furnace is suspect.  Do you have at least as much cold return air coming back to the furnace as there is warm air going to the home?  If not, add more cold air runs or increase the size of existing runs.  You may also need more warm air runs to get the heat away from the furnace.  The main trunk or ductwork may be too small to handle the needed air flow.  Call a trusted HVAC technician to do a heat loss and/or heat gain assessment for your house to see if the ductwork and furnace are properly sized.

More information can be obtained at the links below:

More about high limit switches at

Interesting forum entry regarding limit switch on

Duct tape, ductboard tape, flex duct tape-what is the difference?

April 25, 2011 by

Duct tape, ductboard tape, flex duct tape-what is the difference?

You might have heard the joke that all a DIY person needs is duct tape and WD40.  If something is supposed to move and doesn’t, use the WD40.  If it moves and isn’t supposed to, use the duct tape!

Before the advent of fiberglass ductboard and insulated flex duct, gray cloth duct tape was pretty much all we needed for tin ductwork and a million other uses around the home, and it is still great stuff to have on hand.  Today there is also ductboard tape, sometimes called aluminum foil tape, as well as flex duct tape.

As the name implies, ductboard tape was designed to construct and seal fiberglass duct work.  This tape is pressure sensitive which means you must go over it with a small squeegee to make a good seal.  Ductboard tape is available with or without the UL 181 approvals.  The UL 181 is clearly marked on the outside of the tape and must be used when the ductwork will be inspected.  Surprisingly, the non-UL 181 tape has a higher adhesion rating than the UL 181 approved tape.  Most of our local contractors prefer the nonlisted tape unless a job must be inspected.  Our flex duct tape is a very sticky, black tape designed to bond, protect, hold and patch flexible duct pipe.  Flex duct tape is not recommended for metal duct.

Now you can get the right tape for the right job.  We will discuss the WD40 later!

Baseboard BTU’s

April 25, 2011 by

Often we are asked how many BTU’s are in a foot of baseboard heating.

To answer this, the following must be considered:  is the baseboard heating system electric, steam or water?  For this post we limit it to hot water baseboard.

Finding (1) the temperature and rate of the water passing through the baseboard, (2) the size of the copper tube and (3) the specifications of the baseboard from the manufacturer will provide a more precise answer.

We sell Argo Low Trim II baseboard which can produce 570 BTU/hr at a water temperature of 180 degrees, at a pump rate of 1 gal per minute.   You can find this information at Argo’s website for Low Trim II.

This amount of BTU’s per foot, combined with a heat loss calculation, can determine how many feet of baseboard are needed to heat a room. Heat loss calculation is a complicated number to determine.  It involves knowing the average outside winter temperature, how the room is insulated, square footage of the room, and number of windows and doors.  There are heat loss software programs that are used to input all the variables to get a result of  BTU’s required to heat a room or house.   One can use a rough estimate of 50 BTUs/hr per square foot.  Keep in mind that a rough estimate is just that, an estimate.

An example is that if you have a room that is 20 x 24 and are trying to determine the amount of baseboard, a rough estimate of BTU’s required would be (24×20)  *50 BTU’s/hr = 24000. The number of baseboard feet would be 2400 / 570, or 42 ft of Argo baseboard.

Baseboard is often installed under windows. Can you guess why?  Look for future posts to get the answer.

Links that provide more information:

  • Article containing more complexities of answering the same question:
  • Interesting conversation regarding baseboard BTU’s –


Get every new post delivered to your Inbox.