Tankless water heaters v. Storage tank water heaters

Tankless water heaters v. Storage tank water heaters

In the United States, most homes have storage tank water heaters. The tank typically stores between 30 and 50 gallons, but you can find larger or smaller tanks, depending on your application. Storage tank water heaters are responsible for about 17% of a home’s annual energy usage. In terms of energy consumption, it’s one of the major players in your home.

For years, statistics showed that heating comprised the majority –more than half – of a home’s annual energy usage. With the move toward high efficiency, heating now consumes about 40% of a home’s annual energy consumption. Appliances, water heaters and air conditioning combined have become the major consumers.

Targeting older appliances and fixtures will help reduce your energy costs, and the water heater is a pretty juicy target. But should you go for a tankless water heater? Can you still save money with a tank?

The pros and cons of tankless water heaters

A tankless water heater provides instant hot water, if you can be a little flexible about your definition of “instant.” Instead of storing pre-heated water for use “on-demand,” a tankless water heater creates hot water only when you need it. Some “tankless” water heaters have a tiny tank that holds a small amount of pre-heated water to minimize the “cold water sandwich.” Many tankless water heaters, however, just heat water when you open a hot water tap. The cold water that remains in the pipe is flushed out and soon enough, you’re getting “endless” hot water.

The rating for a tankless water heater shows the number of gallons per minute the water heater can provide. Higher capacity tankless heaters can supply 9 or more gallons per minute of hot water. That’s clearly enough for a shower – which might only take 2.5 gallons per minute of hot-and-cold water mixed. If your shower routinely competes with a dishwasher, a washing machine or another bathroom, the higher capacity water heater may be needed.

The bottom line on tankless water heaters

If you use less than 40 gallons of hot water per day, you can save money with a tankless water heater, but there are some conditions involved! Tankless water heaters are more expensive to buy than a conventional storage tank water heater is – by about a factor of two. You’ll pay twice as much for a tankless water heater, and the installation costs will be higher. Tankless water heaters require a larger gas (or electric) service, so you may need to do some retrofitting of your existing gas or electricity service to supply a tankless water heater.

The good news is that a tankless water heater will last about two to two-and-a-half times as long as a storage tank water heater. Since they’re wall-mounted, you’ll recover the space that your storage tank water heater currently takes up. Another potential positive – they can be mounted on the outside wall of the home.

In terms of operating costs, a tankless water heater can save you between one-quarter and one-third of what you’d spend on keeping stored water hot. Your savings would depend on how much hot water you use in a day. The more hot water you use daily, the less you’ll save. If your household consumes a lot of hot water every day -60 to 80 gallons – you would reduce your savings to 10%-15%.

The pros and cons of storage tank water heaters

Storage tank water heaters aren’t particularly efficient. The tank loses heat in a number of ways. Combustion losses can reduce your tank’s efficiency by 15% or more. Standby losses – heat escaping through the tank walls – reduces efficiency by 30% or more. Transmission losses – heat escaping through the pipes –may reduce your efficiency by another 10%. By the time your hot water exits a tap, you might get only 40%-50% of what you paid for.

Residential storage tank water heaters have a rated life of between 6 and 12 years. You’ll replace your storage tank water heater twice during the lifetime of a tankless water heater. That gives the tankless heater a cost advantage over a storage tank water heater.

Another negative for storage tank water heaters is that they don’t “fail pretty.” Mineral deposits inside the tank can cause uneven heating, overheating, smelly water and noisy operation. A failing hot water tank can discharge rusty water or leak. Any of these signs indicates an impending tank failure. Don’t ignore them!

On the positive side, a storage tank water heater is the cheapest way to provide a source of heated water in terms of immediate, out-of-pocket costs. 40-gallon storage tank water heaters are widely available, relatively inexpensive and can be installed in a day with limited need to modify an existing gas or electrical service. Your operating costs will be higher and your tank may have a shortened life cycle, but if you need hot water today – a storage tank water heater is still a respectable option.

If you’d like more information about tankless water heaters, storage tank water heaters or other water heating options, please give us a call at Boston Standard Company at (617) 288-2911 and we can help you choose the best option for your home.

Photo Credit: Alan Levine, via

New Water Heater Regulations Coming in 2015

Change is constant, especially when it comes to technology and politics. In early 2015, technology and politics will meet in a very unusual place: basements and utility closets throughout the United States. New federal efficiency regulations will go into effect on April 16, 2015, and that means you’ll see some significant changes to your next new water heater.

To achieve these new efficiency standards in gas-fired water tanks that hold fewer than 55 gallons, manufacturers will increase the amount of insulation surrounding the tank. By itself, that’s not bad, but the extra insulation will increase both the diameter and the height of the tank by two inches.

In addition, the new requirements eliminate standing pilot lights. Your current water heater may or may not have a pilotless ignition system. If you don’t have a standing pilot light, you have a mechanical, spark-based ignition. Your new water heater will come equipped with an intermittent, electronic pilotless ignition system. Depending upon the tank’s size, it may also be outfitted with a mechanical damper system as part of the tank’s exhaust, both of which will require the addition of 120 V electrical service.

The addition of electronic ignition means that new gas-fired water heaters will not work during a power outage. Homeowners will need to monitor the status of their storage tanks or connect the tank circuit to a backup power supply to guard against freeze-related damage during prolonged power outages.

For storage tanks that exceed 55 gallons, the addition of a condenser unit is the most likely way to achieve the new minimum efficiency requirements. A condensing water heater will require mechanical damping at the exhaust, electrical control for both the damper and the condenser, and a drain to eliminate condensate buildup.

The design changes to a conventional water tank can cause some logistical problems during replacement. If your current water heater is a tight fit, you may not be able to replace your tank with a tank of the same size. A change in the tank footprint of two inches in diameter and the addition of two inches in height could mean the difference between fitting and not fitting a new tank into an existing utility closet. Increased tank sizes also mean re-plumbing your existing water heater connections along with adding electrical service. For tanks that exceed a 55-gallon capacity, condensation drainage may pose the biggest challenge. If your water heater does not already have easy access to a drain, adding one might be technically challenging at the least, if not impossible in some cases.

The changes also significantly increase the skill level required to replace a water heater. Because water heaters have not changed much in size or design in decades, few or no changes to existing plumbing are required to disconnect an old tank and install a new one. With the new regulations, water heater replacement will require plumbing, venting and electrical skills that likely exceed the competence of the average homeowner. In short, these new tanks aren’t your father’s water heaters.

So what options are currently available for homeowners?

In the next several postings on the blog, we’ll take a look at all of the options that are available for homeowners, and the pros and cons of each choice. In the mean time, if you need assistance with an aging water heater, please call us at Boston Standard Plumbing & Heating at (617) 288-2911 anytime. We can provide a wide range of options for all of your domestic hot water needs.

The Hidden Danger of Water Heaters and Boilers

You don’t hear about it happening very much (thankfully!) but tank-based water heaters and boilers can (and do) explode, often with catastrophic results. Water heaters and boilers are designed to be safe, and are installed in literally millions of homes in the United States. Water heaters and boilers include failsafe devices to prevent the build–up of dangerous pressure levels inside the devices. Occasionally however, the failsafe devices fail.

This slow-motion video, compliments of the Mythbusters television show on the Discovery Channel, demonstrates (safely) what happens when a water heater pressure and temperature valve fails. Although the demonstration involves a hot water tank, the same thing can happen with a boiler. And in this case, size matters! The larger the device is, the more damage it can do!

The failsafe for a water heater or boiler is a device called a pressure-and-temperature valve (PT valve). Some people call them T & P valves – they’re the same thing. The valve usually sits on or near the top of the water tank or boiler and is designed to open when a set pressure or temperature inside the tank is achieved. Some tanks are outfitted with a pressure valve, which opens only when a higher pressure is detected, regardless of the temperature in the tank.

Basic physics says that temperature and pressure in a closed system have a direct relationship. That is, when the temperature goes up, so does the pressure, and vice versa. Turning up the heat on your hot water tank or your boiler control will increase the pressure in the system.

These systems are designed to handle “modest” changes in temperature and pressure. Manually adjusting the temperature upward on your water heater or boiler should never produce catastrophic results. So what can go wrong? Usually a combination of things!

Regulators and thermostats are designed to keep the operating temperature of a device within a specified range. When the temperature drops below the specified range, the regulator turns on the heater to heat the water in the system. When the temperature rises to the top of the range, the regulator turns off the heat. If the regulator or thermostat in the system goes bad, one of two things can happen: no heat at all, or heat all the time!

If the regulator or thermostat gets stuck “on” and heats the system constantly, the T & P valve or pressure valve is supposed to open and relieve pressure build up in the tank. It’s supposed to prevent the tank from ever reaching the point where an explosion is imminent.

Here’s the bad news. T & P valves and pressure valves can fail. Unlike the regulator or thermostat– whose erratic behavior will indicate a failure – there’s no way to know that a PT valve is going bad or has failed without testing it. Fortunately, testing is simple and homeowners should test the PT valves on their water tank(s) every month or two.

The valve (shown in the picture accompanying this post) can be lifted or flipped into the “open” position by hand. If the valve opens and closes smoothly, it’s still doing its job. If it doesn’t open, or opens and closes only with difficulty, it should be replaced. As a rule, PT valves on boilers and water heaters should be replaced every three years, whether they’re working or not. A PT valve is an inexpensive item, and the peace-of-mind is worth every penny.

Don’t underestimate the amount of damage a defective water heater can do to your home. Depending upon its size, a water heater or boiler can build up more than 100,000 pounds of pressure before it explodes. An exploding tank may lift off its base at a velocity of 350 MPH, and will easily shatter the foundation, floors and roof of a home. Unimpeded, a fully pressurized 50-gallon water tank can achieve an altitude of more than 500 feet!

Pressure aside, a hot water tank is also carrying 40 or 50 gallons of potentially scalding hot water, which will be distributed over the tank’s exit path. And then there’s gravity – what goes up must come down! An empty water tank can weigh between 75 and 200 pounds, and when it returns, it may come back down in one piece or it may split into multiple pieces.

Boston Standard Plumbing & Heating can help you perform regular maintenance on your hot water tank and/or boiler, show you how to test your PT valve and provide valve replacement services as needed. Water heaters and boilers can be operated safely in a home, but these devices do require regular professional inspections and maintenance.

Give us a call at (617) 288-2911 anytime to schedule an appointment. Call us if you experience any operating problems with your water heater or boiler – including over- and under-temperature conditions, and pilot light or electronic ignition problems.
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Will A Tankless Water Heater Fit In Your Boston Home? (Part 3)

For the last two weeks, I’ve examined the perspective of cost and operational efficiency of tankless hot water systems. Boston homeowners may not find the savings they were looking for from tankless hot water, but there are benefits other than those you can measure in out-of-pocket terms.

Tankless hot water systems are more efficient than conventional hot water heaters. American homeowners could aggregately reduce carbon emissions by more than 90 million tons annually, just by using tankless hot water systems. If reducing your carbon footprint is important to you, and the cost of a hot water system is the same over 15 years whether you go tank or tankless, this might be enough of an incentive to make the switch.

Tankless hot water systems take up less space in your home. If your basement or utility space is already crowded, a tankless system may help you reclaim some valuable real estate. In the process, you may be able to reduce the risk of water damage to nearby personal property if a water tank fails. Most homeowners insurance doesn’t cover “clean water” damage – that is, damage that’s caused by plumbing failures in the home. A tankless hot water system eliminates the danger of having a 40- 50-gallon instant spill.

Hot water tanks can’t be recycled effectively, so they tend to end up in landfills. By reducing the number of tanks that are discarded each year, Americans could significantly reduce the amount of landfill space required to dispose of their trash. Like reducing your carbon footprint, if reducing your waste stream is important, going tankless may help you do your part.

No matter what you decide, Boston Standard Plumbing & Heating can help. We do hot water heating system installations of all kinds, and we’re always ready to help. Whether you need emergency assistance, routine maintenance or a new installation, call us at (617) 288-2911 anytime!