The Difference Between Storage and Tankless Water Heaters

While offering higher efficiency, tankless water heaters usually don't make sense

There are two primary types of water heaters: storage and tankless. In this column I’ll try to explain the differences between these two approaches and offer some guidance on choosing between them. (There are also “hybrid” water heaters with features of both that I’ll cover in a future blog.)

Storage water heaters

Most water heaters are storage models. These are insulated tanks holding 20 to 120 gallons with either electric heating elements or gas burners. The storage tank stratifies with hot water at the top and cold incoming water at the bottom, so that as you draw off hot water (from the top), you get consistently hot water until the hot water is nearly depleted. The “first-hour rating” tells you how many gallons of hot water can be delivered in an hour.
Storage water heaters constantly lose heat through the tank walls. Even though the tank is insulated, the difference in temperature across that insulated wall is large, so even with a lot of insulation the stand-by heat loss is substantial. Gas-fired storage water heaters that have standing pilot lights replenish some of that lost heat with the pilot, but most of the pilot’s heat is lost up the flue.

Tankless water heaters provide constant hot water and energy savings

To address the issue of standby heat loss and running out of hot water, tankless water heaters (also referred to as demand water heaters) were developed decades ago. These are sometimes (especially in other countries) installed at the point of use, say in a bathroom, but in this country they are usually installed centrally in place of standard, storage water heaters.
A great feature of tankless water heaters is that they never run out of hot water — assuming the water heating capacity large enough to supply the needed hot water demands. They also don’t have stand-by losses. Because hot water isn’t stored in a tank, there is no heat loss when the water heater isn’t operating (though there will be some losses through the pipes during use).
A 2008 Consumer Reports article reported that gas-fired tankless water heaters used about 22% less energy than their storage-type counterparts. A 2010 study by the Center for Energy and Environment in Minnesota found that gas-fired tankless water heaters save an average of 36% over storage water heaters. So far, so good.

The size of heating elements

A key advantage of storage water heaters is that the heating element(s) can be fairly small. Because a significant volume of water is stored and because the tank remains stratified as hot water is drawn off, a properly sized storage-type water heater can provide a family’s hot water needs without requiring a very large flow of gas or electricity to heat the water.
Most gas-fired storage-type water heaters have relatively small burners, typically 30,000 to 50,000 Btu/hour (not much larger than the larger burner on a gas range). This means that a half-inch-diameter gas line is usually adequate to supply the water heater. It also means that the air intake (supply of combustion air) can be fairly modest in size.
Gas-fired tankless water heaters, on the other hand, often have much larger burners. A typical whole-house model, sized to allow two showers to be used at the same time or for someone to shower while the clothes washer or dishwasher is operating, will have a burner producing as much as 180,000 Btu/hour; the largest tankless water heaters have burners over 300,000 Btu/hour. Supplying the natural gas or propane to such a large burner requires a larger gas-supply line (typically 3/4-inch) than needed for storage water heaters — not an insignificant consideration.
Along with the large gas line, these tankless water heaters require a lot of combustion air. A small, 125,000 Btu/hour model operated at full capacity requires about 30 cubic feet per minute (cfm) of air for complete combustion, and a large, 180,000 Btu/hour model requires up to 45 cfm of air at full capacity. Such large airflow requirements can limit the options for placement.

Bigger challenges with electric tankless water heaters

An electric tankless water heater large enough to serve a whole house requires a huge current draw. A Seisco Model RA-28 that supplies 2.5 gallons per minute at a 76°F temperature rise draws as much as 116 amps at 240 volts! Most homes have only 200-amp service, and the multiple breakers and wiring required for such large current flows are expensive.
For utility companies, the idea of a lot of customers switching to electric tankless water heaters is downright scary, since hot water loads typically fall during periods of peak morning and early-evening power consumption. Utility companies are required to have capacity available for whatever the demand is, and if a lot of electric tankless water heaters were installed in a service district that would result in a significant increase in those peaks.

Flow rates

Some tankless water heaters have a minimium flow rate as high as 0.5 or 0.6 gallons per minute, meaning that at lower flow rates they won't come on. This can be a problem with low-flow plumbing fixtures, such as bathroom faucets.
Fortunately, manufacturers are responding to this concern. The Rheem H95 condensing tankless water heater pictured with this blog, for example, has a minimum flow rate of 0.26 gpm, the lowest I've seen — though the minimum "activation rate" is somewhat higher at 0.4 gpm.

Higher cost for tankless water heaters

While tankless water heaters save energy compared with storage water heaters, that doesn’t mean they are cost-effective. Both the Consumer Reports and Minnesota study mentioned above reported that the significantly higher cost of tankless water heaters resulted in payback periods longer than the expected lifetimes of the water heaters. Consumer Reports found the cost of tankless models to range from $800 to $1,150 plus about $1,200 for installation, compared with $300 to $480 for storage water heaters and $300 for installation.
The Minnesota study reported a 20- to 40-year payback for the tankless water heaters.
With certain usage patterns, though, the numbers could change. In a vacation home that is only used for an occasional weekend, the standby losses can be a huge percent of the total energy use for water heating, and a tankless model might make more sense. Or, in a commercial building in which a lavatory faucet is far away from the water heater and the hot water demand is very low, a small point-of-use tankless water heater may make sense — even an electric model.

Increased maintenance

On top of the questionable economics, tankless water heaters have significantly greater maintenance requirements than storage models.
Models designed for outdoor installation (where supplying combustion air is not a problem) include sophisticated freeze-protection systems. In places with hard water, scale build-up is a significant problem. If the hardness is above 11 grains per hour, experts recommend installing a water softener, according to Consumer Reports, and special provisions may be needed during installation to allow periodic flushing the heat exchanger coils with a vinegar solution.

The bottom line

The bottom line is that tankless water heaters simply don’t make sense for most whole-house applications. There are exceptions, as noted above, but for the vast majority of residential applications, storage water heaters make more sense.

Alex is founder of BuildingGreen, Inc. and executive editor of Environmental Building News. He also recently created the Resilient Design Institute.

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Do You Need to Upgrade Your Ventilation?

The average family produces 10 to 50 litres of moisture a day from cooking, bathing, washing dishes and other activities. A house that doesn't breathe can trap this moisture and develop humidity damage and mold issues. In addition, without adequate ventilation, carbon monoxide can collect in your home.

 

 

Affordability

Upgrading your ventilation could be as simple as replacing your bathroom fan and following some guidelines for good air circulation practices.

Cost savings

While mechanical ventilation does require energy, it is likely to save you money down the road. A poorly ventilated house is prone to rot and the occupants are more likely to suffer from allergies and other respiratory ailments. In addition, it takes more energy to heat wet air.

Health & comfort

For a healthy and comfortable indoor environment, air needs to circulate throughout the living space and be exchanged with fresh outside air. Proper ventilation can reduce mold, lessen the risk of carbon monoxide build-up and allow for energy-efficient air circulation.

Environmental considerations

Use a timer or dehumidistat with your fan to maximize energy efficiency by turning the fan on when it needs to be, but off when it doesn't.

What you need to know Efficient air exchange is best achieved through controlled mechanical ventilation. There are simple and effective ways to ensure you and your house breathe easily. Invest in new range and bathroom fans if yours are old. New fans are far more efficient – and much quieter! Ensure all fans vent outside your house, not into your attic or exterior walls. Have an electrician install a dehumidistat in your bathroom. These devices can be set to automatically turn the fan on when moisture levels get high. A great and fairly inexpensive way to ventilate your home is to invest in a bathroom fan with a timer and variable fan settings. You can set the fan to go on for a few hours a day when ventilation needs are high, like during the shoulder seasons when outside and inside air are similar in temperature. If you use your bathroom fan as your home exhaust, undercut the bathroom door to ensure that air can flow through from the rest of the house. A Heat Recovery Ventilator (HRV) is a great upgrade to a ventilation system. HRVs use heat from exhausted air to preheat incoming fresh air, making your ventilation far more energy efficient. In many homes, you can retrofit a heat recovery ventilator fairly easily. Ask your electrician or home energy auditor if this would be a good product for you. Natural Resources Canada provides some good information on heat recovery ventilators and an introduction to mechanical ventilation in general. If you are installing a new heating system, ensure it includes ventilation as well. Many new systems efficiently cover all your climate control needs. The Canadian Mortgage and Housing Corporation (CMHC) website has an informative section on Indoor Air Quality issues. FAQ Can I just open a window to circulate fresh air? Mechanical ventilation is far more efficient than opening windows and doors, and works well in all seasons. In fact, year-round energy use in more temperate parts of B.C. is often the same as that in colder places because of people opening windows and doors for fresh air in the shoulder seasons and then having to heat their space back up in the evenings. Our house is drafty, would that provide enough air circulation? Drafts are not a healthy or efficient form of ventilation. The air exchange can't be controlled and they are strongest when the difference between the inside and outside air is high. That means on cold nights, you are likely to feel a cold breeze coming into your warm house. Cold drafts can make rooms feel colder than it is and lead to inefficient heating and discomfort. During the shoulder seasons, when indoor and outside temperatures are more similar, you are likely to get very little air exchange.

 Source: BC Hydro
Brought to you by: House Smart Home Improvements 
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4 REASONS THIS SEASON TO SAVE MONEY ON NEW HOME WINDOWS!

Thinking of having new windows installed? Here are 4 Reasons not to wait!

1) Right now, until December 2012, House Smart Home Improvements will Pay the HST on your new windows! (Please call for details: 604-585-2020) 

2) Live Smart BC is paying you back 60 dollars for each window you have installed, but it all ends March 2013. There are 7000 dollars in grants available. Your House Smart Representative will provide you with all the details.

3) You probably already know how new windows will stop the drafts and cut down on your heating bill, saving you money now, and over time.

4) When you keep the heat inside your home and not going out of your windows, you conserve energy do your part to reduce your carbon footprint for future generations. Now there is something you can feel good about!

  Stop Throwing Money out the Window!

There has never been a better time to consider new windows for your home.  Enjoy the comfortable feeling of a draft-free home this winter. Call today for your Free No Obligation In-Home Estimate from House Smart Home Improvements: 604-585-2020.

15 Great Energy Saving Tips!

Here are 15 tips to help you save energy, save money and do  your part for the environment.

Try these easy, low-cost or no-cost energy saving tips:

Furnace
		1) Keep your furnace clean, lubricated and properly adjusted with annual maintenance. If your furnace is working at peak efficiency it will use less energy and cost less to operate.
		2) Clean or replace the filter every 1-2 months - a dirty filter reduces the airflow and forces the furnace to run longer to heat your home. 3) Consider purchasing a new ENERGY STAR® high efficiency furnace. An average home can save up to $509 in natural gas and electrical costs annually when upgrading from a standard 60% efficiency natural gas furnace to a 95% efficiency furnace with a high efficiency variable speed motor. House Smart Home Improvements claims that they can install a 96% efficiency furnace, and it comes with a 10 year parts and labor warranty as well. After government grants, you can have this installed for $2695. Contact House Smart Home Improvements for details: 604-585-2020  To stay on top of all of House Smart Home Improvement deals, LIKE their page on Facebook.           Thermostat 4) Lower your thermostat by 4 - 5 degrees Celsius (7 - 9 degrees Fahrenheit) while you're sleeping at night and when no one is at home. 5) Install a programmable thermostat. You can save 2% on your heating bill for every 1 degree C you turn down your thermostat. With a programmable thermostat to consistently lower your heat when you don’t need it, you could save up to $54 a year! House Smart Home Improvements installs these for you: 604-585-2020             Laundry 6) Switch to cold when doing your laundry. 85 – 90% of the energy used to wash your clothes is used to heat the water. By turning the dial to cold on your washing machine, you help the environment, save energy, and save money. 7) Wash full loads. 8) Choose a front loading washing machine. Not only does a front loading washing machine save water, it saves energy as well. It uses about 40% less water and about 50% less energy.     Weather-stripping 9) Weather-stripping provides a barrier between the fixed and movable sections of doors and windows. Apply weather-stripping to operable windows, exterior doors, garage doors, and doors that lead to the attic. 10) Apply a sealant or caulk around windows, doorframes, sills and joints. On a windy day feel for leaks or use a couple of incense sticks to help identify leaks around windows, electrical outlets, vents and exterior doors. As well look for spider webs - if there is a web there is a draft. The materials you need to seal the gaps are inexpensive ... More about draft proofing from House Smart Home Improvements. Windows 11) Cover your windows with plastic to conserve energy this winter. 12) Even better, have energy-star vinyl replacement windows put in by the experienced professionals at House Smart Home Improvements. Ask about the government grants available for this.  Basement 13) If you have an unfinished basement or crawlspace, check for leaks by looking for spider webs. If there is a web, there is a draft. A large amount of heat is also lost from an un-insulated basement. 14) Add insulation to basement walls. Visit House Smart Home Improvements for more information on insulation.  Drapes & Blinds 15) On sunny days, open south facing drapes and let the sun in, a natural source of heat. If you have large windows that don't receive direct sun, keep the drapes closed.

Act Now - Live Smart BC Efficiency Incentive Program will Close March 31, 2013

Tens of thousands of British Columbians are saving energy and money because of their participation in the LiveSmart BC: Efficiency Incentive Program. And even better they are also lowering their carbon footprint!

You can join your neighbours across B.C. who are saving money and reducing energy use by accessing these incentives.

During your Free In-Home Consultation from House Smart Home Improvements, you will learn about all the incentives that are available to you.

But act fast, because the current program will end March 31, 2013!

TAKING THE NECESSARY STEPS: Choose your contractor wisely. House Smart Home Improvements have years of experience and can help you with multiple home energy-saving renovations such as replacement energy-smart windows, doors, insulation, furnaces and heat pumps. They also provide initial Free In-home Consultations. During your Free In-Home Consultation with House Smart Home Improvements, one of our experienced professionals can help you decide what renovations would best upgrade your home while staying inside your budget. He / She will also put you in touch with a Certified Energy Advisor. After you have made energy efficiency improvements to your home, you will complete a second assessment within 18 months of your first assessment  (or by March 31, 2013, whichever comes first). The energy advisor will submit your application giving you access to applicable LiveSmart BC incentives. Your home will also receive an upgraded EnerGuide for Houses rating. Expect a cheque in the mail!

Please note:
There are specific requirements that must be met in order to be eligible for incentives. Please read about the eligible improvements carefully. If you are unclear on requirements, contact  House Smart Home Improvements before purchasing or installing any equipment.

This information brought to you by House Smart Home Improvements via the Live Smart BC website.