Tankless Hot Water Systems

Tankless Hot Water Systems

Tankless (On-demand) Water Heaters vs Hot Water Tanks

With energy efficiency becoming more important every day, we all need better and newer methods of saving energy and hopefully money as well.

Tankless, instantaneous, or on-demand hot water is gaining in popularity.  Energy efficiency is reported to be in the 95-97% efficient range for condensing units.  Tankless heaters only heat the water when you turn on the tap, they run quietly, and CO2 emissions are reduced by 900 to a 1000 lbs per household on average.

The question for you is whether it’s right for you. You need to know what you’re getting into. Tankless may work great for some families, but it’s not for everybody.

No Tanks

The main point to understand is that there is no storage tank and so there’s no hot water storage at all.

With a tankless system, when you turn on a hot water tap, this is what happens:

  • Opening the faucet lets water  flow inside the pipe and out of the faucet.
  • A flow sensor within the tankless system detects this flow within a few seconds.
  • Once flow is detected, the computer activates the unit, starting up the burners and exhaust fan
  • The cold water goes through these burners in  to a heat exchanger (a series of small water tubes or channels) quickly heating the water to the set temperature (also continually monitored by the computer).
  • When heated to the set temperature, the hot water is sent on its way to the open faucet.
  • When the faucet is closed, the flow sensor recognizes the water flow has stopped and notifies the computer , which then shuts down the burner and goes dormant until the next call for hot water by an open hot water tap.
This flow is also important when considering a tankless unit’s practical use. Various tankless models are designed with various levels of maximum flow. This flow is measured in GPM (gallons per minute) for a set temperature rise. Many tankless units considered to be multi-bathroom use capable, can produce 9 GPM of heated water with a 35 degree fahrenheit temperature rise. This means that if the cold water entering the house is 40 degrees fahrenheit, the unit is capable of “instantly” heating it to 75 degrees at 9 GPM of flow. This same unit would also be rated at approximately 7 GPM with a 45 degree fahrenheit temperature rise, so it can keep up with a solid 85 degrees (about the temperature of a swimming pool) at 7 gallons per minute of flow.
Typical flow for:GPM
(gallons per minute)
Wash machine3
Shower head2.5
Kitchen faucet2.2
Bathroom faucet1.5

Most hot showers run about 105 degrees so the tankless unit will need to raise the water temperature 65 degrees. To accomplish this temperature rise, we can estimate the flow rate to be around 3½ to 4 GPM. With a shower head that only allows 2½ GPM of flow, we have about 1 ½ to 2 GPM of room.   Fingers crossed that no-one turns on a dishwasher or wash machine!

An older hot water tank, works like this:

  • When you turn on a hot water tap, water flows from your hot water tank (that is already filled with hot water) to the faucet.
  • There are generally no computers, no fans, no waiting for burners to come on to heat,  and no flow reduction based on temperature demand. Its full flow all the way at 140 degrees.  Some higher efficient tanks  do have venting fans and some have small valve computers but very simplistic in their operation.
  • A standard hot water tank can easily handle simultaneous usage. No need to turn off the wash machine or dishwasher when someone is in the shower. Flow limitations for a standard hot water tank system is dependent upon the waterline sizing, not the water heating capability.

Energy Requirements

Tankless heaters have no time to gradually heat the water, it needs to heat the water fast right now.  A typical gas tankless heater runs at a huge 199,000 BTU compared to a tank system which could run at 50,000 BTU. Thankfully, it only fires on demand, but when the demand is there it FIRES! If you have an hour long shower, its firing for an hour long. A typical hot water tank relies on its storage (usually 40 to 50 gallons) and an extended recovery time (30 to 40 minute range). In my previous house I installed a quick recovery 50 gallon hot water tank, that recovered quickly enough that even when we had lots of guests staying over, it easily kept our water hot. It was a 50,000 BTU tank.

BTU (British Thermal Unit)
One British Thermal Unit is the amount of energy it takes to heat 1 pound of water 1 degree Fahrenheit. With appliances, the BTU value refers to BTUs per hour.Lighting an ordinary match and letting it burn its length radiates about 1 BTU of energy.Imagine lighting 199,000 matches and you can see the energy released by a tankless water heater in an hour!

Energy Efficiency

Most tankless units are energy efficient within the unit themselves.  With higher end condensing units upwards to 97% energy efficiency rating, you may be surprised that some natural gas hot water tanks have energy efficiency ratings as high as 95%. Some commercial hot water tanks are rated as high as 99.1% efficient.  You an touch a modern tank fully heated and feel nothing but cool metal due to high insulation factors.   Modern hot water tank heaters are much more efficient than they used to be.

No insulation on the hot water lines

A major cause of heating loss comes hot water lines in the house that aren’t insulated. If you have a tankless water heater with watering running through uninsulated water lines, it loses energy the whole way along the line until. This is why the water gradually gets warmer until its hot. The same is true for typical storage hot water tanks. The simple solution is to insulate as much of the visible hot water line as possible.

Cold Water Sandwich

People investigating tankless systems will hear the term “cold water sandwich”.  With a tankless system, let say your teenager just had a shower so the lines between the shower and the tankless heater are hot. When someone else now has a shower, there is immediate hot water because the lines are all full of hot water. But remember, with tankless systems, while the flow sensor is waiting for a ½ gallon of cold water to go through it before it starts heating, you’ve got a ½ gallon of cold water in the line coming towards you.

So what to do about this? We always, always put in a water storage tank to work in conjunction with a tankless heater. Anywhere from a 2 to 30 gallon electric works just fine for this. It acts as a buffer to ensure that any cold water is completely absorbed by the hot water tank. Also, the electric tank will be always be ready and waiting for you, full of hot water, so you truly get the instantaneous heat you’ve grown accustomed to. Instead of the electric tank having to heat up cold 40 degree water, it is fed only hot water from the tankless heater, making it more efficient. There are also hybrid hot water heaters that combine both tankless with a storage tank in one unit.

To be fair, many tankless water heaters now try to reduce the cold water sandwich effect using various methods. On of these methods is to measure the length of time between the last hot water usage and the current hot water request. If the time is short enough (a minute or two), the tankless unit will fire up within one or two seconds reducing the amount of cold water coming at you.

Some systems like various Navien models utilize an internal circulating pump.  It is installed in such a way that circulates the water back through the system and mixes it with some heated water. It can be a useful method of dealing with the temperature issue but it does affect the overall efficiency.  Still more efficient than the old systems.

Whatever method is used, if the cold water sandwich is still with us, and something you need to be aware of.

Final thoughts

The biggest plus that I can give to a tankless system is that is takes up less space. It hangs up very nicely on the wall. When installed correctly, it’s a clean looking unit. However, by the time you’ve also installed the “buffer” tank if needed, the space savings start to dwindle. When installed correctly, a tankless system can be as efficient as a high efficiency storage tank, but the installation price is certainly higher, and you end up having a water storage tank anyhow. Tankless is very trendy right now, and yes we do install them, but you might want to talk to us about high efficiency water storage tanks that will save your pocketbook as well as the environment. If your convinced a tankless system is right for your situation, get a price quote for installing a tankless hot water heater in your home.

Are you in need of help with your hot water tank? It might be time for a service call, or it could be damaged and has to be repaired or replaced. That’s where we come in!

At Airco Heating and Cooling Ltd., we are here to supply you with any of your hot water tank requirements within the Lower Mainland and Fraser Valley.

We service all makes and designs of tankless hot water heaters in Surrey, Langley, Delta, White Rock, and other areas, including:


And most other brands!

Energy Star Hot Water TanksEnergy Star Rated Tankless Hot water heaters in Surrey, and surrounding communities are common home appliances that frequently need repair work, service, or replacement.

While maintenance and repairs are typically unexpected, we will provide you with alternatives based upon any specific scenario. Our hot water system replacement costs are based on market requirements using high-quality materials and professional tradespeople in the Lower Mainland.

When it comes to hot water tank maintenance and upkeep, we believe that regular servicing is the very best policy. When considering a hot water tank, be proactive and get your system maintained and serviced on a regular basis. Most service warranties need you to service your devices a minimum of once a year.

At Airco Heating and Cooling Ltd., if we can not repair your hot water heater tank  or tankless heater or you are searching for something more energy efficient and reliable for your house, we will suggest and set up the best equipment for the task. Our estimates are detailed and complete. We jot down everything we plan to set up and do because so you know exactly what you are getting for your money.

Serving the Lower Mainland and Fraser Valley Communities of BC, including:

  • Surrey
  • Langley
  • Delta
  • White Rock
  • Cloverdale
  • Abbotsford
  • Maple Ridge
  • Pitt Meadows

If you need an on-demand tankless hot water heater in Surrey or you need one in Langley, Abbotsford, Delta, or White Rock, we are here to help.  You can trust that Airco Heating and Cooling Ltd. provides the best in well-thought and comprehensive out hot water tank system service, replacement, and repair service work to all members of our community. Contact us today!

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