Is a solar water heater the same as a tankless water heater?
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Solar water heaters are quite common here actually
Question by mattflorws: Is a solar water heater the same as a tankless water heater?
Are all tankless water heaters solar? Do the tankless water heaters or solar water heaters for the home really pay off?
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4 Responses to Is a solar water heater the same as a tankless water heater?
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two different animals
a tank less water heater is gas or electric……it only turns on when you open a hot water tap somewhere in the system….it senses water flowing, turns on the heating element and then turns off when the water flow stops.That way you aren’t keeping 25 or 40 gallons in the tank hot 24/7. ‘Cause there isn’t a tank. The whole unit is about the size of a large phone book or a small briefcase.
We put 75 of them into the condo I run and peoples electric bill dropped about 25%.
Generally the tank less heaters will raise the incoming water temperature about 25 to 40 degrees. They draw A LOT of current for the few minutes they are running.
A solar water heater is a long run of copper pipes inside a frame, with a glass or plastic cover……it’s about the size of, say, a large desk or a double bed and about 6 inches thick. You mount it somewhere that the sun can shine on it. Usually the roof but it could be at ground level. Water runs through the copper pipe and absorbs heat from the sun and then goes into the pipes in the house and to the taps.
An ideal set up would have the solar heater preheating the water before it goes to the tankless heater…should drop your hot water bill 25-40%, because in the summer a solar heater makes water hot enough to not need the boost from the tankless.
yankee_sailor
October 17, 2011 at 2:25 am
Yankee Sailer’s answer is perfect. Solar water heating can preheat water for an on-demand, tankless water heater, saving you over 75% of your water heating bill.
I just wanted to add that you need to make sure the tankless water heater used as a backup heater for solar water heating should be a modulating heater, able to sense that the water coming in to it is already hot, and turn down as needed. Some old ones sense water and turn on, regardless of how hot the water is, saving you nothing. Also, some brands will void their warranty if hot water is sent into it.
Bosch makes one that is designed for solar integration, http://www.boschhotwater.com/BoschHotWatercomHome/GasProducts/BoschModel1600PS/FeaturesandSpecs/tabid/1012/Default.aspx.
Here’s a link to solar water heating systems, so you can see the difference. http://www.altestore.com/store/Solar-Water-Heaters/Climate-freezes-Closed-Loop-Systems/Closed-Loop-Systems-for-1-4-People/Closed-Loop-PV-Powered-w-Tank/Indirect-w-80-Gal-Tank-64-SqFt-Collectors/p8142/
Amy
October 17, 2011 at 2:36 am
No.
you could use a solar water heater to preheat the water for a tankless water heater, but that would be buying 2 heaters to do one job. What a waste.
As to whether they pay off well that just depends on your time scale. Some reports say that it would take 80 years to repay the cost of buying the system, but if you had to buy a system anyway because the old one was worn out or it’s a new house then why not use solar ?
Don’t believe the marketing hype of companies trying to sell you these systems, claiming to recoup your money in one or two years.
lombardo_uk
October 17, 2011 at 3:17 am
They are quite the opposite in the way they work.
Tankless water heaters can be heated with oil, gas or electricity. They are sometimes called “on demand” systems and are additionally sometimes placed at point of use. A great deal of concentrated energy is used to rapidly heat water as it is flowing through a pipe to your shower or other end use. The advantage of tankless heaters is not having to spend money for the energy used to maintain the heat in a tank full of water. The equipment can cost the same or less than a tank style water heater. Depending upon your type of use they can save you some operating costs (that would otherwise be spent on heat lost from a tank of unused standing hot water.)
The energy from the sun is diffuse. It has to be collected over a large area or over a longer time and then concentrated to become useful. Solar water heaters should always be heating up a storage tank of water (concentrating and storing the heat energy) in order to keep the collector size to a minimum while providing hot water for nighttime and cloudy days. It makes the system most economical. The storage tank is usually larger than a a typical fuel powered hot water cylinder. These systems are initially more costly than conventional hot water systems however over the course of 3 to 5 years you should pay for your investment in fuel savings. The advantage of this system is that you pay nothing for operating costs: the fuel is free.1
Solar water heating systems are typically designed to handle about 80% of hot water usage. The balance requires a back up system. Instant hot water heaters could be used because the equipment is cheaper and there is some space savings. However a tank system will increase the total system storage capacity and will typically be super insulated.
Tank systems are better when there is a relatively constant demand for hot water. There can be less heat loss in heating the water when it is heated at a lower rate.
Breath on the Wind
October 17, 2011 at 3:58 am