Solar water heaters versus modern conventional water heaters

When does purchasing a solar water heater make sense?
By Boris Romanov

  There are many brands of solar water heaters on the market now. They are different in prices and in technical capabilities. The sun exposure varies within different regions also.
Therefore to calculate the payback periods of solar hot water heaters we have to take into account all these parameters.

The types of solar water heaters:
- Solar collector integrated into the storage tank;
- One, two or even three solar collector(s) with separated storage tank. These types of solar water heaters could be a "Glycol System/Non-toxic antifreeze systems" or "Drainback System";
- Solar water heaters based on solar air collectors.

  "Thermosyphon Solar Hot Water Systems are amongst the most affordable and simple to install of all Solar Hot Water Systems. SunMaxx Thermosyphon Systems are built around our revolutionary SunMaxx Evacuated Tubes, and feature an integrated Solar Hot Water Storage Tank that mounts directly to the top of the Solar Collector.
Available in 40 and 80 Gallon models, Thermosyphon Systems from Silicon Solar are a incredibly affordable and cost-effective investment - wherever you live."


To keep the exterior pipes from freezing a heating cable is installed between the cold water pipe and the hot water pipe in the insulated PVC covering that is outside of the house.
The cable is turned off and on according to the temperatures outside. The controller turns on the cable when the cold water pipe gets to 2°C and turns off when it reaches 6°C.
The electricity consumption of the heating cable with a controller in the winter is given below:
Running period: December 24th, 2009 - March 2nd, 2010, or 69 days.
Costs of the electricity consumption: 12 cents/day (in average), total: $8.28/winter (year).
Roughly, 1 kWh a day."
Note: This photo and comments are posted with permission of Globe Solar Energy Inc

Solar Water Heater Integrative Coiler 200 liters/20 tubes

Advertised, Unconfirmed price: $899.00

"Since 1992, SunEarth has teamed with Edward’s Solar Hot Water (now part of Rheem Australia), a world leader in the manufacture of stainless steel storage tanks and boilers, to market a packaged thermosiphon system under the brand name ‘SunSiphon’ in North America and the Pacific Basin. The SunEarth/Edward’s collaboration offers the best of two continents - the world’s finest thermosiphon storage tank and rugged, high performance SunEarth flat plate solar collectors. SunSiphon systems are available both with and without integrated heat exchangers for hard freeze and non-freeze climates, respectively."
"Thermosiphon systems have no moving parts and use no parasitic energy in their normal operation. The simplicity and long-term reliability of the SunSiphon thermosiphon system remains its principal selling feature.
If properly installed and maintained the SunSiphon glycol heat exchange system can safely be deployed in areas that experience annual hard freeze conditions. SRCC Rated Freeze Tolerance: 15°F for 18 hours."

"Traditional Drainback Systems use a pump to circulate water or glycol in the collector loop, which drops into a reservoir tank when the pump stops. They also use a differential controller to start the pump (or the pumps) and to route the water into the system. This process begins whenever the sensors attached to the collector detect useful sunlight available (which happens when the temperature in the collector is higher than the temperature of the water at the bottom of the storage tank)"

New OG300 Certified Simple Drainback Pre Packaged Kits with Flat Plate Collectors

"The HelioMaxx SDB system was designed to bring the simplicity of drainback systems together with some of the better characteristics of pressurized systems to create the easiest installation on the market. Our newly released 3rd Generation System is even more efficient in its design, components and function. The Kit has also been OG-300 Certified by the SRCC.

The StorMaxx SDB Drainback/DHW Tanks are made with extremely durable materials with a high tech titanium steel/porcelain enamel bond that is expected to last 15 years or more. Our spirally augmented copper coils allow extremely efficient heat exchange within the tanks. Our outer jacket made from painted alloy steel provides a very clean look to the system. We use polyurethane insulation for maximum heat preservation."

More details are Here

Note: The annual average performances for the one TitanPowerPlus-SU2 Solar Collector is about 5,986,000 BTUs in warm climate and about 3,522,250 BTUs in cold climate.

New OG300 Certified Simple Drainback Pre Packaged Kits with Evacuated Tube Collectors

More details are Here

Note: The annual average performances for the one ThermoPower-VHP20 Solar Collector is about 7,446,000 BTUs in warm climate and about 5,803,500 BTUs in cold climate.

"SunMaxx Empire Kits are a complete solar thermal system in a kit. Kits come in either a flat plate (TitanPower Plus-SU2) or evacuated tube (ThermoPower VHP) fashion. Kits also include stainless steel line set, a UniMaxx Plus pump station, the StorMaxx SE glass lined storage tank and all the fittings necessary to connect all of these components.

The Empire kits were designed to preheat your existing hot water system or completely replace your existing one. These Empire kits are also OG-100 certified! We have designed complete and comprehensive systems that can replace your existing electric hot water heater and save you up to 75% of you energy consumption for years to come!"

More kits are Here

SolarSheat Hot Water System
Sale price: Sale $7,399.99

"The SolarSheat® Hot Water System is an innovative dual mode solar air space heating system for the winter and a supplemental solar domestic hot water system in the summer. The SolarSheat uses household water and does not require glycol or other additives. The system uses automatic dampers and can switch between heating and hot water modes quickly."


An additional, one of the most efficient design is here: Integrated system: hot water and home heating

My calculation of payback period for Integrated Tank Solar Collectors/Thermosyphon Solar Hot Water Systems in comparison with propane and natural gas

Initial data:
- The annual average performances for one collector with 30 tubes is roughly 11,242,000 BTUs in warm climate and 8,760,000 BTUs in cold climate.
- One gallon of propane can produce approximately 91,600 BTUs.
- One cubic foot of natural gas can produce approximately 1000 BTUs.
- One cubic meter/metre of natural gas can produce approximately 36000 BTUs.
- One cubic meter/metre is equivalent to 35.3 cubic feet.
- August 2011 price of propane/LPG (in my area):$3.25/per gallon. Updated Propane prices are here
- 2010 USA national annual average residential natural gas price was $12 per thousand cubic feet (Mcf).
- 2010 Canada national annual average residential natural gas price was 25 cents for one cubic meter

So, 123 gallons of propane (11,242,000 BTUs/91,600 BTUs per gallon) could be offset in warm climate
and 96 gallons of propane (8,760,000 BTUs/91,600 BTUs per gallon) could be offset in cold climate.
That leads to savings of about $399.75 (123 gal. x $3,25) in warm climate
and $312(96 gal. x $3,25) in cold climate respectively.

Or 11,242 cubic feet of natural gas (11,242,000 BTUs/1000 BTUs per cubic foot) could be offset in warm climate
and 8,760 cubic feet of natural gas (8,760,000 BTUs/1000 BTUs per cubic feet) could be offset in cold climate.
That leads to annual savings of about $135 (11,242/1000 x $12) in warm climate
and respectively leads to savings of about $105 (8,760/1000 x $12) in cold climate

To summarize, for areas where natural gas is used for water heating, and if you will spend around $4,000 for the simplest solar hot water system, the payback period (investment return period) is more than 17 years EVEN with application of federal tax credit and other state (province)/utility rebates in the warm climate and more than 20 years in the cold climate.

In Canada the natural gas is less expansive. Therefore the real savings are less attractive
In real life, we should further increase these numbers because of the losses that occur in solar storage tanks and transfer pipes.
The result will be even worse for solar collectors with 25 or 20 tubes.

In some cases when "... a family of four spends $455 per year for hot water. The family installs a $4,500 solar water heating system that reduces their annual water heating bills by 65%. It will take 15 years for the systems to pay for itself. Adding in the federal tax credit of 30%, cuts the system cost to $3,150. This will reduce your payback to 10.5 years."

"Before purchasing a solar water heating system, you can estimate its annual operating cost and compare it with other more and/or less efficient systems. This will help you determine the energy savings and payback period of investing in a more energy-efficient system, which will probably have a higher purchase price."
More details are here: Estimating a Solar Water Heater System's Cost

Calculation of payback period for areas where electricity is used for water heating:
According to the US Department of Energy national annual average of electricity costs for a standard 50 gallon electric water heater is $520.
New installed solar hot waters systems with two collectors and 80 gallon tank initially cost $8,000 or more.
After receiving all tax credits, rebates and government incentives, the customer could get the cost of equipment reduced by up to 50% or a discount of approximately 40% from the total cost.
Therefore this investment in the amount of $4,800 (60% of initial cost of system) could save roughly $520 annually.
To calculate the potential reimbursement period in years (without additional maintenance and operational costs), we have to divide the cost of the system by the amount of annual savings. In other words, the investment return period is over 9 years ($4,800 / $520 = 9.2 years).
At the end of this period, the system would be worth its "residual value" and still could produce hot water for FREE!

I think the most reliable and less expensive combination is a SanMaxx-30 solar collector with an AMTROL BoilerMate.

Here you can see price info.

Maine disadvantages of Solar Collectors:
- difficulties with snow/ice removal especially for the roof installation..,
- overheating if collector is not in use. That leads to increase in the number of unused BTUs!...
- additional cost of electricity to heat pipes in cold weather in order to avoid their frizzing.
- additional cost of equipments for drainback systems in cold weather in order to avoid their frizzing.
- an efficiency almost all flat plate solar collectors is very low during cloudy days, especially in the cold climate!

Electric Heat Pump Water Heaters

"The Heat Pump Water Heater is an integrated system that utilizes heat pump technology to provide a more efficient way to heat water with electricity. Similar to your home air conditioner in reverse, the Heat Pump Water Heater extracts heat from the surrounding air and transfers the heat to the water in the tank.
This is a very efficient means of heating water, and yields a by-product of cooler, dehumidified air. More storage capacity allows the water heater to operate in the most efficient mode and generate greater savings compared to smaller capacity heat pump models.

All heat pump water heater have another great benefit because they act as huge dehumidifiers. As they remove the heat from the room they also remove the humidity, turn in to water for it to go into a near by drain. The condensate water can also be pumped into a drain, laundry drain, sum pump, or slop sink with an additional condensate pump."

GE GeoSpring 50-Gallon 10-Year Hybrid Heat Pump Water Heater ENERGY STAR - $950

I bought it from the Interstate Appliance.
No Sale Tax and FREE shipping!

This modern and energy efficient water heater is a real bargain. It costs less than the lowest price of a regular 50 gallon electric water heater ($950 - $400 rebate - $300 Tax credit).

In fact, I think it's nearly impossible to buy or to build a reliable (regardless of weather condition) solar water heater for the price of $250.

Limited 10-year warranty provides peace-of-mind and dependability.

Call Joe Kieffer at (720) 881- 8301 for the best price. You can save a lot of money in comparison with Lowes or Sears.

"GE first to announce water heaters that will meet new DOE ENERGY STAR® standards
In the wake of the Department of Energy’s announcement today that creates ENERGY STAR® criteria for residential water heaters, GE is proud to introduce two innovative products that will meet the new requirements.
The GE Hybrid Electric Water Heater and GE Tankless Gas Water Heater, both currently in development, represent the latest in a series of GE appliances designed to help energy efficiency in the home.

The DOE’s new ENERGY STAR program, for heat pump water heaters and tankless water heaters, is the result of many months of analysis of technologies, market opportunities and consumer interest.
GE was one of the key participants in the criteria-development process and urged the DOE to adopt aggressive standards for high-efficiency ENERGY STAR water heaters.
ENERGY STAR standards are important because second only to residential heating and cooling, home water heating is number one in residential energy consumption. Even as homes are designed to be more energy-efficient, the percentage of energy used in water heating is still a predominant factor.

The GE Hybrid Electric Water Heater combines energy-saving heating technology with traditional electric heating systems used in most standard water heaters on the market today without sacrificing the amount of hot water it can deliver.
This hybrid technology is designed to absorb heat in ambient air and transfer it into the water. Since it requires much less energy to absorb and transfer heat than it does to generate it - as a standard electric water heater would - the GE Hybrid Electric Water Heater provides the same amount of hot water while using less energy.
The GE Hybrid Electric Water Heater features a user-friendly electronic control system that offers both simplicity and flexibility, giving consumers as much or as little control of operating modes as they like: Set the thermostat and forget it or easily change the desired water temperature to maximize energy benefits.
The GE Hybrid Electric Water Heater is designed for easy installation because it uses the existing water and electrical connections and occupies the same footprint as a traditional tank water heater, making it perfect for new construction or a replacement upgrade

The GE GeoSpring Hybrid Water Heater is America’s most efficient 50-gallon water heater, using 62% less energy and saving $325* a year on utility bills.

The investment return period is less than 1.5 years with application of federal tax credit and other state and local utility rebates." You can get more details from GE Here.

Useful link - GE Heat Pump Water Heater Report

Whirlpool Heat Pump Water Heater

"2.3 EF: Saves the home owner significant money. Standard electric water heaters are .87 to .95 EF. Less than half the cost to operate compared to a standard electric model (average of $540 versus $201 for the Heat Pump Water Heater).

Pay back in 3 years, or quicker with state and local rebates.

Extra Capacity To Store The "Cheap" Hot Water: Both the 80 and 60 gallon capacity models can store more energy created from the heat pump technology (versus from the electric element) and yield greater savings."

More details are Here

Tankless Gas Water Heater
Condensing gas water heaters are most efficient and reliable among gas water heaters.
Navien has created high capacity condensing tankless water heater models that have an efficiency of 98%.
Rheem, Rinnai/GE, Bosch, Noritz and Takagi make condensing water heaters that are not too far behind.
Some brands already have a very good reputation. For example, "Rinnai is the 2010 Builders' Brand Leader as chosen by home builders in Builder Magazine. The Alliance to Save Energy awarded Rinnai their prestigious Super Nova Star Award for energy efficiency and chose Rinnai as The Best Tankless Whole-House Water Heater...
Energy savings with a tankless water heater typically result in a payback within just a few years for a family of four, making a tankless water heater a better long-term investment." More details are Here

To calculate the potential reimbursement period in years you have to divide the cost of your installed heater (after all credits and rebates) by the amount of annual savings.
For example, roughly the investment return period is about 4 years ($1000 / $250 =4) years) for natural gas or less that 3 years ($1000 / 400 = 2.5) for LP.
With the Tankless Water Heater Energy Savings Calculator you can calculate your specific savings amount.

GE Tankless Gas Water Heater Eliminates the Hassles
"GE also has a solution for consumers who use gas water-heating systems. The new GE Tankless Gas Water Heater provides hot water while using less energy than a standard-tank gas water heater because it only activates when you need hot water and it immediately de-activates when you turn off the water. This demand-activated technology allows users to receive a continuous supply of hot water. Demand-activated technology also translates into significant energy savings. A GE tankless gas water heater could help homeowners save up to 25 percent annually on water heating costs compared to the operating costs of a standard 40-gallon-tank gas water heater.
The GE Tankless Gas Water Heater is offered in two sizes (7.5-gallon-per-minute flow and 9.4-gallon-per-minute flow), indoor and outdoor. The 7.5-gallon-per-minute flow is available for natural gas; the 9.4-gallon-per-minute flow is available for natural gas or LP gas."

Rinnai RC98HPi 96% Gas Condensing Tankless Water Heater 9.8 GPM - $1,265 and Up

"Rinnai’s latest tankless addition incorporates condensing technology to deliver more efficiency than ever before. Available in four models, suitable for mid- to large-sized homes, Rinnai’s new Condensing Tankless Water Heaters offer all the same benefits builders and homeowners have come to expect from Rinnai. Never run out of hot water again, and enjoy the space savings, convenience, ease of installation and peace of mind for which Rinnai is famous. The efficiency of condensing technology Rinnai’s unique condensing design incorporates two innovative heat exchangers to achieve optimum heating value from every cubic foot of natural gas or propane. The stainless steel system recaptures residual heat from flue gases to pre-heat incoming ground water, which then circulates to the primary copper heat exchanger."
"Delivering up to 97% thermal efficiency, Rinnai’s tankless condensing units are ideal for residential and commercial applications and can be banked for even greater capacity. The Rinnai Tankless Water Heater brand offers you high efficiency, reliability and greater service with technical support."

EcoSmart 11 Kw Tankless Water Heater - just for $206.55 from

"Lifetime warranty
Save up to 60-percent on your water heating cost with an ECOSMART electric tankless water heater
Never run out of hot water with an ECOSMART tankless water heater
Patented Self Modulating Technology and design
ECOSMART tankless water heaters are 99.8-percent energy efficient"

"...WOW, My first electricity bill came and I save 33 dollars compared to the previous month. Nothing in my house has changed from previous billing cycle to this current cycle. At this pace the investment will pay for itself in like 6 months that its VERY IMPRESSIVE!!!"
Review from:

"Navien Condensing 98% Tankless Water Heaters" - $1,098 (150K BTU) and Up.

"Natural Gas With Navien Condensing 98 percent, you get the best of both worlds: the Best Value and "Ultra Condensing Efficiency", which offers substantial savings and contributes to a green-friendly environment."

"Because this product boasts the industry's highest efficiency, rating (98%) means customers can cash in on low annual operating costs as well as receive the best payback, compared with conventional tankless or tank-type water heaters.
Navien's Condensing 98% Tankless also enjoys the highest gallons-per-minute (GPM) when comparing input BTUs."
"We here at Navien America pride ourselves on manufacturing the most cost-efficient Water Heater available. Our built-in hot water recirculation system recirculates hot water that would otherwise be lost, thus, creating a method that lowers the cost of our customer's water bills each month.
Navien's state-of-the-art technology means our product has a longer life span and lower operating costs than other water heaters, compounding customer savings. This, coupled with Navien's space-saving wall-mount design, which frees up your home's real estate space, only increases the money customers will save. And, Navien's 15-year warranty is the best in the industry - think of it as an added bonus!
Navien America is an official Energy Star partner for tankless water heater." More details are Here

Bosch Space Heating & DHW Greenstar Combi 100

""Combi" (combination) unit with space heating and integrated water heating in one highly efficient, compact unit.
With special insulation to ensure ultra quiet operation and the exclusive keypad safety lock feature to prevent unwanted tampering with heating controls, this unit is the ideal "green" upgrade for detached & terraced houses and is also suitable for apartments.
Aluminum-Silicon heat exchanger delivers high efficiency - 98.5% with low temperature applications (96.0% AFUE)"
More details are Here


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