Everyone that has looked into the details is impressed with the relative economic value of a solar water heating system compared with any other renewable energy source. Even if a potential customer is impressed with the economics of solar heating it doesn’t mean that they can necessarily pay for it. Many potential customers don’t have access to the cash so discussions of tax incentives and rebates fall on deaf ears if they don’t have the money up front.

One of the missing pieces in the solar heating equation has been the financing. This has been a hurdle at both the residential and commercial level. I am aware of a number of banks that offer different systems but one that came to mind recently that I thought had some merit was www.sameascashloans.com . The premise is that you can offer your customers a solar system and they can defer the first payment for anywhere between 3, 6, 12, or 18 months. This way the customer doesn’t have to be cash out of pocket until they are realizing the tax savings.

On the commercial side it is a little more like standard financing but the availability of financing makes this a strong option for growing your solar heating business.

In the last blog I mentioned calibrating the customers expectations by providing them with a simulation showing what they can expect from their system. Occasionally, a customer will not realize the savings they should and they expect you to fix it. Under the right circumstances it is possible to install a solar heating system and see only a small fraction of the savings that should be delivered…

One such situation is when the customer uses a solar tank to pre-feed an indirect gas or oil fired tank that operates as the back-up to their system. When using a boiler fed tank as the back-up, it is possible to intermittently not achieve the desired temperatures in the indirect tank thus requiring the boiler to cycle on. If this is in the summer time when the boiler is only used to service hot water (and not heat the house) this means that all of the losses and waste associated with starting up and shutting the boiler down is still there. How can we eliminate (or at least minimize) the intermittent cycling of the boiler when the solar tank is already hot?

One way to reduce the boiler cycling is to tie the solar tank together with the indirect tank in such a way that any excess heat in the solar tank is shared with the back-up tank thereby reducing the demand on the boiler. This can be accomplished simply with an extra connection between the tanks, a pump, a check valve, and a differential control. When the solar heated tank exceeds the temperature in the back-up (indirect) tank the circulator turns on and causes the two tanks to be mixed together in such a way that the heated solar water moves into the back-up tank. By tying the tanks together in this manner you have accomplished several things including: reduced the firing of your boiler increased the overall efficiency of the solar collectors (by keeping the tanks at a lower overall temperature) significantly reduced the customers overall energy bill in the summer time. made the solar system more robust and resistant to overheating (glycol systems)

While this technique will not hurt in any way it’s greatest benefit will be seen during the summer when the solar system is capable of producing the extra energy. It is possible to totally eliminate the customer fuel oil usage in the summertime with this scenario.

Click here for a sample drawing

As the solar water heating business expands to the traditional trades (plumbing and HVAC) we get questions about system payback more and more.  The contractors want to understand that the systems they install will rapidly pay for themselves.  While this is an excellent question it comes laced with many pitfalls.

We can quickly go down the road of answering this question for our own satisfaction although I don’t recommend it in general.  According to “More evidence of Rational Market Values for Home Energy Efficiency” by the Appraisal Journal a home will increase in value $20 for every $1 reduction in annual energy bill.  An average solar water heating system will save a family of 4 approximately $400 per year on their energy bill.  That would mean that if a homeowner installs a system they she see an appreciation in the value of their home of $8,000.  Interestingly, that is also about the national average installed cost of a 64 ft^2 80 gallon tank freeze protected system.  You add to that the current tax incentives which include as a minimum 30% tax credit from the federal government and you now have a system that costs less than it adds in value to your home.  With this stunning fact it would seem that every homeowner that is about to sell there home should add a system simply by the pure economics.  I make the last statement a little tongue in cheek because I understand that some homeowners are concerned about the aesthetics of an installation (I am sure to discuss that later in a future post).

When it comes down to it, the economics of solar water heating are such that a homeowner get shift there assets from their bank to their home and in return get a huge chunk of cash from the government and start saving money immediately on their utility bills.  This should be a no-brainer economically.  Although the logic is clear I don’t recommend sharing this with those that question the value of solar water heating (or more likely solar energy in general).  People’s prejudices, party affiliations and biases are such that rare is the person that will listen to logic.  I would recommend to focus the selling of systems to people that are already convinced of the value of energy efficiency they can be seen all around us.  They are the people that drive hybrids, purchase high SEER air conditioning, bicycle to work, use compact fluorescent lamps, or install programmable thermostats.  The people that are ready are all around us so we need to stop focusing on the people that won’t be convinced no matter what the logic.

Another article that might be interesting is: http://www.pmmag.com/Articles/Column/BNP_GUID_9-5-2006_A_10000000000000620715

(the bottom of my tank)

Contractor leaves the job site satisfied that they have done a good job installing a solar hot water system only to be called back 2-4 weeks later to be told that the system doesn’t seem to be heating the customer’s tank.  The homeowner has been keeping a detailed log of the temperatures in the tank as well as on the roof and shows you a log that never shows the tank
sensor getting hotter than 105 degrees. They say the system has been running and they haven’t noticed anything else unusual but clearly the system isn’t working properly with the solar only getting the tank this hot.  What went wrong?

A modern differential control operates by measuring the temperature (via a temperature probe) in the bottom of the tank (T2) and the solar collector temperature at the outlet of the collector array (T1). Hot water tanks are constructed so they introduce any cold water into the bottom of the tank primarily via a dip tube that carries the cold water from the connection on
the top of the tank to the bottom of the tank. The Steca 0301U differential control (which represents greater than 50% of the control sales in the U.S.) only comes equipped with two sensors although it can take a third. In this case what the homeowner is seeing as the tank temperature is actually the temperature at the bottom of the tank (T2) where any cold water entering the tank is mixed with the solar heated water in the tank. The stratification in the tank allows the homeowner to have access to hot water (120 degrees +) at the top of the tank while only seeing “cold” water temperatures on the readout for the bottom of the tank.

solution: Supply the homeowner with a third temperature sensor that would then be mounted to the top of the tank showing what temperature the tank is actually delivering.