Solar water heater benefits and ROI

Back in 2006 I decided to install solar collectors for the domestic hot water system in my home in Maine.  At a purchase price of around $3000, I calculated that it paid for itself within 4.6 years (after incentives) by reducing use of propane to heat domestic hot water by nearly 50%.  I did do some modifications of my own to improve performance and I expect to save well over $11,000 in propane costs over 25 years.  

I enlisted friends and neighbors to assist in the installation and it went quite well.  Just a few hours one afternoon to get the collectors mounted, and a few more afternoons to do all the interior wiring and plumbing.

I wrote a detailed blog about the installation on my website that details the entire process of installing this well-designed kit.  I purchased the kit from Butler Sun Solutions in California and could not be more pleased with everything they provided.  The system has required little to no maintenance and continues to perform extremely well.

The chart above shows two days worth of temperature readings for the collectors and storage tank from June 17 and 18, 2020.  Click on the image to see a live version of this chart on my website.  Because the collectors are mounted vertically to the south facing wall of my house, the performance is a little compromised during the summer when the sun is higher in the sky.  (Solar collectors for work best when they are pointed directly at the sun).  I get best performance in spring and fall when the sun angle is lower and the temperatures are moderate.  Water from our well comes into the house at approximately 55°F and temperatures in the storage tank can exceed 110°F after a good sunny day.  Performance is quite good in the winter depending on outside temperatures which remain below freezing for most of the winter here in Maine.  

Preheated water from the solar storage tank is fed directly into a propane tankless demand heater that I installed in 2010 to replace the old tank water heater that failed.  By feeding pre-warmed water into the demand heater I am dramatically reducing the amount of propane needed to bring the water up to temperature.


The image above diagrams the complete system and makes it look relatively simple.  If you are comfortable doing basic household plumbing and carpentry, then this DIY kit is an excellent choice as a retrofit to reduce the energy consumption in your home and I cannot recommend Butler Sun Solutions highly enough.