Solar Water Heating Update

Solar water heating production.Last October we installed a solar water heating system on our home. It has been about ten months and I thought this would be a good time for a promised update. Overall, we are very pleased with the results so far.

Solar Water Heating System

Our system was manufactured by Heliodyne in Richmond, California. I like that it is made in the U.S. and is relatively local. It consists of one 4’ x 10’ flat plate collector on the roof and a 75-gallon water tank (with natural gas backup) in the garage. Space is at a premium in our two-car garage, since we actually park two cars and a bunch of other stuff in it, and the single-tank system has the same footprint of our previous 50-gallon tank.

The water tank is just like a standard, well-insulated gas-fired water heater with some extra connections to accommodate the solar component. It serves as a backup and is set to automatically turn on just like a regular water heater when necessary. During the summer, it is a rare occasion, but during winter it regularly supplements the reduced solar contribution.

Monitoring Performance

There are two ways to monitor the system’s performance. First, the controller has software that provides information directly to our home computer. Secondly, I compare our bills from Southwest Gas. Neither provides a precise account of actual savings because there are many factors that blur the data. I know how much energy the system collects from the sun, but how much of that solar energy is actually used to offset our use of natural gas is not as clear because we also use natural gas for cooking, space heating and clothes drying. Plus, the new system is set to provide hotter water than we had before, something we enjoy quite a bit.

Bottom Line – 33%

The bottom line is that even with the water set to a higher average temperature, we have cut our use of natural gas considerably. Average yearly consumption for the entire home is expected to be approximately 33% lower, with a monthly maximum reduction of 63% so far. Although I do not know exactly what the percentage is for just the hot water, I can say that the system performance has so far exceeded its official rating by about 20%.

Unlike photovoltaic systems that can send excess energy back into the grid for credits that can be redeemed in the future, solar hot water is a “use it or lose it” resource. There is no way to shove that excess thermal energy back into the pipe to the benefit of Southwest Gas or its other customers. In general, those who use the most hot water, whether larger families or commercial businesses, will get the greatest bang for their solar-water-heating buck. Our particular situation is the opposite and therefore more of a worst-case scenario when it comes to payback. No matter how you slice it though, a solar water heater is the only kind I know with any payback at all.

What’s the Payback?

Payback comes in many forms, and the simple savings is by far the least important. Natural gas is now very cheap, due to the increasingly widespread practice of hydraulic fracturing, otherwise known as fracking. The process injects a toxic brew of chemicals into the ground, fracturing the rock to release gas and other by-products. It is far from benign. Aquifers are being poisoned forever and an increasing number of people, our fellow citizens, friends and family, are getting seriously ill as their property values plummet to zero.

Please take a few minutes to watch this video that illustrates the effects of our energy choices:

My computer shows a chart of red bars indicating how much energy our system has produced (click on the thumbnail above for a better view). Every increment on each of those bright red bars means one less unit of natural gas burned, one less bit of water poisoned, and fewer friends (human and non-human alike) damaged by the relentless quest for fossil fuel profit at any cost. There are many who can afford solar water heaters. Imagine the impact we will have when they are on every rooftop! They are already commonplace in several other countries. Why are we so far behind?

This is a good time to install a system. Incentives are strong now, but they come and go. If you can afford it, please invest in our collective future. That is what Green Living is all about.


  1. chuck kuhn says

    One has to weight the inital cost of solar water system and How much they use in gas yearly to justify the cost/difference. Couple retired (2) are gas bill for water is maybe $30 month. Not against new energy systems, I have 28 solar panels that give me Free electricity for the last 2 yrs. The break even point is est. 7 years. Now if you have electric water heater, I think this offers more a saving $$ long term. Just my 2 cents, because I initially looked at Solar for Water 2 yrs ago, and switched to Solar panels for electricity.

    • It’s great to hear from another solar homeowner!

      You are correct on the cost issue except that you are only referring to *your* cost. For me, it is the horrific cost to others and to our environment that most drives me to invest in clean energy. I want to minimize my use of any product that does harm.

      There is much more to life than a few extra dollars. Of course not everyone is in a position to make that choice, but there are many who are. Those are the people I hope to influence.

  2. jim rothstein says

    Very useful article and comments.

    I am curious about payback time, too. I read these can be a bit high and not sure just why or where the problems are.

    I also wonder how if Southwest Gas’ releases any aggregate data on subscribers to its incentive/rebate programs.