According to the US Department of Energy (DoE), water heating consumes 14-25% of all household energy consumption (http://www.energy.gov/waterheating.htm).  In short, most of us spend a great deal of money to make sure we can take a hot shower, wash our hands in warm water, and wash our laundry and dishes in hot water.  In addition to making sure our building envelope was well insulated, I spent a great deal of time agonizing over hot water.

Given the “greenness” of our house, solar hot water was my first choice from the start.  However, a properly sized solar hot water system does not provide all your hot water during the winter months.  If it did, the system would quickly overheat during the summer months.  So, you need something else to make sure you have hot water when you need it.  Combine the cost of a solar hot water installation with another method for “finishing” or making sure it is hot and the price is became higher than I could stomach.

I did more searching and found HydroHeat (http://www.hydroheat.com).  HydroHeat produces the only ground source heat pump (GSHP) unit I could find capable of producing 100% of our hot water needs on demand.  Heat, air conditioning, and hot water from the same unit.  How cool is that!  I ordered two of them for our project through SouthEastern HVAC.  If memory serves me correctly, we waited for approximately 16 weeks and the units never came.  It was getting cold outside, and we could not afford to wait for heat any longer.  We cancelled our order for the Mega-Tek Quatro Therm units and went with Climate Master (http://www.climatemaster.com) Tranquility 27 units instead.  Now we had heat and A/C, but only byproduct hot water (via desuperheaters).

Dave from SouthEastern helped me specify and purchase a storage tank, for storing hot water made by the desuperheater, and a Noritz 94% efficient condensing propane on-demand water heater (http://www.noritz.com/homeowners/products/view/0841_series_condensing_ta...).  The Noritz unit being the most efficient propane burner we could find.  Our plumber, Steve Hogan, then helped us pipe everything in.

Naturally, I was anxious to see our “free” hot water being made by the ground source heat pumps.  I’d take sample measurements directly from the storage tank now and again.  To my dismay, I never witnessed water in the tank above 90F.  That’s a warm shower at best, and reaching that temperature was rare.  Since hot water is a by-product for the GSHPs, no hot water is made when the units are not running.  Since the house is so well insulated, the heating and cooling loads are quite low.  As a result, the pumps do not run very often, and we get very little free water heating.

The result of this?  The on demand water heater was doing its job and making hot water for us.  However, it was doing so by burning quite a bit of propane (no matter how efficiently) at over $3.00 per gallon.  It was costing us ~$100 per month just to heat our hot water.  $100 x 12 months = $1200 per year.  It sounds as if the DoE estimates are right on.  Yuck.  Given the energy efficiency of the rest of the house I hated looking at this number.  (I know, hate, is a strong word but I mean it!)

Since we have well water, our water comes into the house at ~50F regardless of the time of year.  We may use less hot water in the summer, but we still need to heat it to ~120F.  I was being forced to re-evaluate my hot water options…  Geothermal wasn’t giving us much.  On-demand propane provides plenty of hot water, but at a pretty high cost.  Electricity in our area is very expensive – about $0.18 per kWh.  Given its cost, on demand electricity would be more expensive than propane.  Natural gas is not available.  The only other practical option available is solar.  Since we live in a Northern climate, evacuated tubes are our best choice, but they can be expensive.  In fact, I found the cost to be approximately $100/tube before installation.  Ouch!

One day I found SunMaxx (http://www.sunmaxxsolar.com).  SunMaxx has evacuated tube systems that are quite a bit less than $100/tube.  In fact, I was able to purchase 40 tubes, an 80 gallon storage tank, and other miscellaneous system components (pump, expansion tank, differential controller) AND install it myself for about $4,000.  It was a tough pill to swallow, but I will get 30% back from my favorite uncle (Sam).  This brings my cost down to ~$2,800.  Not too bad considering I was first looking at evacuated tube systems that cost over $8,000.  Now, if we consider the fact that we’ve already spent over $850 on propane for hot water, our simple payback should be just 3-5 years depending on how much we make with solar and how much we use.

Please note… I got most of the copper tubing and fittings I needed for free from my Dad’s basement.  Thanks, Dad!  These materials could have easily added another $1,000 to the cost of my project.  Also, I was able to do most of the work myself with a little help getting the equipment onto the roof.  Thank you goes to my friend Shawn for that.  All this work too me quite a long time given my limited free time (and lack of funds).  If you can’t do plumbing and electrical work yourself, you are going to need to hire a plumber and an electrician, or figure out another way to get it done.

Here is something I just thought of… If you are going to build your own modular home, have the manufacturer run the plumbing and electrical for you.  Then all the onsite plumber and electrician have to do is tie them in.  This one idea will likely save you thousands if you cannot do the work yourself.  I wish I had thought of this – much – sooner!  Even if I had waited years, the plumbing and electrical work could have waited dormant in the walls for future use.  It would have saved me the pain of re-opening walls and ceilings to run the lines needed.

As times goes on, I will report on the performance of the system based on our reduction in propane use.  That will take some time since we only get propane delivered every few months.  I can say that on sunny winter days, our 80 gallon storage tank is reaching 100-110 degrees F.  This means that the on demand system only needs to bring the water up to 130F (our set temp).  This requires a 20-30 degree rise rather than an 80 degree rise in temperature (from 50F).  If we keep getting sunny days, our propane use should drop significantly, even drastically come summer.

As with other forms of energy usage, conservation of hot water almost always has a better payback than using more efficient burners.  More efficient dish washers, more efficient clothes washers, and low flow shower heads can all help.  There is a huge debate over whether a shower or a bath uses more hot water.  Rather than get into that debate, I will say this… If we start with a tank of 100F solar heated hot water, our entire family of five can each take their own shower and the water in the tank goes down to 70-80F.  If just one person takes a bath, the water in the solar tank goes from 100F down to 60F or less.  It is pretty clear to me that a bath uses much more hot water than a shower with low flow shower heads.

I hope you find this information useful.

Ed
Mr. Green Dreams