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Get Powered Up! Certified Energy Manager Jeff Yago answers your alternative energy questions

Wondering about a great new energy-saving device
you found on the Internet? Then CLICK HERE!

Sorry. Jeff no longer answers questions online.
This will remain as a searchable
resource for all BHM website visitors.

Archive for the ‘Hot water/Water heater’ Category


Powering an electric water heater with solar

Tuesday, January 20th, 2009

Hi Jeff,

I keep reading your articles mainly for the knowledge, but you have a slight twang of humor and a hint of sarcasm in some that strikes my funny bone all the time–thank you again for the knowledge and humor!

My question for you is what calculations am I needing to figure out for how many solar panels and of what rating are needed given an example of:

Using a Tempra36 Tankless Water Heater: (unless something else is on your favorites)
090120-1for a single family residence in zip 30054 for a 2 bath house where this will be used for solely a sink basin/bath/shower, includes kitchen sink, not a dishwasher or laundry.  I don’t know yet how to address the source for the dishwasher and laundry.

In my eyes, this will be a standalone system, independent of the other solar panels used for house electric (stove, refridge, tv, comp etc); I might even put in a hot tub if the time is right.  I will assume a 120v system to simply the math for me.

I don’t know what it is I am missing, such as distance from existing water heater (which I want to move away from); the bathrooms are about 30′ apart as the crow flies.  I have no idea about the temperature of the existing water heater or of the tempature of the water incoming to the house.  I read somewhere that those numbers were relevant.

Is this something that battery power can be used for as well or would the intermittent on/offs or type of usage (heating element?) cause higher wear and tear to be too high to justify usage?

Do you have anything in your subscription that would help me address these questions or can you suggest the right occupation to get this done?  Albeit a plumber, electrician or chiropractor?

Thanks again,



The only cost you need for this calculation is the cost of a solar hot water heater as NOBODY in their right mind would install a solar electric system to power an electric hot water heater unless it was to dump excess solar power after a battery bank was charged.

For example, the table you provided indicates this electric heater has a 36 kW load.  Just as a quick comparison, grid-tie solar systems are being installed today for around $10 per watt in most states, so a solar system to power this unit will only cost  $360,000  ( $10 x 36,000 watt).

Now I realize that this 36 kW load may only be heating for a few hours per day, and your solar array may generate power for up to 5 hours per day, so you will be able to get by with only a $180,000 system.  Not to worry, as this system would provide a $54,000 tax credit under the new solar tax program towards your federal income tax, so you may not have to pay any more federal taxes for the next 22 years!

A solar hot water system sized for your family should cost in the $5,000 to $6,000 range installed, and should provide about 75 to 85% of your hot water needs.  However, if you still want to order the $180,000 solar electric hot water heater, we are running a sale through February.

Good luck,

Jeff Yago


A solar soccer complex

Tuesday, December 30th, 2008

Hi Jeff

I am building a 6 soccer field complex on a 26.77 acre lot. There is a well on the property; not sure what it pumps.

I am keen on keeping this a natural facility and happened to come across the Solar panel discussion.

Without going too deep, as I am not a technical person, would Soalr panel energy work for 1) Bathrooms, 2) Watering the sports fields?

Thank you in advance



It depends on where you live and if utility power is close by and easy to connect. If you are in a state that offers solar incentives, this can really reduce the cost for any alternative energy system. If you are not near a utility line, they may charge a very high fee to run power to a remote location. Having addressed these first, here are the solar suggestions:

1. A solar hot water system can easily provide hot water for your bathrooms and any snack bar type sink. Since your afternoon or early evening usage matches the solar afternoon peak and stored up solar heated water, you most likely would need little or no backup hot water heater.

2. It is not feasible to power any heating equipment from a small solar system, so if this location is subject to freezing weather you would either need to drain down any piping that could freeze or have heating equipment powered by the electric grid, natural gas if available, or oil/propane equipment.

3. If your only load was a well pump for ground watering you could easily install a pole mounted solar array and solar DC well pump which would provide water when the sun was shining and no pumping when the sun goes down. If you have local utility power, you will find it may be less costly to stay with a standard well pump and no solar.

4. There are a few grants for non-profits to help pay for demonstration solar projects and you may be able to find one to offset most of this cost, but I am not aware of anything for private or commercial applications.

Hope this helps, now play ball !

Jeff Yago


Solar power for hot water and dryer

Thursday, November 6th, 2008


I am trying to find information about how to run my electric dryer and hot water heater off of solar power. What I can’t find is information about using my current dryer and water heater off of batteries charged by solar panels. If that is even possible. I have a family of seven and am trying to cut down on my electric bill. Any advice you have will be greatly appreciated.

Scott Pfeiffer


Sounds like you need more than a solar power system to provide energy!

Forget the solar power for your dryer, it would cost many thousands of dollars.

However, a solar hot water heater has a much lower installed cost and with a large hot water tank could pay for itself in only a few years.

Good Luck,

Jeff Yago


Wood fired hot water

Tuesday, October 14th, 2008

We have a wood fired boiler… it is for hot water only – it needs to be replaced. Any idea where I can get a new one? The one we have is about 20 years old… it has a fire box, then the water reservoir on top. It is not used for anything other than heating water.




I addressed this question several weeks ago and I am afraid the answer has not changed. Wood-fired domestic hot water heaters are very popular in Mexico but as far as I know, none of these meet our plumbing and boiler codes for safety. I am not saying they are not safe, but there are very strict regulations on the construction, testing, and quality control that must be met and I do not believe any of these have gone through this certification process for (legal) sale in the US. I visited a manufacturer located in Eureka, California about 10 years ago who was making a really good unit, but he moved his operation to Mexico years ago.

The following is a link to unit hand-made by the Amish, but pay attention to the disclaimer note on the ad:

Hope this helps.

Jeff Yago


Wood-fired hot water

Tuesday, October 7th, 2008

Hi Jeff.

I have a small cabin and I want to build some kind of hot water shower fired by wood, something very simple CAn you lead me in the right direction? It is in the summer only that I will be using it.

Thank you.



All of these wood-fired small hot-water heaters are now only made in Mexico and are hard to import because they do not meet our plumbing and boiler codes. Up until a few years ago there was one small company in Eureka, California that was making these by hand and they were really well built. However, they went out of business in the US and the last I heard they were trying to set up production in Mexico.

Several companies make a small wood-fired hot-water heater to heat an outdoor hot tub and you may be able to use one of these if you can’t find a way to import the model from Mexico. There are many of these wood-fired hot water heaters used in less developed countries.

Good Luck,

Jeff Yago


Photovoltaics for hot water

Monday, October 6th, 2008

I am a final year b-eng building services student.

I am doing some research into PV system incorporation into building services and I have read some of your articles with interest. If possible I would would like to clarify some thoughts.

1) Would it be practical to run a PV array directly without storing the energy in batteries or inverting it to AC.

2) Would it be possible to use a system on a roof above the a toilet block where point of use water heaters are located. The system would drive a DC heating element, rated at 1.5 – 2 kW 12v.

3) At worst the system could reduce the difference between incoming and outgoing water temperature or at best provide all the required power to heat the water from ±15C° to 70C° through an instant heater. The power from one 20m2 array could power several point of use water heaters because diversity of use would ensure power demand would remain below peak.

4) Alternatively, the energy could be used to heat water in a hot water cylinder in affect a heat store. With minimal losses because power from the array goes directly to the heater element (of course circuit protection and control is necessary)

5) If my calculations are correct I should be able to heat water in a hot water cylinder with a capacity of 110 liters via a 2kW 12v DC element in just over 3.5 hours. I expect the array would span 20m2 of roof area. Higher operating voltage arrays could reduce losses further.


1) No inverter, reduced cost

2) No batteries, reduced cost and more environmentally friendly.

3) Water storage could be boosted via conventional system where necessary.


1) System usage reduced to on demand (possible life expectancy increase)

2) Payback period increased

Thank you

Mike Maher


Your calculations on energy usage may indicate to you that this will work, but you have not considered the economics. A 4 ft. X 8 ft flat plate solar hot water collector will easily heat this much water and cost around $900. A solar photovoltaic module this same size would cost over $3,000 for the same area of collection. The ONLY time we use solar pv power to heat water is with a diversion controller on a battery based solar power system for those times when the solar energy would have been lost. Otherwise, it is much cheaper to use solar thermal panels for heating and solar pv modules for non-heating type electric loads.

Anytime you cannot use solar power directly as it is generated, you will lose about 15 to 20% in the conversion process from electric energy to chemical energy, then back from chemical energy to electric energy. When you add another 5 to 10% conversion efficiency loss through the inverter and a charge controller, you end up with about 70% of the original solar energy back after storing in the batteries. This loss cannot be helped if you want to save collected solar electric energy for use later. However, heating a well insulated hot water storage tank with solar thermal heated water has much less standby losses and does not have the added energy conversion losses of a chemical battery storage system. Therefore, a direct grid tie solar power system is more efficient and lower cost than a battery based solar system to generate electrical power, but many systems still need battery storage. However, I think you will find there is a good reason solar thermal panels are still best for heating applications.

Hope this helps,

Jeff Yago


Efficient Water Heater

Friday, October 3rd, 2008

Dear Jeff,

I built my home about 23 years ago, and the original water heater is still in operation. It is a 30 gallon Rheem (natural gas). What would you suggest when I have to replace it. I would like to go as energy efficient as possible and still us gas. Thanks for all of the information you share with us.

Lee Wilkerson



After 23 years, its way past time to change that water heater!

Since your water was manufactured there have been major improvements in water heater construction, insulating materials, burner efficiency, and government efficiency regulations.

All appliances now have an energy usage tag and I would only consider those with the highest ratings. I do not know your hot water needs, but many have found the tankless water heater to be a good choice.

There are also several gas water heaters made with very-high efficiency combustion chambers which are easy to identify as they do not require a high-temperature metal flue since the water absorbs most of the heat from the flame before it gets exhausted. This is the type I have, but keep in mind it requires a small blower and several controls that use electricity, so they will not heat water if the power is out even though they are gas-fired.

Good Luck,

Jeff Yago



Tuesday, September 16th, 2008


I want to install a simple gravity fed hot water tap in my remote cabin. I am not electrified at this location. My idea is to have a water containment vessel (probably not sealed) above the heat source and copper tubing running out of the bottom of the vessel dropping to about 15 coils around a wood stove pipe. When I open the tap (which is at the lowest point) the water flowing around the coils will heat to a temp relative to the amount of heat the stovepipe is generating. Will this system work, or will the water thermosiphon back into the vessel and provide me no water at the tap? Do I need a sealed system with an inlet and outlet in the water vessel to circulate water as it heats? Thanks for the help.

Richard P.


What you described is not a thermo-siphon system, you are just passing the water around a hot pipe when you open the lower faucet and this is not safe. Without water flow, the water in the copper pipe wrapped around the stove pipe will quickly heat up and turn to steam, then “shoot” out of the tubing and back into the elevated tank.

For a thermo-siphon system to work and not overheat, you need a constant water “flow:” around the copper piping and up into the side of the tank near the top (but still below water level). The bottom end of the copper coil is connected into the bottom of the elevated tank which has to colder water (heat rises).

Your hot water supply piping to faucets should be a separate pipe connected near the top of the tank (also below the water level). As the water is heated in the coil, it will rise and enter the top of the tank, while colder water enters the coil from the bottom of the tank.

If you decide to make this a closed system and under pressure, you will need a separate temperature relief valve and a pressure relief valve, but I recommend that you keep it simple and not pressurize the tank.

Make-up cold water can be a separate cold water line connected near the bottom of the tank using either a manual valve or a “commode” type float valve to let more water in as the water level drops.

Be safe,

Jeff Yago



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