Breadbox water heater

The solar pre-hot water heater warms the water before going to a normal water heater. In this way the hot water heater does not work as much, saving energy. On sunny days in early fall/late spring the water going into the water heater is warmer than the water coming out giving us "FREE" hot water. Overall I estimate it saves about 1/3 of our hot water bill or about $5/month. Probably not worth the effort in hind sight. Additionally we added an insulating blanket to the water heater to reduce standing heat losses. For our family of 4 we use about 10 CCF of gas a month for our dryer and hot water.

An offsetting savings to the tanks is we purchased smaller water heater. We had a 30 gal electric heater our first home and never had a problem running out of hot water, even when we had 12 people staying with us. In our second home we use a 40 gal gas water heater, larger due to the Jacuzzi tub which is frequently used, and again no problem. In a normal 3.5 bath house an 80 gal tank is recommended.

In our first house we used a single tank that held 42 gallons. In the bottom of the enclosure we had about 100 pounds of rocks to act as a heat sink keeping the water from getting too hot and to help retain heat through the night.

We removed some of the insulation from below the enclosure so heat from the house ensures it will not freeze.

It worked as even on a cold December morning after a low of 6 degrees F the water going into the hot water heater was 2 degrees warmer than the cold water out of the tap.

In the new house we used a double stage design and added a temperature probe to see how well it works. We did not remove any insulation so there is little warming from the house. In this design I have about 60 gallons of water being heated by the sun.

By early morning when the temperature is in the low teens the water can drop to 40, a few degrees lower than ground temp but overall it helps.

	Out Temp	In Temp	BTU's Solar	BTU's Needed	% Saved
October	89	68	12070	29952	40%
November	78	61	9845	33792	29%
December	58	54	5998	33792	13%
January	58	48	5532	41472	13%
February	69	48	12326	41472	30%
March	73	53	11496	38592	30%
April	86	62	14106	33600	42%
May	89	65	13577	31680	43%
June	90	70	11472	28800	40%
July	91	74	10005	26496	38%
August	93	75	10605	25920	41%
September	94	75	10996	25920	42%
	Gallons used/day		80
	$/Kilowatt		$.065
	BTU's Saved		9,068		33%
	KW/Month Saved		80
	$ /month		$5.18

In the second house I recorded three temperatures/day, late afternoon, at night after showers or baths, and then early in the morning. I had at least 35 measurements for each month listed. With no heat going into the box except solar we barely held our own in December. But through the fall, spring and summer, it provided a good portion of our hot water.

With the Jacuzzi tub our hot water usage is probably a bit more than the average family.

I have tried to offset the tub by adding low flow shower heads and adapters for our faucets. After I did this our water usage seemed to drop from 45,000 gal to 41,000 gal per month. If you want to reduce hot water usage a good web site for energy saving shower heads and other products is http://www.estewards.com.