Diy Solar Collector

DIY Solar Collector Saves Power

Matt completed the installation of his diy solar collector and water heater system in August 2009 and noted the total household electricity consumption on his monthly energy bill compared to the previous year.

The results are displayed in the graph below. On average, for the five months measured in 2009, the saving was 180 kwh.

Monthly kwh savings

Location: Indianapolis, Indiana, USA

Tank Size: 378 L (100 gal.)

DIY Builder: Matt

Configuration: Flat Plate, Active, Indirect

Insolation: 3.75 kW/m2 per day

Measurement Device: Kwh Meter

Collector Size: 5.01 m2 (54 ft2)

Cost: $1513

Detailed explanation of terms above / Share your results / More diy swh performance results

Performance Conclusions

A big thank you to Matt for making this information available so that we can all get a better idea of the performance capabilities of his home made solar water heater.

By his own admission, Matt says that his household setting is not ideal to get maximum solar efficiency, as he couldn't find the perfect spot to place his diy solar collectors.

The south side of his house has trees that block the sun at certain times of the year. During the summer the roof is in the sun, but during the winter the area below the deck gets more sun.

In addition, the roof is a 3/12 pitch so the collector tilt is much flatter than what it should be in Indianapolis, which is located at a latitude of about 40 degrees.

All these factors mean that the solar collectors only get about 4 hours of sun a day.

Matt could have put them out in the yard away from the house to ensure more sunlight exposure but that would require burying the water lines for about 125 feet and he didn't want to do that due to potential heat loss.

Using the August 2009 cost per kwh of $0.12 and the average saving figure of 180 kw/h per month, it would take about 6 years for this homemade system to pay for itself. Of course, the rate per kwh will increase every year so the payback time will probably be closer to 5 years.

Matt's DIY solar water heater performance

The graph above shows Matt's total household electricity consumption in 2008, 2009 and 2010. It's pretty obvious that the solar water heating becomes operational in August 2009 as the kwh consumption drops from that time on.

Then in January 2010 he switched from an electric tank to a tankless propane backup water heater which explains the further drop in power use.

So to sum up, considering that the solar collector setup of this system is not optimal, it still performs very effectively and is well worth the time and money invested in it.

If you ever plan on building your own solar hot water system, I've compiled a list of ten factors that can help improve a homemade solar water heaters performance.

Indianapolis Weather Conditions

The weather plays an important part in diy solar collector efficiency so here are the yearly averages for this part of the world (source: BBC Weather):

Min Temperature (°C/F)
Max Temperature (°C/F)
7 / 44.6
16 / 60.8
Sunlight Hours
Precipitation (cm/inches)
8.6 / 3.38

Compare the conditions above with the weather averages for your area to get a rough idea how efficient a similar diy solar water heater will be at your home.

System Configuration

Three diy solar collectors positioned on the roof of Matt's house heat the water flowing through them which then gets pumped down into a steel storage tank.

A copper heat exchanger inside the tank transfers heat from the water in the tank to the water flowing inside the copper exchanger which then gets delivered to the house.

This is a drainback system to prevent freezing so as soon as the pump stops working the water in the collectors and supply line drains back into the tank.

Detailed description of how Matt built his diy solar collector and the rest of his system.

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