DIY Solar Water Heater

DIY Solar Water Heater Field Performance Results

It's true that a diy solar water heater costs a lot less than a commercial one for the homeowner but what isn't as clear is how much the performance suffers due to the fact that the system is homemade.

Does cheaper necessarily mean worse in terms of performance?

Is it possible to build a system yourself that can heat water as well as the professionally designed, built and installed units costing thousands more?

The measured efficiency results listed below specifically from diy solar water heaters already installed in homes worldwide hold the answers.

They were measured by the system builders themselves using a variety of different temperature and energy monitors.

If you've built and installed your own diy solar water heater, please consider making a planet saving difference by measuring the efficiency of your system and sharing the results with me here.

DIY Solar Water Heater Efficiency Results

Insolation: 3.75 kW/m2 per day

Performance Indicator: Electricity Saved (kwh)

DIY Builder: Matt

Tank Size: 378 l (100 gal.)

Collector Size: 5.01 m2 (54 ft2)

Configuration: Flat Plate, Active, Indirect

Cost: $1513 US

When building your own DIY solar water heater system it's useful to have an idea of whether it's going to be worth all your time, effort and money.

Matt was kind enough to send me the figures of his household electricity bill before and after the installation of the system he built in August 2009.

This allowed me to work out how much the system was saving him every month and the expected payback time...

Matt's diy solar collector and system performance.

Insolation: 3.73 kW/m2 per day

Performance Indicator: Tank, Collector Temperature

DIY Builder: Gary Resa

Tank Size: 620 l (164 gal.)

Collector Size: 4.83 m2 (52 ft2)

Configuration: Flat Plate, Active, Indirect

Hot Water Demand: 90 l (24 gal.) per day, 2 people

Cost: Under $1000 US

Gary built his system in 2008 and charted its performance for the next 8 months in which time it achieved a solar fraction of 94%, which is astonishing considering the harsh winters that Montana can experience.

He made use of an Onset U12, 4 channel data logger with four temperature sensors connected to measure the efficiency of the diy solar collector and tank.

It's a testament to the quality of the design and construction that it does so well, along with a few other factors which Gary mentions, as well as discussing at length how he went about building the system.

This is 'must read' material if you have any interest at all in building your own solar hot water system...

Gary's diy solar water heater performance and build.

Insolation: 3.23 kW/m2 per day

Performance Indicator: Tank, Collector Temperature

DIY Builder: Kevin Sharman

Tank Size: 620 l (164 gal.)

Collector Size: 6.41 m2 (69 ft2)

Configuration: Flat Plate, Active, Indirect

Hot Water Demand: 215 l (57 gal.) per day

Cost: Approximately $1600 US

Kevin started measuring the efficiency of his homemade solar water heater in May 2009 until March 2010 using a PICAXE 18X 4 channel datalogger.

He rigged his own temperature probes by taking a piece of steel antenna from the dump, wiring up a DS18B20 temperature sensor, and then encasing the sensor in epoxy inside the piece of antenna.

The results of his efficiency measurements was a solar fraction of 84%, not bad if you take into account temperatures drop to minus 40° C (minus 40° F ) in Tumbler Ridge BC on occasion.

Kevin's system performance and construction.

Insolation: 2.77 kW/m2 per day

Performance Indicator: Tank Temperature

DIY Builder: Niel

Tank Size: 800 l (211 gal.)

Collector Size: 11.52 m2 (124 ft2)

Configuration: Flat Plate, Active, Indirect

Cost: Approximately £1700 Sterling

Niel hasn't been measuring the efficiency of his diy solar hot water heater system long enough to be able to determine the solar fraction yet but initial results in May 2010 showed the top tank temperature fluctuating between 45° C (113° F ) and 68° C (154° F ).

Hopefully Niel will provide more comprehensive figures in future but there is a lot to be learnt from the way in which he designed and constructed the diy solar water panel and tank.

Chart of the performance results and full description of the system.

Insolation: 3.66 kW/m2 per day

Performance Indicator: Tank, Collector Temperature

DIY Builder: Eric

Tank Size: 757 l (200 gal.)

Collector Size: 3.71 m2 (40 ft2)

Configuration: Flat Plate, Active, Indirect

Real time measurement is first prize when it comes to performance results and Eric makes use of the IO-204 module from IoBridge to display the live temperature readings of the tank, collector and outdoor temperature.

He didn't build the components of the system himself but bought them from various places and then installed them all, so it does still qualify as a diy solar water heater.

See the live performance results of Eric's system.

Conclusions Based on Measured Performance Results

Looking at the results that the DIY solar water heaters are achieving the conclusion can be drawn that given the correct design and construction it definitely is possible for a home made and installed system to perform as well as its commercial counterparts.

As long as you take the following ten factors into account when you design and build your homemade solar water heater, as I did for my own DIY flat plate solar collector.

Solar thermal diy is still not cheap, as the systems above cost from just under US$1000 up to US$2800 to build, but in comparison to the professional systems that is very affordable. So if you are willing to put in the work yourself and build a diy solar water heater, you can save a lot of money and still get very good hot water performance.

Top 3 Commercial Solar Water Heaters

These are the top three solar water heaters manufactured and installed commercially in various areas of the world, ranked by efficiency results.