Dave saves power using solar hot water heating

  • 13 July 2011
  • Home Energy Centre

Finding a “hedge” against power costs “going through the roof” led Dave to install solar hot water heating in his renovated home.

Dave had experience of both gas and electric based hot water heating systems before moving to Wellington from England.

“I was looking at some way of heating water that was less affected by the cost of power.

“When we’d left the United Kingdom power, gas and oil costs were all going up and here it was the same as well.”

He didn’t know much about solar water heating, but a hunt for advice led him to a knowledgeable plumber.

“I spoke to three or four plumbers and gas fitters, but only one had good information,” he said.

Dave had an evacuated tube solar hot water system installed.

Dave's evacuated tube solar hot water heating system on the roof of his Wellington home. “The advantage of this system is that it captures the sunlight at a variety of angles. It’s effective until 7pm in the summer where we are.

“I was also attracted by the simple design of the tube collector which has a relatively small amount of water circulating in well-insulated pipes. If a tube fails it can be replaced individually and not compromise the system, which relieved my concerns about frost damage.”

Dave says overall the system with its 30 tube collector unit and large stainless steel water tank cost $7000 to install.

“Cost efficiency wasn’t a huge motivation for what I was doing – we knew it wouldn’t pay for itself in a short period. I reckon we are probably saving about $500 a year on our power costs, which matches up with the 10-15 year pay-back in quoted case studies.

“Part of the good advice we received from our plumber was about the mix of systems we would require – we have a meter that turns on a hot water element at night when that is required, in the winter.

“In December we turn off the night-heater and won’t put it back on until the beginning of May.

“Installing everything as part of our overall renovation gave us the flexibility to specify a well-matched hot water cylinder. On sunny days the water temperature will go to 80-95 degrees Celsius or right up to boiling point. You need a cylinder that can handle that.”

“The bigger capacity – it’s a 300 litre tank – also means the hot water lasts longer. The size of the cylinder means that for the two of us we have enough hot water for four days without any additional heating.

“It’s consistently performing really well, year on year. No maintenance has been required so far.”

Dave has advice for others thinking about the solar hot water option.

“Solar energy has siting requirements, space requirements and requires specialist advice. A key factor in our decision was that the installer had carried out installations before and had information about the system. That gave us the confidence to go ahead.”









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