Solar Hot Water First. Then Photovoltaics.

solar-water heater

The solar power subsidy is an equal opportunity employer; according to Brian's post, "any solar system you purchase this year is 30% percent off, thanks to the government (or at least, you'll get a tax rebate for that much). Solar powered water heaters are eligible for 30% off, too."

But what do you get for those dollars?The evacuated tube solar hot water heaters like the one shown in the top picture are getting really cheap now that the Chinese manufacturers are cranking them out- the salesman told me that he could put one on my house for $ 3,000 and that it could serve a family of four.

That would replace a conventional electric hot water heater that uses roughly 15kWh of energy per day. A natural gas heater probably uses pretty much the same, albeit cheaper, energy. But essentially, putting that solar heater on the roof offsets 15kWh worth of energy per day from other sources.

photovoltaic-installation photo

Under average conditions, to get 15 kWh out of photovoltaics you would need a 3 kw system, batteries and inverters. At about ten bucks per watt that comes to $ 30,000.

So cost of energy from the photovoltaic system is ten times as high as that from the solar hot water system. Why would anyone put the former on their roof without the latter?

When we suggested a Big Steps in Building: Put Solar Hot Water Heaters on Every Roof Last year, we noted Eco-geek's comment that " home buyers apparently don't like to see solar water heaters disrupting their "roof lines." Others think that photovoltaics are trendier. .

But really, the people handing out tax credits should insist that you don't get money for fancy photovoltaics unless you do the cheap low hanging fruit first.

A few other big steps that would save a lot of energy and money:
Big Steps in Building: Plant a Tree
Big Steps In Building: Make Natural Ventilation Mandatory
Big Steps in Building: Install Gray Water Recovery Everywhere
Big Steps in Building: Change our Building Codes from Relative to Absolute
12 Big Steps to Make Building Better

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