We are remodeling our home. What pipes and wiring will we need in the future to install solar PV and water-heating (when we have the $)?

Asked by Doug
Oakland, CA

Our home is in Oakland, CA, in a 1700-sq-ft, flat-roofed house. We are currently doing a gut remodel, deconstructed down to the studs. We haven't moved in, so we don't know the utility usage, but there are just two of us, and we plan to use all energy-efficient lights, fixtures, and appliances. The home is 2 stories with an unfinished basement, and we plan to install greywater recycling and a tankless water heater.


Pete Gang, AIA, LEED-AP BD+C

Answered by Pete Gang, AIA, LEED-AP BD+C

Petaluma, CA

Common Sense Design

November 8, 2010

First, try to imagine the PV panels and solar collectors (water-heating panels) in place on your flat roof. To get you started, I'll make some quick assumptions about the roof-mounted components based on what you've told us:

  1. the PV panels and solar collectors will face south or southwest and be located so that shading is minimized year-round,
  2. your PV system will be in the range of 2 to 3 kW in size and take up less than 250 square feet of roof area,
  3. you will have two 4'x8' solar collectors.

To anticipate the PV solar power system,

  • you will need to run a single 1" conduit from your main breaker panel up to a weathertight junction box in an accessible location near the perimeter of the panel array on the roof.
  • You will also need space in your breaker panel -- I will guess 30 amps -- for circuit breakers for the PV system.

To anticipate the collectors for the solar water heating system,

  • you will need to run two insulated pipes (probably 3/4" or 1" copper) from your water heater location up to the roof and near the edge of the solar collectors.
  • If you have an attic, you might initially terminate these pipes in the attic instead of running them up through the roof.

Also, assuming the runs are short, I would suggest that you locate your demand water heater in an insulated, well-vented mechanical area -- or room -- in the basement that is large enough to accommodate a 120 gallon+ storage tank for the solar water system.

That should get you started!

I would strongly recommend that you get input from trusted solar installers -- a PV solar contractor and a solar hot water contractor before much further down the road!


For more information:

Read Robert & Christine Boles's Q&A "How much will it cost to install solar panels on my 2,000-sq.-ft. home in San Francisco?"

Read Florian Speier's Q&A "We are planning a new home (still 2-3 years out). Is solar a viable (cost-effective) solution?"

Tagged In: solar panels, solar water heater

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