Question

I want to help get my mom's house "off the grid." Where do I start?

Asked by Jackie Mellen, Chipley, FL

I want to help get my mom's house "off the grid." She lives in a rural area where wind and solar power are feasible energy alternatives. Where do I start?

Answer

Florian Speier

Answered by Florian Speier

San Francisco, CA

Zeitgeist Sustainable Residential Design

October 3, 2008

There are two main things we need to discuss for your project:

  1. Do you really want to be "off the grid"—as in disconnected from it? It is usually more economical and more environmentally friendly to stay connected, even if you produce all your own energy.
  2. Once you have made that decision, we can look into the different ways of producing your own energy and reducing your usage.

The grid and net metering

The biggest problem of getting off the grid is that the alternative energy sources we have—wind and solar, in your case—don't produce the amount of energy you need at the moment you need it.

So going off the grid requires you to store energy, and that means batteries. Unfortunately, batteries are very expensive, have limited capacity, and contain toxic substances.

For houses that are (or can be) connected to the grid, it is usually preferable to use a technology called net metering. Basically, you use the grid as a giant battery. You feed power into it when you produce more than you need, and take power from it when you need more than you produce. No power gets wasted, because the electricity companies lower the output of their coal-burning power plants by the amount of electricity you put into the grid. You avoid the expense of batteries, and in most states you get paid very well for feeding the grid.

Selecting a source of alternative energy

In nearly all areas, the most feasible alternative energy system is solar thermal for domestic hot water (and for heating if you can use a hydronic hot-water heating system). I recommend you start with solar hot water because this is a very simple technology that is easy to add to most homes at a moderate cost.

Once you have solar hot water in place, your options for alternative sources of energy are wind and solar electric. In deciding between the two of them, the key factors are your average wind speed and solar radiation. As a rule of thumb, wind energy becomes competitive for properties with average wind speeds of 10 mph or more. The website of the American Wind Energy Association is a starting point to research this. When I searched for your location, the closest data I found was for Tallahassee, Florida, where unfortunately the reported average wind speed of 6.2 mph is too low. Unless your house is located on a ridge, or topography channels winds into your immediate area, I doubt wind will be a feasible energy source.

Solar, on the other hand, is quite efficient in Florida, so the first step would be to contact a provider and have them prepare a proposal that clearly shows the amount of energy produced in a year and the cost. You can find providers at www.findsolar.com (the website also has a calculator to help you estimate system size and cost). The next step is to look into tax rebates and government incentives available in your area. You will get a federal income tax rebate for 30 percent of the system cost, and the state of Florida will contribute another $4 per installed Watt. A solar hot-water system would also qualify you for a $500 credit. You can find more information on this topic at the Florida Renewable Energy Association's website.

Reducing your usage is easier than producing power

While it feels great to produce your own power sustainably, it is just as good for the environment to reduce your consumption. Many residences can cut their power needs in half with relatively minor measures.

In Florida, this means cutting the load on the air-conditioning system by allowing less heat to enter the house. Obviously, a well insulated and sealed house with high-quality windows is ideal, but everyone has to work with what is already there. Attic insulation can often be upgraded easily: Energy Star recommends a minimum of R-30 for attic insulation in your area and the Department of Energy recommends R-38 to R-49. The additional cost of going to a higher R-value is often very small, so I would follow the higher recommendations.

If you replace any windows, study the label on the product by the National Fenestration Rating Council. There are two main values, the U-Factor and the Solar Heat Gain Coefficient. For both values, lower is better, but they measure very different things. U-Factor describes how much heat moves through the window due to the air temperature difference between inside and outside. That is important, but in Florida the Solar Heat Gain Coefficient (SHGC) is much more important, especially on south and west facades. SHGC describes how much of the energy in a sun ray that hits the window will enter your house. A value of 0.32 means that 32 percent of the ray's energy ends up as heat indoors that your air conditioner has to move back outdoors. Energy Star recommends an SHGC of 0.35 or less for your area.

Another way to reduce heat gain is to shade windows to the south and east externally. Parapets can often be added on the south facade. On the west side of the house they are inefficient, as the low-standing evening sun shines underneath them—opt for external shutters instead. These are many times more efficient than shades or shutters on the inside of the window.

Tagged In: solar panels, summer energy, solar water heater, energy tax credit, wind power

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