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October 2009, SunvalleyOnline.com
Zero Energy Buildings
“I’d like to have enough solar panels to cover all of my electrical bills.”

We’ve heard this question a lot in the past seven years. It was 2002 when Idaho Power introduced their net metering program and Whole Energy Solar began designing and installing grid-connected solar electric systems. That was when solar became a viable option for homes and businesses with access to utility electricity. Prior to that, the use of solar electricity was limited almost exclusively to remote buildings without access to utility power.

According to Idaho Power numbers, by 2009 Whole Energy Solar had installed about 30% of all the solar energy systems on their net metering program.

“Zero Energy” – the concept of producing with solar as much electricity as a home or business consumes over the year – can be difficult, but entirely possible when combined with conservation and energy efficiency. We give below two examples of “zero energy” homes with solar electric systems designed by Whole Energy Solar. But first, it makes sense to address the importance and value of being energy efficient.

For most existing homes and businesses, we point out that their current consumption would make it very expensive to purchase a solar electric system that covered their entire bill. It costs less and is a more efficient use of finances to examine your electrical use and find ways to conserve. It is also more satisfying for the owner and for us to install solar panels that meet a significant portion of their actual electrical needs. Conserving and becoming more efficient means that the same solar electric system will cover a larger portion of the building’s usage. Sometimes however, owners do choose to install solar first and then use that investment to motivate their quest for greater energy efficiency – replacing incandescent bulbs with CFLs, replacing old refrigerators or freezers, increasing insulation if heating or cooling with electricity, etc. Becoming more efficient over time will continue to make the solar fraction increase. With new construction done with electrical efficiency in mind, ” zero energy” is a more readily achievable goal.

How Much Solar for Zero Energy?
Since electrical usage varies widely among homes and businesses – depending on electrical appliances and actual usage – there is no single answer that can satisfy the question of how much solar. You have to look at actual electrical bills. But we can take a look at averages and give a sense of what’s possible.

The national average for a single family home’s electrical consumption is approximately 30 kWh per day. Idaho Power says their average home consumes 40 kWh per day – presumably more than the national average because of historically low electrical rates and a higher percentage of homes heating with electricity. Heating is something that requires large amounts of electricity.

The recent drop in solar prices has made the concept of zero energy buildings more accessible. The following table gives the approximate price of installed solar electric systems that would match the electrical use for three baseline home consumption averages. The estimated solar production is for typical installations with the amount of sun available in Boise, ID. (For locations with more sunshine the cost would be less; where the sun shines less, the cost would be more.)
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