Zero Energy Homes Consume… More Than Zero Energy

Todays Seattle Times contains a front page article about homes that consume “zero energy”. The problem is when you read the fine print, zero energy is really 50% or 59% or 70% or… now I did not major in math…. Wait a minute, I did major in math… should not a zero energy home consume approximately 100% less than what a normal house consumes, give or take 0 percent?

The 10 energy-saving town houses in the Issaquah Highlands will be aimed at the median market.
"We don't want this to be for an exclusive few," he said

According to preliminary plans, the homes will range from 500 to 1,700 square feet.

The features could tack about $100,000 on to the Issaquah units, Liljequist said.

That is $100,000 PER 500 to 1700 sf unit.

If homeowners produce more electricity than they use, utility companies are required to credit them for it under Washington's net-metering law. And, under a state law that took effect last year, those who generate solar energy for the power grid could earn up to $2,000 a year in cash reimbursements through 2014.

Spend $100,000 and earn up to $2,000 a year through 2014. Run that past an econ major.

Now the Seattle Times touts dual glazed windows, heavy duty insulation, high efficiency appliances and compact fluorescent light bulbs. Now all of these are great at REDUCING energy consumption but in order to be zero energy, you will need to produce the same amount as you use. So they also talk about solar panels. So how effective are solar panels?

From, How many solar cells would I need in order to provide all of the electricity that my house needs?
Assumes 5 hours of sunlight a day...

From our calculations and assumptions above, we know that a solar panel can generate 70 milliwatts per square inch * 5 hours = 350 milliwatt hours per day. Therefore you need about 41,000 square inches of solar panel for the house. That's a solar panel that measures about 285 square feet (about 26 square meters). That would cost around $16,000 right now. Then, because the sun only shines part of the time, you would need to purchase a battery bank, an inverter, etc., and that often doubles the cost of the installation.

If you want to have a small room air conditioner in your bedroom, double everything.

The thing to remember, however, is that 100 watts per hour purchased from the power grid would only cost about 24 cents a day right now, or $91 a year. That's why you don't see many solar houses unless they are in very remote locations. When it only costs about $100 a year to purchase power from the grid, it is hard to justify spending thousands of dollars on a solar system.