A quick look at how an AirScape whole house fan stacks up in terms of saving money and reducing carbon emissions by saving electricity.

The first thing to know: saving electricity reduces your carbon footprint.

A lot of consumers equate their carbon output with driving. But simply running your computer creates carbon emissions too. That’s because much of the electricity in the US is generated by coal. Looking at US Department of Energy figures, the average kW generated in the US creates about 1.36 pounds of C02 emissions. So when you save electricity, you’re not just saving money, you’re helping to reduce carbon emissions that are causing global warming.

It’s all about using the least amount of energy for the task at hand

To me, using the least possible energy for a given purpose goes beyond green, it’s just plain sensible. Use what you need to get the job done, but no more than necessary. In any system design, this is a core engineering principle.

You need electric light in your house. Why would you use an old incandescent 60W bulb, when you can use a new 12W CFL bulb to provide the same light (and much less heat)? This same principle drives us in promoting whole house fans. Why would you run an air conditioner that may use 2-3000 Watts or more, when you could use a whole house fan to accomplish the same task and use 140 Watts or less? (I don’t mean to imply here that a WHF is the same as an Air Conditioner, but in the right circumstances they both do the same job: keep your living space comfortable.)

How an AirScape WHF compares as a green option for your home

For a long time I’ve been curious to do a little comparison, so , using numbers from my own experience combined with various other sources, I finally made up a spreadsheet. The idea is to compare an AirScape fan with CFL bulbs on one hand and a solar system on the other, comparing not just energy and C02 emission savings, but also the financial cost of those savings.

Now bear in mind that I needed to make a lot of assumptions on variables that are, well, widely variable. So you should consider this simply an example rather than some predictive model for your situation. This is based on my own situation and experience, as I have implemented all three technologies in my own home and, being the energy-saving geek that I am, have followed the energy curves closely over the years.

Here’s the results distilled into three charts:

A final word about solar and being green

I don’t mean to imply that solar is a bad idea—it’s a great idea. It’s green and clean, and the more solar power we generate, the better off the planet will be. The only problem is that it is still expensive and doesn’t have as impressive an ROI as other options. However, with rebate programs rising and prices dropping every year, that’s changing. I urge everyone I know to install a solar system if they can afford it.

Of course, I also urge everyone I know to install a whole house fan, which is a lot more affordable, has a more compelling financial case and is a great under-appreciated way to become a little greener.

• 1900 sq ft home in San Jose CA
• incremental blended energy cost of 0.25 per kW/h (this is high, but that’s California for you!)
• DOE average carbon output of 1.36 lbs per kW/h
• about 1200 hours of cooling operation per year (for either A/C or WHF)
• WHF operation replaces 1.5 tons of AC cooling at 1.2 kW per ton efficiency
  (this is the mushiest assumption but after years of experience both in my own home and in commercial ventilation I confident it is reasonable)
• replacing 60W incandescent bulbs with 12W CFL bulbs in 20 locations, with each bulb operating an average of 5 hours per day
• 2kW solar system generating full output for an average of 5 hours every day of the year

If you are interested in diving deeper into these calculations, Give me a ring @ 1.866.448.4187—I’d be happy to chat about them.

Posted by Neil Smith on November 29, 2007