Whole house fans have been proven to significantly reduce your dependence on costly air conditioning in many cases. The reason is that summer sun causes your home to heat up, your attic becomes an oven, your ceilings become heat radiators, you walls get hot, your inside air gets hot.
I know – I lived in a 2 story home with a top floor that was about 120 M2 with just under 3 meter high ceilings. I measured the ceiling temperature as the summer days progressed. I saw temperatures in excess of 38 C at the ceiling and 32 C air under the ceiling. I installed good insulation in the attic but it did not stop the heat from going right through the insulation over time.
I found that it would take hours of running air conditioning at an input of 6000 watts to cool the air AND the walls. If I just ran air long enough to cool the air and then turned it off, the ceiling and walls would heat the air back up very quickly.
However – if the air outside was cooler than inside and I turned on my whole house fan and opened a few windows, I could run the fan for hours for pennies in energy cost. After all, the whole house fan takes just 500 watts, not 6000!
And with an air flow of 10737 M3/H (178 M3/Minute) the fan pulls all of the 360 M3 of air upstairs out in just a few minutes.
Here is an article written by a 30 year veteran in the solar power business, Jonathan Hill:
Reduce the Cost of Solar Power by $AU10,000 or More with a Whole House Fan
By Jonathan Hill, Senior Solar Design Engineer
If you are considering adding solar power to your home a whole house fan can significantly reduce the overall cost of your installation. By using energy more efficiently, you can substantially reduce the amount of electricity needed to power your home, which means far fewer panels and substantial savings.
By far the largest power drain in most homes is air conditioning in the summer. Whole house fans cool your home much more efficiently than air conditioning and solar contractors can take that into account when designing your system. In addition to being more efficient and saving you money, whole house fans also cool your home more quickly and effectively than central air conditioning. Most homes have air ducts that are connected permanently to every room forcing the system to push cold air everywhere at once. Unlike the central air system the whole house fan pulls cool air only to the rooms that are the hottest. The rooms cool down faster – sometimes in just a few minutes.
What is the real reduction in electricity cost?
How much power are we talking about? The average home air conditioner draws 25 Amps or more at 240 Volts when operating. That’s over 6000 watts. In Southern California homeowners pay from 12 to 31 cents for every kilowatt hour (kwh) of power from Southern California Edison. Houses that use a lot of air conditioning are often in the top tier of cost during air conditioning season. When air is on it can cost as much as $1.86 cents every hour the A/C runs.How much power does a whole house fan use? Most systems draw no more than about 500 Watts, or about 1/2 kilowatt per hour. At 12 cents per kilowatt-hour (KWH) that means it costs about 6 cents per hour for whole house fan cooling.
How does a whole house fan reduce the cost of solar system installation?
The solar contractor can use the lower whole house fan power usage in his/her analysis of the total power needed by your home each year. As an example it would take a 4 kw solar electric system (installed at a cost of about $13,000) to provide enough power to run the A/C for 8 hours per day between June and September! So when the lower whole house fan load is used, you save over $10,000 by reducing or eliminating that load.
Does your roof have enough area available?
Often a home’s roof might not be large enough for all the panels needed for full summer air conditioning. The 4 kw solar system mentioned above will take about 300 square feet of roof space. This just for the air conditioning! So using a whole house fan instead of air allows the system to be installed with far fewer panels so the array will better fit the available roof area. Green renewable energy is very promising both ecologically and economically, but finding a sustainable way to power our homes means increasing efficiency. Whole house fans are a practical solution to the biggest problem with energy efficiency for homeowners. While solar power is an excellent investment, sometimes the initial costs can be daunting.
Whole house fans make solar power more affordable.
For more information write me at firstname.lastname@example.org or call me at 530-559-3781 or ask your solar contractor. (Jonathan Hill is a veteran in the solar power industry having founded Sierra Solar Energy in Grass Valley, CA in 1980.)