Real garages.
Real savings.
Garage exhaust fans are some of the biggest motors in a building, and many of them run on a time clock or around the clock. A CO detection system runs them only when the air needs it. Here is what that looked like in four garages we have worked on, using the buildings’ own numbers. Building names are withheld at our customers’ request.
At a glance: savings then and today
| Building | Fan runtime cut | Energy savings per year, then | Same savings at today’s rates |
|---|---|---|---|
| Office tower, downtown Los Angeles | 84% | $37,000 | $63,300 |
| Office building, Century City | 88% | $27,600 | $46,900 |
| High-rise, downtown Los Angeles | 94% | $32,400 | $55,200 |
| University recreation center, Bay Area | n/a | $35,000 | $50,800 |
The three Los Angeles projects were calculated at 10 cents per kWh, which matched California commercial rates at the time. Today’s figures use 17 cents per kWh for Los Angeles and 19 cents for the Bay Area. The Bay Area project was calculated at 2010 rates (13.1 cents per kWh).
150 hp of exhaust fans, installed 1998
Office tower, downtown Los Angeles
The problem
The garage ran 150 horsepower of exhaust fans on time clocks, 3,744 hours a year. Time clocks alone did not meet the California Mechanical Code, and the fans ran whether or not a single car was moving.
What we did
We installed a CO detection system that starts the fans only when carbon monoxide rises, plus soft starters on the fan motors and an air balance. The project cost $55,000.
The result
Fan runtime dropped to 599 hours a year. Over 13 years the building saved more than 4.5 million kWh and $413,327 net, after paying for the installation and every year of maintenance and parts. The savings were measured by data loggers the property installed itself, independent of us.
At the time: about $37,000 a year in energy savings. At today’s rates: about $63,300 a year.
120 hp of exhaust fans, installed 1997
Office building, Century City
The problem
120 horsepower of garage exhaust fans ran on a time clock, about 3,432 hours a year.
What we did
We installed a CO detection system to run the fans on demand. The installation cost $52,822.
The result
The fans now run about 400 hours a year. Over 14 years the building saved $290,580 net compared with the old time clock schedule, after the installation and all maintenance and parts.
At the time: about $27,600 a year in energy savings. At today’s rates: about $46,900 a year.
50 hp of exhaust fans, installed 2003
High-rise, downtown Los Angeles
The problem
The garage exhaust fans, 50 horsepower in total, ran 24 hours a day, 8,760 hours a year.
What we did
We installed a CO detection system to control the fans. The project cost $55,000.
The result
Fan runtime fell to about 547 hours a year. Over 8 years the building saved $196,982 net, after the installation and all maintenance and parts.
At the time: about $32,400 a year in energy savings. At today’s rates: about $55,200 a year.
Six exhaust fans, installed 2010
University recreation center, Bay Area
The problem
Six large exhaust fans ran continuously, including overnight and mid-day when almost no cars were moving.
What we did
We installed 14 CO sensors that control five of the six fans. The sixth still runs because it ventilates mechanical spaces. As a safety measure, all fans turn on if the system detects a malfunction.
The result
The university put current monitors on the fans for a month to verify the system: the fans came on only every few days. It saves about $35,000 a year and roughly 100 metric tons of greenhouse gas emissions. With a $50,000 utility rebate, it paid for itself in under six months. The university published the results in its own sustainability newsletter.
At the time: about $35,000 a year in energy savings. At today’s rates: about $50,800 a year.
What we see in the field
The power light was on. The system was dead.
A company moved its headquarters into a building in Burbank. The engineers were told the garage CO system worked because the fans came on when someone held a cigarette under a sensor. They had it tested properly anyway. We could not get a single sensor to start the fans, even at 200 ppm. The power lights were on, so everyone had assumed it was working. We checked a sample on each of the five levels to confirm, and the money went toward a new system instead.
Fans on a time clock, a busy Sunday night
A large parking structure in downtown Los Angeles ran its exhaust fans on time clocks, switched off on weekends. One Sunday evening a big event let out, exit lines backed up across 11 levels, and a parking attendant ended up in the hospital with carbon monoxide poisoning. The owner then installed a full CO detection system, 89 sensors, so the fans respond to the air instead of the calendar.
If your garage fans run on a time clock or never shut off, see garage ventilation and VFD energy savings or upgrading an existing system.
Common questions
How much can a CO detection system save in a parking garage?
In the projects on this page, fan runtime dropped between 84% and 94%, and net savings ran from about $197,000 to $413,000 per building over 8 to 14 years. Those figures used electricity at about 10 cents per kWh. At today’s rates of about 17 to 19 cents, the same projects would save roughly 1.5 to 1.7 times as much on energy.
How long does a garage CO system take to pay for itself?
In these projects, payback ranged from under six months, with a utility rebate, to about two years. Bigger fans, longer existing run hours and higher electricity rates all shorten it.
Why did these garages save so much?
The fans were running on time clocks or around the clock. A CO system only runs them when carbon monoxide levels rise, which in most garages is a small fraction of the day.
What would your garage save?
Tell us the building, the fan sizes and how they run today. We will tell you what a CO system would change, no pressure.