Does it cost a lot of money to turn your AC fan on?
- Thread starter ManBearPig
- Start date
I leave my blower fan on 24/7 to circulate the air. It's not going to make much difference in your energy usage and may even lower it by better circulation and mixing the air.
- Aug 22, 2001
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dullard
Elite Member
- May 21, 2001
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A quick google search came up with power values from 500 W to 2000 W for the central air fan. The most informative sounding sources said it was more like 800 W to 1000 W. Of course, that will depend on the size of your fan. Lets just go with 800 W for this discussion.
The US has an average electricity price of roughly 12 cents per kWhr. Thus, having that fan on for an hour would use 10 cents. Having it on for a day would use $2.30 of electricity ($69.12/month). Cut those numbers in half if you have an efficient or small fan.
Properly placed/used space heaters and/or room air conditioners would do far better and be cheaper.
The US has an average electricity price of roughly 12 cents per kWhr. Thus, having that fan on for an hour would use 10 cents. Having it on for a day would use $2.30 of electricity ($69.12/month). Cut those numbers in half if you have an efficient or small fan.
Properly placed/used space heaters and/or room air conditioners would do far better and be cheaper.
Mermaidman
Diamond Member
- Sep 4, 2003
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Serious question:
Does leaving the AC fan on continuously (no cooling) seriously shorten the life of the unit?
Does leaving the AC fan on continuously (no cooling) seriously shorten the life of the unit?
Last edited:
angminas
Diamond Member
- Dec 17, 2006
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Window unit won't cost much...in the neighborhood of 60 watts. Central fan still uses a notable amount of electricity even when not cooling. I want to say mine is 1/3hp, which would be 250 watts or so. If you pay $0.10/kwh and leave it on 24/7/30, that's $18 a month. So...not gonna make you poor, but you'll feel it, unless having the fan on saves you money by using less cooling or something.
It's hard to know for sure, but it probably uses at least 100W.
Running it 24/7 would be 2.4kWh/day, or 8$/mo at $0.11/kWh. A large central air blower probably uses closer to what Dullard states - 250 to 500W. I'm sure 800-1000W is quite possible, but that's some serious air.
For reference, my 160CFM(small) squirrel cage fan draws 90W.
No.
Running it 24/7 would be 2.4kWh/day, or 8$/mo at $0.11/kWh. A large central air blower probably uses closer to what Dullard states - 250 to 500W. I'm sure 800-1000W is quite possible, but that's some serious air.
For reference, my 160CFM(small) squirrel cage fan draws 90W.
No.
Last edited:
Why don't you take a reading from your electrical meter, run the fan for a day and see what the meter is at. Compare it to another day where you don't run the fan (because the reading would include all the other electrical usage you have..).
Rubycon
Madame President
- Aug 10, 2005
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What kind of unit? Window, ductless, CAC (split/package system), etc.
Most air handlers (sometimes called "the furnace" by homeowners) will have the blower FLA (full load amperes) listed on the nameplate. It's also important to note if this motor is 120V or 240V as well. Multiply this value by the voltage and multiply that again by .75. (the average power factor at full load) The result is the power draw in watts.
Most people are billed by the kilowatt/hour. That is 1000 watts for one hour = one billing unit of electricity. Your electric supplier or "diesel generator man" can tell you what exactly you are paying per kWh as well.
Let's use an example of a typical four ton air handler with a 3/4hp indoor fan motor. The nameplate says 5.8 FLA and the voltage is 230V. 5.8*230*.75=1000.5. That's very close to 1kW and your calculations are approximate as you don't know the exact power factor, feed voltage AND actual amperage draw. Some motors may only be drawing 90% of FLA because of coil/filter restriction, etc. If you MUST have exact amperage and voltage you can borrow an amprobe and get these values.
In any case a 1kW load is easy to use as it will use exactly 24 units per day if you run the motor 24/7.
Multiply that by your actual rate and you will see it adds up.
Newer units also use variable speed fans and it would be assumed that placing the fan ON/OFF/AUTO switch in the ON position runs the motor at full speed. Unless there is a specific reason why you need to have this motor running it's best to leave your thermostat in the AUTO position.
As far as service life running the motor continuously most definitely will reduce its operating lifetime. If the bearings are not sealed they will need to be lubricated at more frequent intervals. This can be a PIA (although not as bad as replacing the motor!). Additionally with the fan on 24/7 the filter will need to be changed/cleaned more frequently as well. Dust may become more apparent on return grilles and/or need to be cleaned with greater frequency.
All in all it does not sound like it's worth it.
Most air handlers (sometimes called "the furnace" by homeowners) will have the blower FLA (full load amperes) listed on the nameplate. It's also important to note if this motor is 120V or 240V as well. Multiply this value by the voltage and multiply that again by .75. (the average power factor at full load) The result is the power draw in watts.
Most people are billed by the kilowatt/hour. That is 1000 watts for one hour = one billing unit of electricity. Your electric supplier or "diesel generator man" can tell you what exactly you are paying per kWh as well.
Let's use an example of a typical four ton air handler with a 3/4hp indoor fan motor. The nameplate says 5.8 FLA and the voltage is 230V. 5.8*230*.75=1000.5. That's very close to 1kW and your calculations are approximate as you don't know the exact power factor, feed voltage AND actual amperage draw. Some motors may only be drawing 90% of FLA because of coil/filter restriction, etc. If you MUST have exact amperage and voltage you can borrow an amprobe and get these values.
In any case a 1kW load is easy to use as it will use exactly 24 units per day if you run the motor 24/7.
Multiply that by your actual rate and you will see it adds up.Newer units also use variable speed fans and it would be assumed that placing the fan ON/OFF/AUTO switch in the ON position runs the motor at full speed. Unless there is a specific reason why you need to have this motor running it's best to leave your thermostat in the AUTO position.
As far as service life running the motor continuously most definitely will reduce its operating lifetime. If the bearings are not sealed they will need to be lubricated at more frequent intervals. This can be a PIA (although not as bad as replacing the motor!). Additionally with the fan on 24/7 the filter will need to be changed/cleaned more frequently as well. Dust may become more apparent on return grilles and/or need to be cleaned with greater frequency.
All in all it does not sound like it's worth it.
Rubycon
Madame President
- Aug 10, 2005
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Actually if it was so good of an idea why would it not be default? In a residential setting¹ it is not. Calculate all your interior air volume vs. the volume moved by the blower. It's not that easy without a balometer capture hood ($$$). This is before increased costs and maintenance is considered. Perhaps it MAY work better in YOUR setting but that's certainly not the rule to follow here.
__________________
¹ Residential settings often have a central return plenum rather than a dual duct system with a return duct to each room. A dual duct system may actually benefit from a fan running all the time.
That's what ceiling fans are for. They can circulate the air at a low speed. Running your giant whole house blower seems silly.
What kind of unit? Window, ductless, CAC (split/package system), etc.
Most air handlers (sometimes called "the furnace" by homeowners) will have the blower FLA (full load amperes) listed on the nameplate. It's also important to note if this motor is 120V or 240V as well. Multiply this value by the voltage and multiply that again by .75. (the average power factor at full load) The result is the power draw in watts.
Most people are billed by the kilowatt/hour. That is 1000 watts for one hour = one billing unit of electricity. Your electric supplier or "diesel generator man" can tell you what exactly you are paying per kWh as well.
Let's use an example of a typical four ton air handler with a 3/4hp indoor fan motor. The nameplate says 5.8 FLA and the voltage is 230V. 5.8*230*.75=1000.5. That's very close to 1kW and your calculations are approximate as you don't know the exact power factor, feed voltage AND actual amperage draw. Some motors may only be drawing 90% of FLA because of coil/filter restriction, etc. If you MUST have exact amperage and voltage you can borrow an amprobe and get these values.
In any case a 1kW load is easy to use as it will use exactly 24 units per day if you run the motor 24/7.
Newer units also use variable speed fans and it would be assumed that placing the fan ON/OFF/AUTO switch in the ON position runs the motor at full speed. Unless there is a specific reason why you need to have this motor running it's best to leave your thermostat in the AUTO position.
As far as service life running the motor continuously most definitely will reduce its operating lifetime. If the bearings are not sealed they will need to be lubricated at more frequent intervals. This can be a PIA (although not as bad as replacing the motor!). Additionally with the fan on 24/7 the filter will need to be changed/cleaned more frequently as well. Dust may become more apparent on return grilles and/or need to be cleaned with greater frequency.
All in all it does not sound like it's worth it.
Ooohh cool, thanks for the info! (also thanks to everyone else)
Its rated at 240v (it says 230 without heater i think?) 1.5 FLA. It's just in a little closet (i live in a largish upscale apartment).
Rubycon
Madame President
- Aug 10, 2005
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Can you post a pic of the nameplate?
That's a pretty small blower but if it runs on 240V it probably has a strip heater or is a heat pump.
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