How to reduce power bill

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Old 07-10-14, 03:07 AM
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How to reduce power bill

So I was kinda shocked when I got this month's power bill. I just recently had a 22000 BTU split AC installed in my office, and my power bill is over $1100 a month. A jump of $200 from what I regularly pay.

Right now I'm trying to see how I can save on my bill without being cooked in my office from the summer heat.

The AC is a Midea 22K BTU Split type inverter AC. Input power is 2200W and SEER is 15.

I have the AC set on Dry mode at 80F, and it's pretty cool. Does this affect my power bill if I just leave it on Dry Mode?

Also does the Input mean it's constantly drawing 2200W no matter what setting I have the AC on, or does it vary on what I do with the AC?

KWH here is $0.41-$0.48 depending if I use more or less than 500 KWH per month. So any suggestions is appreciated!
 
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Old 07-10-14, 03:15 AM
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It's on usually from 10am to 11pm everyday.
 
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Old 07-10-14, 03:52 AM
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No idea as to the dry mode . We live in a mostly dry climate so I have never used it on ours .

I put it on cool and set the temp to 74 .

How many square feet is the office ?

A lot of heat producing equipment in the office ? Thinking lots of PC's with old CRT monitors ? Several coffee pots or copy machines ? Lots of incandescent light fixtures ?

Check the condenser unit . Is it getting adequate air flow in and out of the unit ? Are the copper lines well insulated ?

What is the temperature of the air coming out of the indoor unit ? Is the filter already stopped up ?

Lastly , is it low on refrigerant ?

God bless
Wyr
 
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Old 07-10-14, 05:03 AM
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Ouch! Your electricity rate is almost 4 1/2 times mine at 9.3 cents per KWH.

You said that your bill went up by $200 when you installed the AC. So, we can assume that $900 of your bill is for things other than your AC. If I adjust the $200 AC portion to my energy rate it's about $44 which seems reasonable. Since other uses are the lion's share of your bill I would focus on them. And, as WyrTwister poineted out all those other things consuming electricity are generating heat which you have to pay to cool.
 
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Old 07-10-14, 05:50 AM
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The office is pretty much empty it's about 800sqf with a 12ft high concrete ceiling, other than one small refrigerator and a computer. Most of the power bill comes from outside the office like the central AC, and other home appliances. I'm okay with $800-$900 a month, but it seems excessive that a new AC jumps it up $200.

It's been pretty stable at $800-$880 a month for the past year so I know it's the new AC that jumped it up $200.

It's brand new so the filters are still new. The outdoor unit and lines are well insulated, and the air coming out of the AC is good. I always ran the temperature last month at 78F on Auto, and the humidity level is at 50%-55%

I also replaced all the lights with CFL bulbs a good while ago. No incandescent are in the office.

Also is the rated Input of 2200W means it always uses 2200W no matter what?
 
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Old 07-10-14, 06:49 AM
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Do you think a programmable thermostat would work to save me costs? Can a thermostat turn on a AC for 30mins and turn it off after 30mins for 24 hours?
 
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Old 07-10-14, 07:10 AM
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Most programmable thermostats have 4 programmable time/temperature settings. So, for example if you want your A/C to come on for 30 min, let's say from 9:00 to 9:30, you could setup a program such as the following:

Program# Time Temp
1 9:00AM 70
2 9:10AM 70
3 9:20AM 70
4 9:30AM 90

Of course, you can set the temperature to be whatever you want. I picked 70 and 90 as extremes to ensure that it would turn on/off.
 
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Old 07-10-14, 08:39 AM
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Did you replace an old AC unit with this new one ? or this is a new addition ? An AC unit of 22000 btu costs $44/month to run, that is reasonable.
 
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Old 07-10-14, 10:10 AM
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Just to be clear...this is probably a mini-split A/C yes? No ducts or anything? Can't imagine it running that high unless the increased demand put you over some sort of price point. If it's a mini-split, doubt you can add any type of stat, since theirs are normally built in.

I don't think I can adequately explain the "dry mode" but basically it's acting as a dehumidifier all the time, even if it's at the set temp for cooling. It's kind of big for the size room you have, though the 12ft ceilings may put it in the right range. For a regular room (8ft ceilings) a window unit would only need to be about 15-17K btu.

No...the 2200 watts is not being drawn all the time, that's the max it would draw under normal full load conditions.
 
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Old 07-11-14, 01:08 AM
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Try it on regular cool mode for a month .

What was the RH before you installed the mini split ?

You also have a conventional central A/C serving the area ?

This is a home office ?

Can you shut off the central A/C or close off the vents / frills to the office ?

Consider a 8' drop ceiling with a lot of insulation on top of the pads .

God bless
Wyr
 
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Old 07-29-14, 05:00 AM
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Okay folks I got an update

I bought an Efergy E2 whole house power monitor to see what the AC was using.

Using it on Auto Mode the AC used 1900W-2000W and drops down to 1200W when it has reached the temperature.

However DRY Mode which keeps the whole office cold only uses 600W and cools the office as fast as auto mode.
 
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Old 07-30-14, 12:44 AM
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That doesn't look correct in auto mode. 1900-2000 watts is normal with the inside fan and the compressor unit running but when the compressor shuts down when temperature is reached the system should not continue to draw 1200watts.

DRY mode using 600w of power cannot cool the same as the auto or on mode. I can see it maybe keeping the office cold once the temperature is down.
 
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Old 07-30-14, 03:00 AM
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As you say , once the space is cool , dry mode may be enough to maintain temperature .

Two observations .

A - the unit may be OVERSIZED ?

B - Probably an variable speed / inverter powered compressor ?

I do not think my unit has a dry mode ? We live in a dry climate ( most of the time ) and would not have had an occasion to use it .

Check it in plain COOL mode & not Auto mode . I leave my inside fan on HIGH all the time to help circulate air .

Do the mini split compressors have a crankcase heater like a conventional residential split system ?

God bless
Wyr
 
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Old 07-30-14, 04:44 AM
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If U have a way to check CFM to each room U can check the temp-drop * 1.1 * the CFM which will provide the sensible Btuh at 50% RH & 75F the sensible load is about .78% sensible * 1.22.

Say, the velocity is 650-fpm the diffuser's Ak is .18-sf of free-air-area; 650 * .18 is 117-CFM.
Temp-drop is 20F * 1.1 is 22 * 117-CFM is 2,574-Btuh sensible * 1.22 is 3,140-Btuh total to the room.

This info does not answer your question but it's info U should know.

Doing a load-calc is extremely important:
Free load-calc
A 5th grader can do these load-calcs - if U can't, find someone that can...
 
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Old 07-30-14, 05:20 AM
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Wall mount evaporators can only throw air about 12 feet well. Any thing over 20 feet I will put two cassettes. A flush ceiling mount will throw air 12 feet each way. It sounds like at 800square feet there should be at least two evaporators. This should save money on operating.
 
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