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Phil
Phil, Mechanical Engineer
Category: Home Improvement
Satisfied Customers: 7580
Experience:  Retired contractor, 51 years experience
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I have a home in Florida. I have 1875 sq ft and very gh

Customer Question

I have a home in Florida. I have 1875 sq ft and very high power bills. I have a 4 ton air/heat system. All appliances are within 5 yrs old and energy star. A new roof, only 1 yr old and continuous $500.00 a month energy bills. Its a older home and I'm frustrated. I have done everything known to man to do and the electric bill is HORRIBLE!
Submitted: 1 year ago.
Category: Home Improvement
Customer: replied 1 year ago.
We have upgraded the wiring and roof last year. We have also had energy mgt come out with duct check and repair. We keep the air unit at 78, and that's too hot! I don't know what else to do!
Expert:  Phil replied 1 year ago.

Hello,

It is quite likely that you can call the air conditioning service company that installed your air conditioning system and ask them the check the refrigerant charge, and they will do that, and then tell you that.... " its perfect per the manufacturers specifications".

Then for example, I could arrive, and notice that there is just 4 or 5 extra ounces, or maybe a pound too much refrigerant in the system...I would remove the extra refrigerant and your electric bill would drop by 30 or 40%... and you would report lower humidity in the home and that the air feels cooler at 78F than it did earlier.

The installer would then assure you that they install systems all over your area and charge them all the same, and he would be correct. Over charging systems and very high utility bills as a result is common.

If you ask such an installer to measure the *suction pressure, and the indoor air temperature at the same time and tell you what the reading is*... he will say that "I charge systems by super heat and sub cooling just like it says on my new $900 electronic refrigeration gauge set"

I always tell them that's wonderful...

It is not possible to argue with a person who owns a $900 refrigeration gauge set, even if he has not read the directions, or noticed that the wrong refrigerant metering device was installed or that one of his duct taped air ducts has fallen of and is blowing your cold air into the attic etc.

If you can somehow tell me what the suction pressure at the outside unit is, and the exact temperature inside the house at the exact same time. I can tell you how badly the system is likely over charged.

You will need a competent HVAC service person to take those readings. That would be the minimum I would need, cubic feet per minute air flow would be helpful as well.

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Other potential and common causes, especially in humid climates is duct work that leaks air... taking the moisture out of the air, to achieve 40%-50% relative humidity in the home is at least half of the cooling system operating cost in Florida.... it is common to see air duct systems that when tested have 10 to 20 air leakage... 20% air leakage in Florida will triple your electric bill... 10% can double your energy costs. 10% air duct leakage is common.

The installer in those cases will tell you that they use only the best duct tape. (he or she will not mention hard cast sealant or sheet metal screws.)

If you ask the installer about this, he or she will say "our duct systems never leak, we test them"... to which you might respond by asking to see the certified air balance tests'... which less than 10% of HVAC contractors will provide, that is because they do not have that testing done.

Those are the two primary factors.

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Other factors: These vary regionally. In many areas the utility company will double or triple the rate you actually pay per kilowatt hour... they do this (legally) by a range of various sur charges if you exceed use limits during peak hours (10 am to 6 pm in many areas)... for instance they may have a very reasonable base rate of 10 cents per KWH, then double that if you exceed the base rate, most homes exceed the base rate.

Terms used are Tiered pricing, time of use pricing, and demand charges.

Then, on top of that, in addition to that doubling of the base rate to be quite clear, there will be a 'peak demand' charge... that can add another 40% to the bill.

The demand charge works this way.

Say you have an electric clothes drier, an electric water heater, an electric stove and of course the AC system running... all electric. That can spike your usage for the time when all are running at once. If the spike lasts longer that 15 minutes, you will have typically 40% added to your electric bill for the next *3 months. That is because the electric company has to stand ready to deliver that peak power at all times... so they charge for that... its called a demand charge.

These are typical of things that can run your electric bill up... I have no idea what your electric utility is charging or not charging and what sorts of appliances you have or if you run them all at the same time etc.... this requires some competent research.

If you call the very competent person screening calls at the utility company or even his or her boss... they will tell you "our base rate is 10 cents a KWH... etc" that of course is accurate..... but not relevant.

If I have not driven you around the bend with all these details please feel free to rate my service so far positively... if you do so, I will be able to afford a longer discussion regarding your particular situation and how to handle it.

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