Air Conditioning - A/C unit appears to have caused a BIG jump in electricity usage

:confused: This year's a/c season has come to a close in N. Va. and I have become concerned about a 45% increase in my electric utilty bill over the May-Sep billings last year :mad: - even though the cooling season this year and last year were very simliar in temp and humidity here and we have not added any new electrical devices that eat power during the period. The power company has checked the meter and suggests the culprit is likely the a/c unit (Trane) (which is 17 years old but was a highly energy eff. unit at the time of installation). My a/c contractor has checked out the unit and it apparently functions pretty well (it seemed to work fine during the cooling season-but I occasionally noticed that the lights in the house would dim on startup). He did say that on startup, unit is drawing 100 amps which is about double what they would expect to see, he suggested installing a 'hard start' modification but could not answer whether or not this situation was what might have driven up the electric consumption. Any experts out there have an opinion or an answer to what might have caused our 5 month consumption to go from May-Sep 8500 to 12900 kwh from '03 to '04 & whether we would be better off replacing the unit rather than adding the modification suggested?

100 amp on start dont sound good at all. 17 years old, life on most is 15 years.With all the above Id go for a new AC unit for sure. Not just a start kit .Your AC could have a seer of 8 or ten the new ones go for like a seer on up to 19.50. Your coil can have dirt in it. Did you check on all the wire lugs at the unit and in the home panel,are they all tight.


ED ;)

sounds like the compressor is on its last leg. i am with ed, replace it with a much more efficient unit. you will see a lot of savings with just a 10 seer over what you have.

Maybe the crankcase heater is stuck on ALL the time. Did anyone check for that??

Did your usage go up or just your bill? Many places saw a significant rise in electric rates this year. Otherwise, I'm with Ed. You're at end of life. A new system would probably pay for itself very quickly, especially if you're about to incur a repair bill for the existing system. 17 years ago high efficiency was no more the 12 SEER. Today you can get over 19. 19 SEER uses around 50% less energy than 12 SEER. I would expect rates to rise significantly again next year...

Doug M.

I'm with Ed and HVAC in the fact that it just started dimming the lights I'd like to know what the running amps are compaired to what they should be.

The hard start would only help the utility bill if you were being charged for demand but you are actually seeing and increase in usage.

What fuel do you use for heating? I've also seen where a unit utilizing an electric heat package can have the heaters energized during cooling mode.

mattison -- heating is natural gas
dougm -- billing went up @ 55%, the usage of kwh's was what kicked off my concerns - that was the 45% figure I cited in my posting.
jughead -- are you pulling my leg -- never heard of a crankcase heater in a residential HVAC system -- then again I am not 'edge-E-ma-cated' in the ways of HVAC systems :eek:
hvac4u & Ed -- your comments re-inforced my gut feeling that the time has come to bite the bullet and replace the system. I have had only one service call in 17 years and that amounted to about $150 -- and the electric bills for our 3100 sq ft home have been less than we had in a 1600 sq ft home we owned previously -- the seer on the unit in question was 12, so I guess my prior savings will be invested in a new 19 SEER unit.

Now the next question -- does ac replacement include the coils (?) that sit above the furnace unit inside the house or is it typically only the exterior unit with the compressor, etc.

Well you can rule out the electric heater being stuck on. Jugs refrence to the crankcase heater is valid in a way. Lots of residential units have them but they are energized all the time so that would not have shown you an increase.

When you decide to do the change out you will want to change out the indoor coil with the outdoor section, possibly the line sets too. Get several bids for the job and have them do a load calculation on paper for you. If they claim they don't need one don't even consider using them.

Yes for sure you want a new inside coil to match the outdoor unit.
lots and lots of outdoor compressor's have a crankcase heater on them. This will keep the oil warm so Freon wont get in to it and slug out the compressor. Like if you had a unit that had one on it. They will tell you to turn the 220V power on to it for 24 hr, BEFORE you turn on the AC.After that it stays on if the AC is running or not.


ED ;)

I'm used to working on 100 and 200 ton A/C units. I didn't know that small units heaters are on all the time. It's been several years since I've worked on smaller units other than mine at home. See, everyone learns something here.

When I 1st started out I found out the hard way about the crankcase heater being energized all the time. The unit in question was for a kitchen in a nursing home. The contactor had went bad and it was the one with only 1 leed that opens and closes. I had a double throw on my truck and replaced it with that. Needless to say they used the single throw so that the crankcase heater would always be energized. It about killed that poor thing starting up like that when it got cold out.