$900 Electric Bill?!
I am going to be brief, because I have a lot of information to pass along. Bear with me.
4216sf 1 story home built 2 years ago (I am the builder)
Bio-base foam insulation throughout
Unvented, conditioned attic space (insulation on underside of roof deck)
Vinyl low-e windows, insulated doors, etc.
Two (2) 5-ton Amana Heat Pump units
Programmable T-stats set on 82 during the day, 74 overnight
Last month's bill - $688 (approx. 3900 KWH)
Prior month's bill - $461 (approx. 3000 KWH)
Two April Aire dehumidifiers
High bill - generally August / September - $900 +/- $50
No pool, no outbuildings, CF bulbs everywhere, on-demand water heaters
Recently had an energy audit performed. Was told I had one of the tightest houses they'd ever measured in the Houston area; somewhere in the neighborhood of 14% leakage. I went through the house with them with the FLIR camera; no hotspots. Duct leakage on the order of 10% on each system, but it's leaking into conditioned attic space, so I figure that's a wash. Basically beat the pants off the local Energy-Star homes.
Only thing we could figure is the HVAC system is WAY oversized. I had an analysis done prior to building the home, gave to the A/C contractor, they used it for toilet paper or something. I have since gone back and found that analysis and deciphered it, and it appears to show that I need 6.5 tons MAX. I purchased HVAC Calc prior to building, and spent a long time inputting all the correct information. It said I needed something like 4 tons total.
Unfortunately, I caved to the contractor at build-time, assuming he knew more than I did (mistake, apparently). So now, I can't keep the house dry (60% RH or higher, with two dehumidifiers running full-blast), the units short-cycle all day and night, and my utility bills are freaking ridiculous. We are about to pull the trigger on two new 3-ton units (or maybe two 2.5-ton units), and my question is this:
Where can I get some kind of idea what kind of energy savings I can expect? I mean, if two 5-ton 13-seer units are, say, $500/month, what are two 3-ton 14-seer units going to cost? Or two 3-ton 16-seer units? I've googled this, but I can't find a calculator that does what I want.
you might want to try the ARI website at http://www.ari.org
It might not give you exactly what your looking for but will give you a estimate. You can choose from most every manuf. and most any model...
whaaaaa, you let all the smoke out
Dude, you were hosed.
There are several Houston area contractors on this board.
One of them may be able to get you fixed up right.
If you tell me how much your utility company charges per kilowatt. What type of unit you are intrested in (brand name, seer rating etc) I can tell you what it will cost to operate per month, under normal operating conditions for your area.
Originally Posted by adt2
That is a pretty good temperature reset span...
10 tons on that home??What were they thinking??
Are you sure you don't have other issues?
Located where,kws used,and electric rates??
Last edited by dash; 07-09-2008 at 11:20 AM.
The funny thing is that even if you use the "rule of thumb" method of sizing. It's still 2 tons too big. What was the guy thinking?
Well, let me tell you a story -
I used to live in Houston.
I now live in a 3900 square foot house in southern NJ. South Jersey has about 1/2 or 2/3 of a Houston Summer every year.
I have six tons of AC in my house (three up and three down) and my bill last month was $364. AND . . . . due to extensive envelope modifications - my two systems are Grossly oversized and endlessly short cycling.
In the near future I will have four tons total (two up and two down) and I expect to get my electric bill to be somewhere near to $200. by so doing.
The conventional view serves to protect us from the painful job of thinking.
Answers to a few questions:
Magnolia (about 40 miles north of Houston)
Most recent utility bill was 17.1 cents/kwh
Approximately 3900 kwh used
I am probably going to go back with Amana Heat Pump units. Same vendor as original work, but under new management. They seem genuinely interested in making things right. He's offered to let me buy the equipment from his distributor at his cost, and offered to install it at no charge, all with new equipment and labor warranties. I don't get the impression that he's trying to hose me.
Mainly I just want the system to work correctly, cool + dehumidify, and not cost me an arm and a leg.
I think I would have someone verify that the heat strips are not on when the a/c is on or just on period.
Humid Climate - Never Oversize A/c Equipment
To me, that is unbelievable.
4216sf 1 story home built 2 years ago.
Last month's bill - $688 (approx. 3900 KWH)
You have to believe in your heat-gain calc.
Where there is a fair SIZED humidity load, I would rather have my A/Cs a little undersized, & NEVER oversized.
I would make the NECESSARY CHANGES & figure out a way to recoup, as much as possible, the oversized equipment costs.
When you replace that equipment, be extra careful that you do not replace it with yet oversized equipment!
I have an old 1937 average insulated all electric farm home, except for oil heat, I cool it all through the summer for an average $40.00 to $45.00 dollar a month electric bill. View my farm home & read how it is done.
A half-ton 9.7-EER room A/C cools the entire first floor, just under a HALF-TON 7-EER COOLS UPSTAIRS bedroom, hallway, stairwell & bathroom; yes, it is true; under a Ton of total cooling.
The oil heating in the winter is my big expense!
- Darrell - HVAC RETIRED
I would consider higher efficiency 2 stg units and take advantage of the dehumidify options to try and reduce the runtimes of the installed dehumidifiers during your peak cooling season. I think the A/C's will operate more economically when sized and installed properly.
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Stupid question: What is a heat strip, and how would I verify whether or not it's on?