SEER = Btu per dollar. 1-kW of electric with your old system produced 7,000 Btu of cooling. The new system produces 14,000 Btu per kW. Everything is based upon the condenser and coil being a matched set.

"SEER = Btu per dollar. 1-kW of electric with your old system produced 7,000 Btu of cooling. The new system produces 14,000 Btu per kW."

- This statement is incorrect. You are confusing Energy Efficiency Ratio (EER) with Seasonal Energy Efficiency Ratio. SEER and EER are calculated at different outside temperatures. EER is calculated at 95 degrees and SEER is calculated in the low 80s. At higher outside temperatures, SEER is a meaningless number.

In your example, the Energy Efficiency Ratio would be 7 (7000 btu-hr / 1000 watts). The SEER would be higher than 7. In my opinion, SEER is BS.

Garyg,

Are you able to separate out the usage for HVAC only? Do you have a baseline(non-HVAC)usage number?

Without checking the power factor, current draw is not a reliable indication of dissipated power.

What did you pay for the same period last year? How many kWh?

SR

Even if you had the AC on its' own meter you would need an extremely involved math equation BTUH heat-load index to illustrate a somewhat meaningful comparison.

Additionally, as the 82-F outdoor temp rating of the 14-SEER will see that SEER lowered as compared to the old 7-SEER at 95 to 105 temp levels. Comare the EER Ratings taken at 95-F OD ambient not the SEER ratings at 82-F.

I have a 7 EER 5,950-BTUH window unit upstairs & now a 9.7 EER 6,000-BTUH on the ground level floor with a cool basement.

Years before that I had the upstaits unit downstairs & could see very little difference in their cooling performance & electrical use.

How would their EER Ratings compare at say 100-F?

I do like the Goodman 14-SEER AC condensers' with a Copeland Scroll compressor & a TXV metering device, two in the case of a heatpump. udarrell _ 2007

JDB:
I cannot separate HVAC usage versus all other electric usage.

Brickeye:
If I assume that the power factor is the same for both units at all times, it is a wash. I'm not sure how else to handle this. Is power factor typically .9? I'm looking at ballpark numbers for cost savings.

fsq4cw:
In July of '06, I used 1056 kw for a bill of $240 (the high electric rates went into effect in '06). Last July was hotter than this July with the avg temp listed on the '06 bill at 80 degrees versus 77 degrees on this bill. Last July also had one additional billing day. I would have to do a degree-day comparison for an accurate assessment. To confuse matters, I also switched electric suppliers in Feb '07 and locked in a 1 year supply rate of 9.8 cents/kw-hr generation. Current rates with old supplier are 11.4 cents/kw-hr generation (as were the rates in '06). I should have locked in the 2 year rate of 10.4 cents, but hind sight is always 20/20.

Darrell:
The new Goodman has a 12 EER. Not sure about the old Trane.

Power factor is unlikely to be the same for older and newer equipment.
Poor power factor has become enough of a problem that correction has been required on some new equipment (mostly ballasts).
Few induction motors under load can hit 0.9 without some correction circuitry, and the factor even varies with motor load.

Brickeye:

Does power factor make that much of a difference in residential a/c for calculating my costs?

Can't I just use (Amps x Volts)/1000 x Price ($/kw-hr)= $/hour? How much will I be off if I don't include the power factor?

Thanx.

pf = 0.8 for most inductive loads. It's generally on the motor nameplate, though it's not required to be.

However, I don't believe that most (if any) kWh meters can tell the difference between reactive power and resistive power. You pay for total power, reactive and resistive, so for the basis of calculating your cost in a residential (i.e., not 3-phase) application, I believe your formula is correct.

Like Brick said, deteriorating pf has been a problem for some time now, and I know virtually every commercial and industrial facility in the country has a reactive load meter, and they pay for reactive load. It's one way to encourage them to design their systems to reduce reactive load, such as by adding capacitor banks or using synchronous motors. I believe residential meters are the same.

Reactive load is a problem for utilities because it creates circulating currents that go back and forth between the generator and the load, doing no work but heating up transmission and distribution lines, reducing the maximum real power they can carry. The industry has tried using power conditioners at the transmission level to reduce the circulating currents associated with reactive load, with some spectacular and extremely expensive failures (HUGE explosions destroying facilities costing more than $100 million). They now are instead encouraging customers to reduce their own reactive load through financial incentives.

Probably more than you wanted to know.

"I don't believe that most (if any) kWh meters can tell the difference between reactive power and resistive power."

Absolutely wrong.
A standard watt-hour meter ONLY measures actual power.
Only the in-phase voltage and current produce a torque on the rotor.
This is what makes designing the electronic meters so hard.
Large commercial services have the power factor measured and then pay a rate based on the power factor and the peak usage.
Many utilities will even allow a backup generator to be used during the measurement of power demand if the generator can be placed under POCO control to be turned on as part of load control.

Matt:

Thanx for answering my question and educating me on power factor - much appreciated.

No problem, gary.

Brick: ALL commercial and industrial meters here in CA measure and charge for reactive power (VAR) as well as resistive. I checked this morning and confirmed that you are right in that residential customers are not charged (neither were commercial until recently), though I've heard the new residential meters being installed by some smaller utilities have the flexibility to measure only reactive power (as well as do time-of-use metering, etc.).

And there are NO standby generators here under the control of any POCO, thanks to very strict air emissions regulation. We'd rather let the lights go out than emit even one extra pound of NOx, apparently. So, industrial customers are not allowed to run their generators except during outages and periodic tests.

In my opinion, SEER Payback is NOT being Properly Represented to the Consumers at their normal operating conditions in their climate zones!
The SEER ratings are too nebulous & do not translate to the specific application conditions that each consumer will normally have. EER is simpler & more reliable when the systems are correctly sized to the load.

The SEER of a system is determined by multiplying the steady state energy efficiency ratio (EER) measured at conditions of 82°F outdoor temperature, 80°F dB and 67°F wB indoor entering air temperature by the Part Load Factor (PLF) of the system. (The PLF is supplied by the government.)

Consider, 82-OD 80-ID 50% RH, that is only a 2 degree difference, additionally, at that outside temp we normally do not operate our ACs.

You can do a search for my other posts concerning this important issue to consumers. (udarrell SEER)

There are several climate zones where we need larger compressors to coil areas. These are climate that are very hot & tose that are extremely humid.

The smaller Btuh compressor to coil ratio is NOT design to achieeve optimal results in those conditions.

Add to that, Bob Brown who is from Texas stated that: "in new construction Texas Mandated only one (1) Ton of cooling for 750sf of floor area."

The least they could do is allow the contractors to use the smaller compressor's tonnage rating for the required 750-sf of floor area. which is less than the matched coil combinations supposedly deliver at their top Rated Conditions.

Always ask proof of what the EER combination Rating is of the condenser & E-Coil, & also the compressor's Btuh.

In most climate zones I would not go above "the 82-F/80-F Rated" 15-SEER which is - (in this case, in tough heavy humidity load conditions, "nearly meaningless") - the energy star level. Actually, a 14-SEER is my personal top pick.

I would also always want a TXV metering device & a Copeland Scroll compressor. udarrell _ 2007

Here is a link that might be useful: udarrell.com

Ballpark maximum cost-per-hour to run new 14 SEER (12 EER) Goodman unit is:

(16.4 amps total) x (220 volts) x (.122 $/kw-hr total price) / 1000 = $.44 per hour = 44 cents/hour.

Not bad considering a 65% rise in the electricity rate.

I do indeed have 2 TXV metering devices (1 on the air handler and 1 on the outside unit) and a Copeland scroll compressor.