Kinder Morgan (KMI 0.15%) and Kinder Morgan Energy Partners (NYSE: KMP) report earnings on Wednesday after the market close. Here are three things investors should keep an eye on.

1. Natural gas pipelines unit
The natural gas segment is Kinder Morgan's biggest moneymaker, making the health of this beast crucial to the overall health of the partnership. In the past, soaring volumes from the Eagle Ford Shale have provided a big earnings boost, but what investors may want to watch closely are the volumes from natural gas used in power generation.

A year ago, the Tennessee Gas Pipeline dropdown boosted earnings for the segment, in part thanks to a 12% increase in throughput for natural gas power generation. The system proved vulnerable to fluctuations in that market in 2013, however, and given that the Energy Information Administration has reported that the levels of natural gas used for power generation remained below 2012's levels virtually all year, TGP may not provide the same huge boost that it did a year ago.

Again, it is still the largest earning segment, but it remains important to watch weakness here. Last quarter overall segment transport volumes were down 6% year over year because of weak demand in the power generation market, indicating the significance that this market plays in the segment.

2. CO2 unit 
In the partnership's "2014 Financial Expectations" release last month, CEO Rich Kinder made reference to increasing demand for carbon dioxide, which means this segment could be a bigger winner going forward than some expected. In the partnership's third-quarter release, management indicated it expected this segment to outperform its budgeted growth of 5% by year-end. The fourth-quarter results for this segment will let us know not only whether the segment actually surpassed its budget, but they should also give us an indication of what sort of growth management expects going forward.

Another thing to keep an eye on here, not just for the fourth quarter but all of 2014, is commodity risk. The partnership hedges most of its oil production in this segment, but it remains exposed when it comes to its volumes of natural gas liquids. Though prices of propane and butane are slowly ticking upwards, ethane is nearly worthless, and may remain so for years to come. That said, any future strengthening of NGL prices should have a very positive effect on this segment.

3. Distribution coverage ratio
All year, we've heard that Kinder Morgan Energy Partners would achieve full-year coverage greater than or equal to 1.0 times distributions. The cyclicality of the business means falling short in the second and third quarters, while providing ample coverage in the first and fourth quarters. Well, here we are. Kinder Morgan will either achieve an adequate coverage level for the year or not.

Bottom line
As far as returns go, Kinder Morgan did not have a great 2013 and investors will be looking for signs of positive momentum on Wednesday. You can catch the partnership's webcast here at 4:30 p.m. EST.