Comparison of the long term cost of Open Circuit vs. Closed

[Dmitchell]

Getting back to the discussion of the cost of trimix fills, I sat down and created the attached spreadsheet to compare the two. It was interesting what I found. Yes, CCR is more expensive but not as much as you might think.

Here's what I did, I hypothetically created 2 new but avid divers, Start them at Basic Openwater, run them through Rescue Diver then then start the "Tech series". One diver stays OC all the way and one eventually moves to a rebreather. Then they both train to the level of normoxic trimix. Over the course of 5 hypothetical years and 460 dives I've compared how much each has invested in diving.

Some points to clarify:

My OC guy has standard tech gear and uses his original OC computer in gauge mode for tech dives. The numbers get really interesting if the OC guy buys a Wiz-Bang $1500-2,000 computer. He owns 2 sets of double 100's. (it was mentioned previously about someone having 5 sets) Tech dives are based on filling the 100's with trimix for 200' dives and topping them for a lighter mix and using that for the subsequent 150' dives. So the OC guy is able to get a 2nd trimix dive for the cost of an airfill ($5.00). I also assume that deco bottles are usable for 2 dives. I also assume that a set of doubles counts as a single fill for air or nitrox. That's how I do it at my store - one fill whip=1 fill regardless of size.

The CCR guy buys a KISS Classic; it's not the most expensive rebreather on the market but it was easy to price out and is perfectly suited for the types of dives that these guys are doing. The CCR guy keeps his OC Singles wing for the rebreather and does sell his Steel 100's once he's converted. He also converts his OC reg to a deco reg. I figure Sorb at about $5.00 per hour. The KISS has about a 3 hour scrubber duration. Most divers will dump the remaining sorb at the end of a day so I figure 20% waste there. My OC guy has the KISS with a Shearwater computer and his original OC Computer in Gauge mode. Ideally he would rotate his cells so that he replaces one every 4-6 months but for simplicity in the math, he changes them all each year.

All my numbers are off the top of my head and assume that everything purchased is at full MSRP pricing. I tried to be as accurate as possible on both sides of the coin as I plan to use this in my classes to show my tech students a comparison of the costs. I know there are a gazillion scenarios but I was trying to create a logical one.

I tried uploading to this post but apparently no xls, doc or pdf files are allowed so here's a link
Dave

[scottsax]

I gotta say, that is really compelling reading! I think the year 5 costs are the most telling. The long term operating costs of CCR vs OC for technical diving is a strong argument for moving toward a rebreather, although the initial investment is daunting, to say the least.

Nice work!

[Burntchef]

nice job dave, maybe one day i will use it as a presentation to my girlfriend to show her the savings

[Sounder]

nice job dave, maybe one day i will use it as a presentation to my girlfriend to show her the savings

This is justice. Justice for all the times the wife comes home with a bunch of bags and the first thing out of her mouth is "you're not going to believe how much I just SAVED!!"

[CaptnJack]

The CCR guy needs more than 1 Al40 to bailout from 200ft no? (or did I miss it?)

The other thing you missed is that the OC guy borrows and shares gear like crazy when his buddies come up for So/MoCal. And gets to borrow their spare sets of doubles when he goes there. I don't think there's a cost there, just a benefit.

[camerone]

The CCR guy needs more than 1 Al40 to bailout from 200ft no? (or did I miss it?)

You do 200' CCR with a 40 of bottom mix and a 19 of O2 (depending on the dive profile, it'd be fine) or just use a single AL80 instead of the 40. The price difference is insignificant so the numbers don't change.

[Dmitchell]

The CCR guy needs more than 1 Al40 to bailout from 200ft no? (or did I miss it?)

My intent was line where both of them bought an AL80 at some point. I had it in my head but missed that line. It's a wash as far as cost since they both buy them. I factored it in on the cost of visuals, etc just not the purchase of the tanks.

For a 200'+ dive I usually carry an 80 (bottom mix) and a 40 (60% or richer).

DM

[Burntchef]

pretty cheap helium dave, i pay a $1.10 a cf. your o2 is a bit cheaper as well. please mail me 200cf of 25/25.