Buying a compressor to save money
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From Seattles power website, $0.14/kwh for the second block of power.
Compressors as a rule are 1hp/cfm which is roughly 1kw so give or take on power you are at $0.14/60cf for power so call it $0.20/AL80 for easy math.
Filters and oil are roughly speaker $1/fill each, again conservative rough numbers.
Up front cost is $5k give or take then add about a grand in for a remote intake filter *the best way to quiet these things down*, whips, and whatever else so call it $6k and you amortize it over 5 years so $1200/year and say you do 100 dives a year, so $12/fill for the pump and we can consider that a fixed cost regardless of whether you are filling a HP130 from empty or a mostly full AL80 since I assume your dive shop charges a fixed rate for fills as most outside of cave country do. This is also obviously assuming that the pump is brand new and has no residual value after 5 years and must be replaced, and since they will easily go much more than that, you then have to start adding in rebuild costs and what not so I tend to just leave it at 5 years and it's dead for conservative math.
Grand total is about $15/fill ish for an AL80 assuming they are close to empty when you fill them. That doesn't include any cascade bottles if you go down that route, adding in electrical capacity to your garage, etc, but it's a reasonable number. The number is somewhat variable in the cost of power/consumables so while the $12 is considered a fixed cost, the balance ends up being ~$0.04/cf depending on the quantity of gas you end up moving during the year so the number is either slightly higher or lower than that but it's a good number.
You have $10+tax so call it $11, you have to make up the $4/fill in either time/gas savings or in the convenience factor of being able to fill mostly wherever you want. You can massage the numbers of the fixed costs of the pump as much as you want to make the math work in your favor or not, but the ~$0.04/cf is a pretty solid number to use.
Compressors as a rule are 1hp/cfm which is roughly 1kw so give or take on power you are at $0.14/60cf for power so call it $0.20/AL80 for easy math.
Filters and oil are roughly speaker $1/fill each, again conservative rough numbers.
Up front cost is $5k give or take then add about a grand in for a remote intake filter *the best way to quiet these things down*, whips, and whatever else so call it $6k and you amortize it over 5 years so $1200/year and say you do 100 dives a year, so $12/fill for the pump and we can consider that a fixed cost regardless of whether you are filling a HP130 from empty or a mostly full AL80 since I assume your dive shop charges a fixed rate for fills as most outside of cave country do. This is also obviously assuming that the pump is brand new and has no residual value after 5 years and must be replaced, and since they will easily go much more than that, you then have to start adding in rebuild costs and what not so I tend to just leave it at 5 years and it's dead for conservative math.
Grand total is about $15/fill ish for an AL80 assuming they are close to empty when you fill them. That doesn't include any cascade bottles if you go down that route, adding in electrical capacity to your garage, etc, but it's a reasonable number. The number is somewhat variable in the cost of power/consumables so while the $12 is considered a fixed cost, the balance ends up being ~$0.04/cf depending on the quantity of gas you end up moving during the year so the number is either slightly higher or lower than that but it's a good number.
You have $10+tax so call it $11, you have to make up the $4/fill in either time/gas savings or in the convenience factor of being able to fill mostly wherever you want. You can massage the numbers of the fixed costs of the pump as much as you want to make the math work in your favor or not, but the ~$0.04/cf is a pretty solid number to use.
100days-a-year
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I never came close to the numbers you guys are talking about. Maybe doing more tanks per year brings the unit cost per tank down.
Oxygen was my biggest expense if you factor in time to run to and from Airgas or Praxair to switch out Ts.
I saw a couple of membranes on commercial boats and that would seem ideal.
Oxygen was my biggest expense if you factor in time to run to and from Airgas or Praxair to switch out Ts.
I saw a couple of membranes on commercial boats and that would seem ideal.
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Invacare home fill for reasonably small volumes. Can find them used for a grand and you have unlimited 2000psi O2. Not fast but a ton of it
As stated, you'll never save. Not just because of ongoing costs, but because it will never be enough and you'll keep throwing money into it. My initial reasoning for wanting a compressor is I live 2 hours from the dive sites I frequent, so I just drive up for the day to dive. If at the end of the day I had to get fills then drive home, it would be pretty late. It got tiring. Trying to get fills at my local dive shop was a joke. Doubles were $30-40 a pop and usually underfilled or off by multiple %. So originally I wanted a Bauer Jr. Then I realized it wouldn't be enough, so I got a used K14. That was great for a while, but then I needed a booster too. Then I decided I needed to start vipping and cleaning all of my tanks, so I bought all of the gear necessary for that including a tank tumbler. What I didn't know is that because I'm filling my own tanks, they're always spotless. My tanks always needed to be tumbled previously because of the crap gas the local dive shops near me were pumping. So all of the tumbling equipment sits unused. Then I decided I needed bank bottles. God only knows what's next.
Point is, buy a setup if you think you'll enjoy it and it makes life convenient. Expect to spend twice your initial budget. I really enjoy forgetting all of my problems by walking out into my garage and filling tanks and working on dive gear. I estimate I'm in the $18-20k range with everything I've purchased (that's a very conservative number cause the real numbers are scary). Luckily I bought more compressor than I needed from the get-go or I would have had to buy twice.
Point is, buy a setup if you think you'll enjoy it and it makes life convenient. Expect to spend twice your initial budget. I really enjoy forgetting all of my problems by walking out into my garage and filling tanks and working on dive gear. I estimate I'm in the $18-20k range with everything I've purchased (that's a very conservative number cause the real numbers are scary). Luckily I bought more compressor than I needed from the get-go or I would have had to buy twice.
In about six years, my wife and I will have the option to travel for an extended time. I thought for sure I should buy a compressor for the trailer that will haul our SCUBA kit (plus my track and touring bikes).
I mulled it over and concluded I prefer to buy several HP tanks for each of us, fill them all at a LDS, dive for a week and then go find another shop for the next fill.
Visiting the LDS will give us something to do, people to meet and local insight to be gleaned. I figure the visits to the dive shop will also decrease the amount of time my wife and I sit in the RV arguing over stuff like why she can’t run the compressor and why I can’t change the cat litter.
I mulled it over and concluded I prefer to buy several HP tanks for each of us, fill them all at a LDS, dive for a week and then go find another shop for the next fill.
Visiting the LDS will give us something to do, people to meet and local insight to be gleaned. I figure the visits to the dive shop will also decrease the amount of time my wife and I sit in the RV arguing over stuff like why she can’t run the compressor and why I can’t change the cat litter.
100days-a-year
Contributor
For the volume I'd need to bank them but still better than shlepping 500 pounds of Ts around every week.
Years ago I decided to put a value on my time and take it into consideration when planning expenses. I ain't cheap so driving around time could be better spent elsewhere.
Still Kicking
Contributor
The value of a compressor rarely, if ever, equates to dollars and cents. Even busy dive shops are elated if their compressor costs break even.
It really has to be measured in terms of convenience and that is a personal evaulation made by the owner.
It really has to be measured in terms of convenience and that is a personal evaulation made by the owner.
A while ago I was thinking to purchase a Rix SA-6 Diesel and a couple of old-school steel 72's to take with when traveling around in a van or small RV, off-gridding. I still like this idea...
rx7diver
captain
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