I will try to find the spreadsheet I put together with cost estimates but the reality is I did not get into this to save money. Some of this might be too much information but I am writing it down here incase I forgot or someone else asks. I'm sure I messed up some estimates here but I will try to correct it if I find errors.
Based on hours I pump about 13,000cu/ft of nitrox 32 a year through my compressor with a blending stick. Not a whole lot compared to most commercial dive shops but pretty good for my wife and I. I almost never pump air as almost all of my local diving is on a rebreather or 32%. This is based on my hours meter on my compressor and the written log I use to keep track of filter/oil changes/maintenance log.
Very rough napkin math. 13,000cu/ft / 200cuft (double 100s/85s) = 65 doubles fills (or 130 single tank fills at 100cuft). This is not perfect as I also fill HP120s or AL80 stages but 90% of the time I dive HP100s/LP85 doubles if I am not on a rebreather. It's just a rough estimate based on last 5 years.
The cheapest "local" dive shop (realistically hour away from me in normal Boston traffic) charges $16 for a nitrox fill.
130 fills x 16$ = $2080 rough estimate of what my fills would cost.
If I had to go to the dive shop then I'd spent about $2k in fills, not including the colossal waste of time sitting in traffic and the cost of putting gas into my truck, wear and tear on my truck, moving tanks in and out of my garage/shed. The stress of fighting Boston traffic because of students, Cape Cod vacationers, or whatever random event/concert that happens to be going on is not worth it to my sanity.
The irony here is there are 2 dive shops within 15-20 minutes from my house. They are strictly air only. They have absolutely zero interest in nitrox. If they banked 32% I probably would have never bought a compressor.
Filters
I put about ~60-75 hours on my compressor per year. Again, not a whole lot. During this time I go through 3-4 x X22629 (P21-type) filters cartridges and 2 x X65240 filter cartridges.
According to Filtertechs, a X65240 will process ~10,000 cu/ft. of air as long as the air inlet temperature going into the filter tower is 80F (~27c). The reality is I am filling in hot and humid New England summers so I probably get about 70% of that. So let's call it 7,000cu/ft. I change this filter out every 30-40 hours.
I typically change the P21 triplex type cartridges out around ~15-20 hours, closer to 15 hours in the summer. The reality is I probably should change these more frequently but because I have both filters stacks together I don't worry about it too much.
I could save some money here and repack my own filters but I don't really care that much. I'd rather buy third-party filters from Filtertechs.
4 x X22629 x $40/per filter = $160
2 x X65240 x $60/per filter $120
-----
$280 a year on filters.
Oil
I spent $115 on a 1 gallon (3785ml) of compressor oil. It uses Anderol 750. My compressor takes 550ml of oil. The manual says to change the oil every 100 hours however I do mine every year or 75 hours to be conservative. There is enough in 1 gallon to do ~6 oil changes with some extra. So let's say each oil change cost me ~$20 dollars.
Oxygen
I pay $32 for a T of oxygen (300cu/ft. My yearly bottle lease fees are $65/year for cylinder rentals. This somewhat expensive compared to most high volume gas suppliers but honestly it doesnt bother me since my gas supplier doesnt ask me any questions about what I am using it for. We don't talk about scuba.
Based on ~300cu/ft of T of oxygen and 100cu/ft tanks. I get about ~24 fills of nitrox 32% per T bottle. With a nitrox stick I can effectively drain T bottles down to nothing. There is no wasted gas being returned.
130 nitrox fills / 24 = 6 T bottles of oxygen required for 130 fills at 100cuft/each.
I always keep 3 T bottles on hand since I also need to fill rebreather bottles so let's calculate my lease fees at 65 x 3 = $195/year. 6 T bottles x 32 = $192. There are some random hazmat fees and taxes but I pick the bottles up myself so there is no delivery charge.
$387 in T bottles of oxygen and lease fees. I did not include helium or my other oxygen usage for rebreather bottles here. The reality is I definitely spend more than that since I also get helium and go through more oxygen for rebreather and deco bottle fills.
Air Testing
I test my gas bi-annually (twice a year). Each test is about $100 so I spend $200 on gas testing.
Electric
Massachusetts is around 0.25 cents per kilowatt-hour (kWh) which is pretty expensive.
220V×18A=3960W=3.96kW
3.96kW×75h=297kWh
~300kWh×0.25 USD/kWh=75 USD
So let's call it $75/year in electric.
So we're at $280 in filters, $20 in oil, $387 in oxygen, $200 air testing and $75 in electric. = $962 yearly operating costs. Did I miss anything else?
Let's round up and say my yearly operating costs are $1000/year.
Compressor + Fill Panel (Estimated Costs)
Alkin W31 - $3,400 (I believe they are closer to $4000-$4500 now)
Secondary Filter Stack + Priority Valve (PMV) + Check valves + Hoses/Fittings - $1000
5 Port Manifold - SPG - Hose/Fittings/Valves - Additional Fill Whips - $1000
Nitrox Stick + Welding Regular + O2 analyzer + Dwyer flow meter - $400
Mounting Hardware / Brackets / Plywood - $100
-----------------------------------------------------------
$5900. So I am going to say I have about $6k invested in my compressor and fill panel. This is a really small setup. You could spend a lot more if you wanted a bigger compressor or you could also get lucky and buy something used for cheap.
I am probably forgetting lots of other pieces. I did not include the 2 boosters that I own as it's outside the scope of this discussion. I didn't include in bank / storage bottles because I didnt own any for the first 4 years.
Assuming I would have spent $2000/year on fills at dive shop for my wife and I then it took me about ~3 years to get return on my investment. The reality is it was quicker than that. I built out my fill panel very slowly, upgraded it and tinkered with it a bunch. I wasn't even using a panel with a 5 port manifold, or secondary filter stack for first 18 months I owned the compressor.
Since my compressor is paid for my operating costs are $962/year. We can assume $962 / 130 fills = $7.40/ nitrox fill. Even at 65 fills it would still work out to less than $15/fill. My tank monkey (me) works for beer. If was strictly filling air only I'm under $5/fill.
If I had to do it all over again I'd buy a bigger compressor. I will NEVER not own a compressor. At some point I will upgrade to something in the 5-6cfm range and keep this one as backup. I want to be able to fill banks and the small Alkin is just too painfully slow to do that (although I know some people do it)
Based on hours I pump about 13,000cu/ft of nitrox 32 a year through my compressor with a blending stick. Not a whole lot compared to most commercial dive shops but pretty good for my wife and I. I almost never pump air as almost all of my local diving is on a rebreather or 32%. This is based on my hours meter on my compressor and the written log I use to keep track of filter/oil changes/maintenance log.
Very rough napkin math. 13,000cu/ft / 200cuft (double 100s/85s) = 65 doubles fills (or 130 single tank fills at 100cuft). This is not perfect as I also fill HP120s or AL80 stages but 90% of the time I dive HP100s/LP85 doubles if I am not on a rebreather. It's just a rough estimate based on last 5 years.
The cheapest "local" dive shop (realistically hour away from me in normal Boston traffic) charges $16 for a nitrox fill.
130 fills x 16$ = $2080 rough estimate of what my fills would cost.
If I had to go to the dive shop then I'd spent about $2k in fills, not including the colossal waste of time sitting in traffic and the cost of putting gas into my truck, wear and tear on my truck, moving tanks in and out of my garage/shed. The stress of fighting Boston traffic because of students, Cape Cod vacationers, or whatever random event/concert that happens to be going on is not worth it to my sanity.
The irony here is there are 2 dive shops within 15-20 minutes from my house. They are strictly air only. They have absolutely zero interest in nitrox. If they banked 32% I probably would have never bought a compressor.
Filters
I put about ~60-75 hours on my compressor per year. Again, not a whole lot. During this time I go through 3-4 x X22629 (P21-type) filters cartridges and 2 x X65240 filter cartridges.
According to Filtertechs, a X65240 will process ~10,000 cu/ft. of air as long as the air inlet temperature going into the filter tower is 80F (~27c). The reality is I am filling in hot and humid New England summers so I probably get about 70% of that. So let's call it 7,000cu/ft. I change this filter out every 30-40 hours.
I typically change the P21 triplex type cartridges out around ~15-20 hours, closer to 15 hours in the summer. The reality is I probably should change these more frequently but because I have both filters stacks together I don't worry about it too much.
I could save some money here and repack my own filters but I don't really care that much. I'd rather buy third-party filters from Filtertechs.
4 x X22629 x $40/per filter = $160
2 x X65240 x $60/per filter $120
-----
$280 a year on filters.
Oil
I spent $115 on a 1 gallon (3785ml) of compressor oil. It uses Anderol 750. My compressor takes 550ml of oil. The manual says to change the oil every 100 hours however I do mine every year or 75 hours to be conservative. There is enough in 1 gallon to do ~6 oil changes with some extra. So let's say each oil change cost me ~$20 dollars.
Oxygen
I pay $32 for a T of oxygen (300cu/ft. My yearly bottle lease fees are $65/year for cylinder rentals. This somewhat expensive compared to most high volume gas suppliers but honestly it doesnt bother me since my gas supplier doesnt ask me any questions about what I am using it for. We don't talk about scuba.
Based on ~300cu/ft of T of oxygen and 100cu/ft tanks. I get about ~24 fills of nitrox 32% per T bottle. With a nitrox stick I can effectively drain T bottles down to nothing. There is no wasted gas being returned.
130 nitrox fills / 24 = 6 T bottles of oxygen required for 130 fills at 100cuft/each.
I always keep 3 T bottles on hand since I also need to fill rebreather bottles so let's calculate my lease fees at 65 x 3 = $195/year. 6 T bottles x 32 = $192. There are some random hazmat fees and taxes but I pick the bottles up myself so there is no delivery charge.
$387 in T bottles of oxygen and lease fees. I did not include helium or my other oxygen usage for rebreather bottles here. The reality is I definitely spend more than that since I also get helium and go through more oxygen for rebreather and deco bottle fills.
Air Testing
I test my gas bi-annually (twice a year). Each test is about $100 so I spend $200 on gas testing.
Electric
Massachusetts is around 0.25 cents per kilowatt-hour (kWh) which is pretty expensive.
220V×18A=3960W=3.96kW
3.96kW×75h=297kWh
~300kWh×0.25 USD/kWh=75 USD
So let's call it $75/year in electric.
So we're at $280 in filters, $20 in oil, $387 in oxygen, $200 air testing and $75 in electric. = $962 yearly operating costs. Did I miss anything else?
Let's round up and say my yearly operating costs are $1000/year.
Compressor + Fill Panel (Estimated Costs)
Alkin W31 - $3,400 (I believe they are closer to $4000-$4500 now)
Secondary Filter Stack + Priority Valve (PMV) + Check valves + Hoses/Fittings - $1000
5 Port Manifold - SPG - Hose/Fittings/Valves - Additional Fill Whips - $1000
Nitrox Stick + Welding Regular + O2 analyzer + Dwyer flow meter - $400
Mounting Hardware / Brackets / Plywood - $100
-----------------------------------------------------------
$5900. So I am going to say I have about $6k invested in my compressor and fill panel. This is a really small setup. You could spend a lot more if you wanted a bigger compressor or you could also get lucky and buy something used for cheap.
I am probably forgetting lots of other pieces. I did not include the 2 boosters that I own as it's outside the scope of this discussion. I didn't include in bank / storage bottles because I didnt own any for the first 4 years.
Assuming I would have spent $2000/year on fills at dive shop for my wife and I then it took me about ~3 years to get return on my investment. The reality is it was quicker than that. I built out my fill panel very slowly, upgraded it and tinkered with it a bunch. I wasn't even using a panel with a 5 port manifold, or secondary filter stack for first 18 months I owned the compressor.
Since my compressor is paid for my operating costs are $962/year. We can assume $962 / 130 fills = $7.40/ nitrox fill. Even at 65 fills it would still work out to less than $15/fill. My tank monkey (me) works for beer. If was strictly filling air only I'm under $5/fill.
If I had to do it all over again I'd buy a bigger compressor. I will NEVER not own a compressor. At some point I will upgrade to something in the 5-6cfm range and keep this one as backup. I want to be able to fill banks and the small Alkin is just too painfully slow to do that (although I know some people do it)
