5 lb vs 10 lb vs 20 lb CO2 tank for a home kegerator: which size to actually buy

For most single-tap home kegerators, a 10 lb aluminum CO2 tank is the right answer. 5 lb works for occasional pourers and tight spaces but you’ll resent the refill trips. 20 lb pays off if you’re running two kegerators or you also force-carbonate homebrew, otherwise it’s overkill. Below: the actual cost math, the refill economics reality that nobody talks about, and the decision flowchart that fits your specific setup.

The three inputs that determine the right size

Forget the generic “5lb for occasional, 10lb for regular, 20lb for heavy” advice. The real decision matrix has three inputs:

Input	Why it matters
Your pour rate	A 5lb tank lasting 6 months at slow pour rates costs the same per refill as one lasting 3 months at higher pour rates. The bigger tank’s savings show up faster at higher pour rates.
Your refill cost delta	At a typical US welding supply: 5lb refill ~$9, 10lb refill ~$15, 20lb refill ~$22. The per-pound cost drops sharply at 10lb and slightly more at 20lb.
Your storage and lifting tolerance	A 5lb aluminum tank weighs ~10 lbs full and fits anywhere. A 20lb tank weighs ~40 lbs full, needs floor space next to the kegerator, and you’ll feel every refill trip.

Anyone telling you the answer without asking about your pour rate is selling you what they have in stock.

The actual cost math

A half-barrel keg (15.5 gallons) typically needs about 0.6-0.8 lbs of CO2 to dispense fully, depending on pressure setting, line length, and how aggressive your pour-and-let-it-settle style is. Call it 0.7 lbs average.

Tank	Cost (new aluminum)	Refill cost	Kegs per fill	Cost per keg dispensed (gas only)
5 lb	$60-80	$9	~7	$1.28
10 lb	$90-120	$15	~14	$1.07
20 lb	$140-180	$22	~28	$0.78

Gas cost per keg drops from $1.28 to $0.78 as you upsize. That’s a 39% saving, but in absolute terms the difference is $0.50/keg. Over 30 kegs (about 3-5 years for an average home owner), that’s $15. Not life-changing.

The real savings aren’t in dollars. They’re in refill trips.

A 5lb owner pouring 2 kegs/month refills every 14 weeks (about 4x/year). A 20lb owner with the same pour rate refills every 14 months. If your tank is emptying faster than these estimates, you likely have a slow leak (diagnosis here) since gas usage is dominated by leaks more than dispensing in most home setups. That’s the difference between “annual chore” and “decade chore.” When customers tell me about CO2 tank regrets, they almost never complain about the dollar cost. They complain about driving to the welding supply.

Tank by tank: who each size is for

5 lb tank: who it’s for

• Occasional pourer: 1 keg every 2-3 months
• Tight spaces: small under-counter kegerator with no external room for a tank
• First-time owners who want to test the hobby before investing
• Renters or anyone who moves frequently

What you give up: refill frequency. At average home pour rates, you’ll refill 3-5 times a year. If your welding supply is 20 minutes away, that’s an annual time tax. You also can’t force-carbonate a homebrew keg easily because the small tank empties before the beer fully equilibrates.

Verdict: 5 lb is a starter tank. Most owners upgrade within 18 months. If you know you’re not pouring frequently, fine. Otherwise, skip to 10 lb.

10 lb tank: the default recommendation

• Single-tap home kegerator
• Average to above-average pour rate
• Some homebrew force-carbonation
• Reasonable floor space next to the kegerator

This is what I recommend to 80% of new kegerator owners. It hits the per-keg gas cost sweet spot without becoming a storage burden. Refills happen 1-2 times per year for typical home use. The aluminum version weighs ~17 lbs full, manageable for one-person carry to the car.

What you give up: nothing meaningful. The price step up from 5lb is $30-40 one-time; the operational simplicity is worth that within the first year.

Verdict: default choice. If you’re not sure, get 10 lb.

20 lb tank: when it pays off

• Two-tap or three-tap kegerator
• Frequent force-carbonation of homebrew kegs
• You absolutely hate refill trips
• You have a basement or garage with dedicated space

A 20 lb tank weighs ~30 lbs empty and ~50 lbs full. It needs floor space (typically 8” × 24”). It refills 2-3x less often than a 10 lb, but each refill is a heavier lift. The per-keg gas cost is the lowest of the three sizes, but the absolute savings don’t justify it unless you’re pouring 30+ kegs per year.

A US-based customer with a single-tap kegerator started on a 5lb tank, ran through four refills in six months (at $9 each). After the fourth he ordered a 10lb tank for $65 and reckoned his break-even at about 8 months. Three months in, he’s down to one refill projected in 18 months instead of every six weeks. The annoyance saving outweighed the dollar math by a wide margin. He skipped 20lb because the basement space wasn’t worth it for a single tap.

Verdict: 20 lb is for multi-tap setups or homebrew force-carbonators. Single-tap home use rarely justifies it.

The refill economics reality

Most guides leave this out. Where you can refill matters as much as which tank you buy.

Welding supply stores carry CO2 in all sizes and refill on the spot. Price: $9-25 depending on size. Hours: business hours weekdays, often half-day Saturday. This is the gold standard for most US home owners.

Homebrew shops often carry 5 lb and 10 lb in exchange. They may not handle 20 lb, or may have to send your tank out. Price: usually $1-3 higher than welding supply. Hours: weekend availability is the trade-off.

Big box hardware stores (Home Depot, Lowes) sometimes carry 5 lb exchanges via Airgas partnership. Pricier per fill, but you can hit them at 9pm on a Sunday. Worth knowing about for emergencies.

Tank exchange programs vs refills. Some suppliers swap your empty tank for a full one rather than refilling yours specifically. Pros: faster (no wait), accepts tanks with expired hydro dates because they recondition them anyway. Cons: you lose any nice tank you’ve bought, you get whatever they hand you, sometimes scuffed or older. For 5 lb owners who refill often, exchange is great. For 20 lb owners with a specific tank, refilling is better.

Before you buy a tank size, check what your nearest supplier carries in stock for that size. A 20 lb tank you can’t refill locally is worse than a 10 lb that’s always in stock.

Aluminum vs steel

For home kegerator use, aluminum is the right call almost every time.

Feature	Aluminum	Steel
Weight (5 lb empty)	~7 lbs	~12 lbs
Weight (10 lb empty)	~11 lbs	~20 lbs
Weight (20 lb empty)	~22 lbs	~30 lbs
Cost premium	+15-20%	baseline
Rust resistance	Excellent	Requires care
Drop resistance	Dents	Dents less, more rugged
Hydro test interval	5 years	10 years
Best use	Stationary home	Workshop, transport

The cost premium is small. The weight saving is significant: a 20 lb steel tank with hydro testing every decade costs you ~50 lbs of total weight to move around vs ~22 lbs for aluminum. If you’ll never move the tank, steel is fine; aluminum is still nicer.

Common mistakes when buying

Buying steel because it’s slightly cheaper. Almost always regretted within a year of carrying it to the welding supply.

Buying without checking your nearest refill supplier. If they only stock 5 lb, your 20 lb tank becomes a paperweight.

Buying used without checking the hydro date. A tank within a year of expiry is essentially a one-fill purchase. Most welders won’t fill expired tanks.

Buying multiple small tanks instead of one bigger one. “I’ll just have two 5 lbs as backup” creates two sets of refill chores and zero cost saving.

Cheaping out on the regulator instead of the tank. A $19 single-gauge regulator will outlast any tank you buy. The tank choice doesn’t depend on the regulator choice.

The decision flow

Do you pour more than 2 kegs/month?
├── Yes → Are you running multiple kegerators or force-carbonating?
│         ├── Yes → 20 lb aluminum
│         └── No  → 10 lb aluminum
└── No  → Do you have space next to the kegerator for a 10 lb tank?
          ├── Yes → 10 lb aluminum (you'll grow into it)
          └── No  → 5 lb aluminum (starter, plan to upgrade)

That’s the whole flowchart. Pour rate sets the floor; storage space breaks the tie.

What I’d actually buy today

For a typical first-time home kegerator owner in the US, asking the same question:

• 10 lb aluminum CO2 tank: ~$95
• CGA-320 dual-gauge regulator: $35 (avoid single-gauge for $20; the second gauge tells you when the tank is emptying before the beer goes flat)
• 5/16” gas line with MFL fittings: $10-15
• Sankey D coupler (or whatever matches your keg style): $25-40

Total: ~$165-185 for the gas side of a home kegerator. Lasts 5-7 years before any component needs attention. Pair with periodic beer-line cleaning and the system runs reliably for the long haul. The 10 lb tank is the centrepiece of that decision and the one you’ll appreciate most every time you don’t have to drive to the welding supply.

Hidden costs and gotchas (what the spec sheet doesn’t mention)

Tank shopping focuses on the obvious numbers: capacity, price, weight. The cost breakdown that actually catches people out is downstream of the spec sheet.

Hydrostatic testing. Every aluminium tank in the US needs hydrostatic testing every 5 years; steel tanks every 10. A hydro test costs $15-25 and is required by law for the tank to be legally refilled. Many refill stations refuse expired tanks outright. The math: if you buy a 4-year-old used tank for $50 saving, you’ll spend $15-25 on a hydro test within a year, AND you’ve lost a year of the new hydro window. Buying new at $90 is often better value over a 5-year ownership window.

CGA-320 fitting standard. US CO2 tanks use the CGA-320 fitting. Most homebrew regulators are CGA-320 compatible, but not all. Imported beverage gas regulators sometimes use European DIN 477-9 fittings, which look similar and won’t seat properly. Confirm the fitting standard before buying. Wrong fitting = $25 adapter or a botched gas leak.

Exchange vs ownership. Tank exchange programs (Airgas, Praxair, some homebrew shops) take your empty tank, hand you a full one, and don’t care which specific tank you walked in with. This is faster (no waiting for a fill) and easier (they handle hydro testing). The trade-off: you don’t get your specific tank back, you get whatever they hand you. For owners who care about tank cosmetics, ownership, or who’ve bought a premium aluminum tank, refilling is better. For most home users doing 4-5 refills a year, exchange is the right call.

Multi-tap scaling. A two-tap kegerator on one CO2 tank doesn’t use twice as much gas (the unused tap doesn’t consume gas), but it does scale with consumption. If both taps are active, a 10lb tank lasts ~8-10 kegs (~6-9 months at moderate pour rates) instead of the ~14 kegs single-tap. A three-tap or four-tap setup typically wants a 20lb tank as the minimum economic choice.

Transport and storage. A 20lb tank weighs ~40 lbs full. Cars and homes can’t always accommodate them easily. Vertical storage is preferred (the valve is designed for it); horizontal storage works but slightly elevates the risk of releasing liquid CO2 through the regulator during pours. Don’t store tanks in unventilated spaces, CO2 displaces oxygen and high concentrations can asphyxiate in extreme cases (rare but real).

Insurance + landlord considerations. Some renters’ insurance excludes “compressed gas containers above X capacity” without explicit declaration. Most don’t, but check. Landlords occasionally object to 20lb tanks in apartments; 5lb and 10lb tanks rarely raise eyebrows.

The kit choice isn’t just “which tank fits my pour rate”, it’s the full operational picture. The 10lb sweet spot exists because it threads through all of these constraints cleanly.

If you’re still working out whether the whole setup is worth it before you spend on the gas side, the kegerator ROI calculator does the cost-per-pint math against your local pub.

After the CO2 decision: the hosting math

CO2 sizing is gear math. The next problem most hosts hit at home parties: who paid for what when 12 friends drink through your keg.

Related reading

For style-specific CO2 pressure settings: kegerator CO2 pressure for IPA and for lager. For foam troubleshooting when CO2 is the suspect: kegerator beer foamy after a CO2 swap. For flat beer: why is my kegerator beer flat. For broader CO2 context: CO2 systems pillar. For tank refills: where to refill CO2 tank. For party hosting math: hosting a kegerator party for 15 mates and party drink calculator.

---

Part of the CO2 systems cornerstone series. Up next: CO2 pressure settings for different beer styles, and finding tank leaks before they empty.

People also ask

Is a 5lb CO2 tank too small for a single kegerator?

It's not undersized in terms of function. A 5lb tank dispenses 4-7 half-barrel kegs before refilling. The constraint is the refill frequency and the time cost of trips to the welding supply, which is what most owners actually regret about a 5lb tank within the first year.

How much does a CO2 refill typically cost in 2026?

At US welding supply stores: roughly $9 for a 5lb refill, $15 for 10lb, $22 for 20lb. Per pound, the larger tanks are dramatically cheaper to fill. Big box stores running Airgas exchange programs charge premium ($15-25 for 5lb exchanges).

Should I buy aluminium or steel CO2 tanks?

Aluminium for home use, almost without exception. Lighter, doesn't rust, costs only 15-20% more new. Steel makes sense if you're transporting tanks frequently or treating them roughly in a workshop, but for stationary kegerator use, aluminium is the better call.

Can one CO2 tank serve two kegerators?

Yes, with a dual-output regulator (or a single regulator + a splitter). Most home setups doing this use a 10lb or 20lb tank because the dual draw empties tanks faster. Two-tap households running a 10lb tank typically refill every 6-9 months.

How do I know when my CO2 tank is nearly empty?

The high-pressure gauge isn't reliable — CO2 stays at ~750-850 PSI until the liquid is gone, then drops fast. Weigh the tank instead. A 5lb tank weighs ~12-14 lbs full (aluminium) and ~7-9 lbs empty. The cylinder itself is heavy; the gas is light.

How long can I leave a CO2 tank connected before it expires?

CO2 itself doesn't expire. The tank does require periodic hydrostatic testing: every 5 years for aluminium, every 10 years for steel in the US. Most refill stations won't fill an expired tank. Check the date stamp on the tank's collar.

Sources & references

Claims in this article cross-check against the following. We link out so you can verify.

1. CO2 Tank Sizing Recommendations — KegWorks reference
2. DOT Cylinder Specs (CGA-320) — US Department of Transportation standard
3. Aluminium vs Steel Cylinder Standards — Airgas manufacturer
4. CO2 refill cost survey — HomeBrewTalk community
5. Taprite Regulator Compatibility — Taprite manufacturer