How to Choose the Right Size Wood Fired Hot Tub

The size difference between AlumiTubs models is smaller than most people expect, and the practical differences in running costs, water use, and wood consumption are modest once the tub is at temperature. The main decision is how many people you want to soak with comfortably, and whether you want the option to host more. When in doubt, future-proof the decision.

This guide addresses the most common assumptions about hot tub sizing, sets the record straight, and gives you a clear framework for making the right call. 

The three AlumiTub sizes at a glance

AlumiTubs are available in three sizes. All three share the same core construction: marine-grade aluminium interior, Canadian Western Red Cedar exterior, triple-layer 360-degree insulation, and the same internally submerged firebox design. The only thing that changes between them is diameter and the volume of water they hold.

 

Model	Diameter	Standard depth	Depth options	Suits
Small	5 ft	38 inches	44 in (all heating types); 48 in (electric)	1 to 2 people
Standard	6 ft	38 inches	44 in (all heating types); 48 in (electric)	2 to 6 people
Large	7 ft	38 inches	44 in (all heating types); 48 in (electric)	Larger groups

 

One foot of diameter separates each model. That is a smaller physical difference than most people picture when imagining the gap between a two-person and a group-sized tub. The decision, once you understand the actual numbers, often becomes clearer.

 

Five misconceptions about hot tub size

Most of the confusion around hot tub sizing comes from assumptions that sound logical but do not hold up when applied to how wood fired hot tubs are actually built. These are the five most common ones.

 

1. Smaller tubs heat faster

Not necessarily. The volume of water is only one factor in heat-up time. Insulation quality, firebox design, and how the tub retains heat all play a significant role. Because every AlumiTub shares the same 360 degree, triple-layer insulation and the same oversized submerged firebox, the difference in heat-up time between sizes is less dramatic than you might expect.

The Small 2 person wood fired hot tub typically reaches soaking temperature in around ninety minutes from a cold fill. The Standard and Large take two to three hours. That is a meaningful difference for the first heat, but once the tub is at temperature, all three sizes hold heat similarly well. The insulation is doing the same job across the range.

Heat-up time can also be reduced regardless of size: use dry, seasoned hardwood, keep the lid on throughout heating, fill with warm water where available, or add the electric heating and filtration kit to bring the tub up to temperature quickly before switching to wood.

 

2. Smaller tubs use less water

This is not always the case. Water volume depends on the interior space available for water, which is reduced in all sizes by the firebox, any seating configuration, and the depth of the tub. The relationship between diameter and actual water capacity is not linear. 

More relevant is how you manage the water. Regardless of size, water use is largely a function of how often you drain and refill, how well you maintain the water between uses, and whether you add filtration. A larger tub with filtration can use less water over a season than a smaller tub drained after every use. Learn more about how to conserve your hot tub water.

 

3. Smaller tubs use less wood

Once a cedar hot tub is at soaking temperature, ongoing wood consumption across all three sizes is similar. Heat retention is primarily driven by the insulation and lid, not by the volume of water. All AlumiTubs maintain temperature with roughly an armful of wood per day once the initial heat has been established.

The quality of the wood matters far more than the size of the tub. Dry, seasoned hardwood burns efficiently and transfers heat directly. Wet or green wood uses energy on evaporation rather than heating, which increases consumption regardless of which model you own.

 

4. Smaller tubs take up significantly less space

The diameter difference between the Small and the Large is two feet in total: five feet versus seven feet. In practice, the footprint difference is modest. What shapes the space requirement more meaningfully is clearance for comfortable access on all sides, chimney clearance of at least ten feet from any flammable structure, and whether you are adding the heating and filtration kit, which adds approximately one and a half feet to the side of the tub where it attaches.

If space is genuinely constrained, the Small is the right answer. But if the question is simply whether a Standard or Large will fit, the difference is one foot of diameter. Many owners who measure it out are surprised by how little space separates the two.

 

5. Smaller tubs cost significantly less

The price difference between sizes is more modest than most people anticipate. All three models represent a meaningful investment in a product built to last a lifetime, and the quality of construction is identical across the range. What you are paying for is not primarily volume of material: it is the handcrafting, the pressure testing, the marine-grade aluminium, the warranted structural integrity, and the design refinement that has gone into each tub over more than two decades.

It is worth being cautious about very low-cost alternatives in any size. Wood fired tubs built without an aluminium interior will eventually leak, require ongoing maintenance to slow rot, and are likely to need replacement within a decade. The initial saving tends not to hold over time.

 

What actually differs between sizes

With the misconceptions set aside, here is what genuinely changes as you move up in size.

Factor	Meaningfully different?	Notes
Initial heat-up time	Yes	Small: ~90 min. Standard and Large: 2 to 3 hours from cold
Ongoing wood consumption	No	All sizes retain heat similarly once at temperature
Water use per fill	Modest	Difference is smaller than diameter suggests due to firebox and interior space
Physical footprint	Modest	One foot of diameter between each model
Seating capacity	Yes	The most significant practical difference between sizes
Price	Modest	Less difference than most buyers expect

 

The case for future-proofing your decision

AlumiTubs are built to last a lifetime. That is not a phrase used loosely: the first tubs produced more than twenty-five years ago are still in use today, and the structural warranty runs for twenty-five years. When you are buying something you will own for that long, the decision deserves a long-term frame.

The most common thing owners of smaller tubs say in retrospect is that they wish they had gone larger. Not because the Small is inadequate, but because circumstances change. A couple becomes a family. Friends start visiting more. The tub becomes a gathering point and the original two-person calculation starts to feel limiting.

The most common thing owners of larger tubs say is nothing, because having more space available than you occasionally need creates no problems.

If you are genuinely torn between two sizes, the practical advice is to go with the larger one. The difference in day-to-day running costs is modest. The difference in what the tub allows over a lifetime of use is not.

 

How to conserve water regardless of size

Water management is a shared consideration across all three sizes. These practices apply regardless of which model you choose.

 

The practical test

There is a simple way to arrive at a confident size decision before committing to anything. Take a garden hose and lay it out in a circle on a flat surface at the diameter you are considering. Stand inside it with the people you plan to soak with most often. Adjust for how close together you want to be sitting.

That is the most accurate preview of what the tub will feel like in use. No specification sheet or capacity estimate will tell you as much as standing in a circle with the people you plan to share it with.

If you are still uncertain, the AlumiTubs team is available to talk through the decision based on your property, your intended use, and any site-specific considerations. Reach out directly or visit the detailed size guide for more.