Chapter 3 Topics

3-S: Plug & Play vs 240-volt Systems

(what’s the difference?)

As a major appliance that runs off electricity, you have 3 options for powering up a hot tub. Baby bear (Plug & Play); Mama Bear (120/240 Convertible); Papa Bear (Dedicated 240-volt)

Cheap Plug & Play Hot Tubs

Remember those old-school Easy-Bake Ovens?  The one my little sister had was heated by an incandescent light bulb and she’d make her brothers eat the yucky muffins she’d proudly “baked”.   That’s what I think of when I see some of these cheap “plug & play” units.  No hot tub repairperson would consider them to be “real hot tubs”. 

Some of them work off a heat recovery system using the heat from the pump to warm the water so they take forever to heat up and often cannot maintain max temperature in cold weather. The equipment and electronics are in a sealed unit that can’t be fixed, and many parts are not available so they’re basically disposable.  They are poorly made with cheap materials, don’t perform well and have a short life expectancy.  If a hot tub is an important purchase, it would be false economy to go for one of these.

Dedicated 240-volt hot tubs 

Generally speaking, hot tubs come standard as 240-volt systems and that’s the better way to go if you can swing it.  

A 240-volt system needs to be hardwired (i.e., cannot be plugged in to a household socket), and requires special wiring with a double-wide breaker in your panel.  Building codes typically require a dedicated subpanel installed near the tub as well. For some people, this may not be an option due to cost, electrical limitations or strata regulation. 

120/240v Convertible Hot Tubs

If you want a “real hot tub” but 240-volts is not an option, you might want to consider a “convertible” model.  That means it’s got the same pump/motor/heating element/controls/electronics as a 240-volt hot tub, except you can set it to 120-volt mode.  You can either hardwire it to your panel, or attach a cord with a GFCI-equipped plug on it so you can simply plug it in.

Some dedicated 240-volt systems can be converted to run off 120-volts, although it may require some minor electrical rewiring and a pump swap.  

The limitations of 120-volt mode

If you choose to go with a convertible 120/240-volt system, here are a few drawbacks:

  • You’re limited to simpler options.  Single pump models tend to be more plain, with fewer jets and less features.  
  • You can’t go bigger than a 1.5 hp motor.  If it’s a small tub with few jets, and/or if strong jet pressure is not of utmost importance, then this shouldn’t bother you – you may not even notice any difference.
  • In 120-volt mode, the heater is limited to putting out 1.5KW of power (as opposed to 5KW in 240 mode).  With the hot tub cover on, the water will still heat up to and maintain max temperature no problem, but the temperature will drop faster while in use in cold weather with the cover off, and will take longer to heat up again.  
  • In 120-volt mode, when the pump is on the high-speed setting, the heating element kicks off automatically.  The element will only activate when the pump is on low speed.  

A convertible hot tub set to 120-volt mode should serve you well enough if you’re using the hot tub to relax and hang out for an hour or less in moderate or cool weather.  But if you’ve got the jets going full blast in sub-zero temperatures for extended periods of time with the air controls on max, then the water may begin to cool noticeably by the time you’re done. 

If it’s cost that makes you hesitant to install 240v service, you might consider buying a convertible model and run it in 120-volt mode for starters. If it turns out to be “good enough”, you’ve saved yourself some time and money.  And if you decide to upgrade to 240v service at a later date, that’s still an option.