Do You Need a Subpanel for a Hot Tub?

The electrical requirements of a hot tub are often ignored when buying one for the first time, but it can be an expensive thing to overlook. So, do you need a subpanel for a hot tub?

Most hot tub installations do not require a subpanel and instead need a nearby disconnect box that is connected to the main breaker panel. But if that breaker panel is full, adding a subpanel may be necessary.

Inflatable and plug-and-play hot tubs simply require a GFCI household outlet located within 15 feet of the hot tub.

All this talk of GFCIs, disconnects, and subpanels can be very confusing, which is why I’ve used my 15+ years of experience of owning hot tubs to put together this guide.

So we’ll get into the difference between a subpanel and a disconnect box and if there’s any way around adding a subpanel if your main panel is full (hint: I found a workaround once when this happened to me).

So, let’s dive in and get down to business.

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Does a spa need a disconnect?

As a general rule, all 220/240v hot tubs that do not simply plug into a wall outlet will require a disconnect box. The disconnect box is typically located about 5 feet from the hot tub and allows the power to be shut off there rather than at the main breaker panel.

First of all, let’s take a look at what a disconnect is and what it does in greater detail.

A disconnect is a breaker box that cuts off the electrical supply in case of a fault such as a short-circuit or a ground fault. You can also shut off the hot tub manually from the disconnect when you drain it.

Whether you need a dedicated disconnect box depends on the type of hot tub you have.

You won’t need one for a plug ‘n’ play hot tub or an inflatable one running off 110v, but for any 220-240v tub, you will need to install a disconnect or subpanel, and you will have to hard-wire your hot tub to this.

I recommend you use a licensed electrician to wire up to the disconnect, although you can do some of the work yourself, such as laying the cable in a conduit. If you choose to go down this route, make sure to dig 18 inches deep or more and pass the wires through a 1-inch rigid PVC conduit.

But a local electrician will know the exact codes for your city and county.

The size of cables and whether you need 3 or 4 core wiring will be specified in the owner’s manual and will depend on the configuration of the internal electrical equipment.

Some hot tubs have two heaters, some have ozonators fitted, and this has to be taken into consideration when hooking up to the disconnect.

To find out more, this recent article on my website explains exactly what a disconnect does and how to install one step-by-step.

Just click that link to read it on my site.

What type of disconnect do I need for a hot tub?

Most portable, hard-sided 220/240v hot tubs are rated at 50 amps, and the disconnect must be at least equal to the rating of the hot tub and include a GFCI breaker inside of the disconnect box.

If you have a plug ‘n’ play or inflatable hot tub, as I mentioned, you won’t need a disconnect box. But you will still need a ground-fault circuit interrupter (GFCI) outlet.

What is a GFCI outlet, and how do you know if you already have one?

To find out more about this, take a look at this recent article. I get into both regular GFCI outlets (hint: you may already have one), as well as GFCI disconnect breakers. And I also cover whether or not it’s OK to use an extension cord for plug-and-play and inflatable hot tubs.

Just click that link to read it on my site.

Circuit breakers will usually cut out at 80% of the rated amperage, so, as the plugs have 13A fuses fitted, the GFCI outlet should be rated 15A minimum, preferably 20A.

If all you need is a simple GFCI outlet, just make sure it’s within 15 feet of the hot tub.

15 feet is the typical cord length of all plug-and-play and inflatable hot tubs. And extension cords should not be used with them.

And the outlet must be weatherproof if it’s outside, which means it must have a hinged plastic lid.

For more permanent installations, a disconnect box must be fitted, and the hot tub hard-wired to this. Check the warranty to see if the manufacturer insists on certification by a licensed electrician and check the City codes as well. Often these take precedence over the National Electrical Code (NEC).

Will my electrical panel support a hot tub?

All modern homes have breaker panels that can support a hot tub’s 50 amp breaker. However, ensure there are at least 2 open slots to accommodate adding the dual-slot 50 amp breaker. If no slots are available, a subpanel may be necessary.

And adding a subpanel can get expensive (i.e., thousands of dollars).

If you live in an older house, check the rating on the main panel to see what capacity you have, or consult an electrician.

But chances are, somewhere along the way, your home’s wiring and breaker panel have been upgraded.

If you intend to wire into an existing main panel or subpanel, you will have to establish what else is on that circuit.

And you’ll have to do some basic math first, using the formula W (watts) = A (amps) x V (volts). This is not something to be tackled by a novice, so I recommend that you have a dedicated circuit installed by a licensed electrician.

After all, you don’t want your hot tub cutting out every time you use a vacuum cleaner, do you?

Adding a subpanel has the advantage of allowing other appliances to be connected, providing it is sized correctly.

For example, a subpanel in your garage could be used for power tools and gardening equipment, but you will still need a separate shut-off switch for the hot tub.

When I added a hot tub at my last house, my main breaker panel was full (and I hadn’t checked that before buying the hot tub).

Some electricians wanted as much as $3,000 to add a subpanel (and a disconnect box).

Ultimately, I found a reputable electrician who added a combo breaker that accommodated both the hot tub’s 50-amp breaker and one of the other 50-amp breakers. They did that without having to add a subpanel and for just $750. And it worked great.

Wondering how much electricity it takes to run a hot tub per month?

Check out this recent article I posted on my website. I got into the exact costs a hot tub will add to your electricity bill each month, including regular and plug-and-play/inflatable ones. And I covered how much more that cost is in winter.

Just click on the link to read it on my site.

Is a hot tub disconnect box the same as a subpanel?

A subpanel is not the same as a disconnect box. A disconnect box is located about 5 feet from the hot tub and only contains a GFCI breaker for the hot tub, whereas a subpanel may have multiple breakers in it for other items and will not necessarily have GFCI breakers.

To understand the difference, you need to know a little bit about how electricity is distributed around your home.

First, electricity enters your home via a cable that is connected to a main panel.

This is full of switches or breakers that turn off whenever there is a power surge on a particular circuit. It is from this panel that you can disconnect your home from the grid.

From this main panel, you can run circuits to other parts of your home, such as outbuildings and external areas. These circuits can then connect to subpanels, which direct power to other fixed appliances or receptacle outlets, each protected by a circuit breaker.

A disconnect box is another form of a circuit breaker.

But it is usually dedicated to one appliance, such as a hot tub, and it can be wired up to the main panel or a subpanel.

Disconnects are not only used to protect you and the appliance but also to act as the main switch for turning off the power to your hot tub manually when needed.

Portable or built-in hot tubs rated 220-240v must be hard-wired to a disconnect box or subpanel rather than simply plugged into a receptacle outlet.

How far should the subpanel be from the hot tub?

According to the National Electrical Code (NEC), a means of disconnection must be provided within 5 feet of your hot tub. This doesn’t have to be a circuit breaker, it can be a manual switch, but you must have a way of turning off your hot tub for emergency or maintenance purposes.

But city or county codes may have additional specifications.

The NEC also requires GFCI protection to a hot tub, but it doesn’t specify how far away this must be.

It’s normal to install a disconnect box where the switch is situated, i.e., within 5 feet of the tub, but it can be anywhere, even within a shed or garage. Subpanels tend to be inside the house where they can be protected from the weather.

When positioning your cut-off switch, make sure it is within clear sight of the hot tub so that anyone can see it and turn it off in an emergency.

It is a good idea to label this to avoid someone switching it off by mistake, especially if you’ve purposely left your hot tub on to stay warm.

If you decide to appoint an electrician for this work, make sure you get someone experienced in wiring hot tubs because there are some peculiarities an inexperienced electrician might not know about.

Does a Hot Tub Need a GFCI Breaker?

Final Thoughts

Well, now you know you don’t need a subpanel for a hot tub, but if your main panel is full or you have other appliances that could be attached, a subpanel is not a bad idea.

Either way, unless that subpanel is within 5 feet of the hot tub, you will certainly need a GFCI breaker in a disconnect box.

Or, if you have a portable 110v or inflatable hot tub, you’ll just need a plug-in style GFCI outlet.

I hope this gives you the information you need to decide on what you must do to get your hot tub all wired up. If you need any more advice, just reach out to me – I’d be glad to help.

And don’t forget to click on those links to read other associated articles here on my site.

Looking to get a quote on a new hot tub?

Save time and receive multiple quotes for hot tubs from all the best-known brands!

I have arranged with BuyerZone.com to provide free quotes from all the best hot tub manufacturers – with no obligation to buy. Simply complete BuyerZone’s request form below.

Jeff Campbell

Jeff Campbell is a father, martial artist, budget-master, Disney-addict, musician, hot tub lover, and recovering foodie having spent over 2 decades as a leader for Whole Foods Market.

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