Off-Grid Hot Tub: Luxury in the Wild or Impossible Dream?

Last updated: September 2026

If you’re here, you’ve probably pictured it: a hot tub at the bottom of a field, in a woodland clearing or next to a cabin, miles from the nearest plug socket, steaming away under the stars. Off-grid hot tubs aren’t my favourite kind of hot tub, but given the number of questions I get about them, I can see why they’re so popular. You get the luxury of a hot tub somewhere private and wild. It’s a lovely idea.

So, can it be done? Yes. But there are some big caveats, and most of them come down to one thing: energy. In this post I’ll go through the three jobs every off-grid tub has to do (heating, filtering and treating the water), the realistic options for each, and what it takes to make one work. Whether it’s worth it is something you’ll be able to decide for yourself by the end.

What is an off-grid hot tub?

As the name suggests, an off-grid hot tub is one built where there’s no mains electricity or gas. It might be at a cabin, a glamping site, a smallholding or simply at the far end of a big garden where running a cable isn’t practical.

Without a mains supply, you can’t use a regular spa pack, more than a few jets, or an air blower. They use a lot of energy, and there’s no small portable power source with enough juice to run them for long. A typical UK spa pack heater alone is 3kW, and a jet pump can draw well over a kilowatt more. So an off-grid tub has to be designed from the ground up around the energy you can actually get.

This post won’t go into the nitty gritty of parts and designs. Instead, I’ll give you an overview of the practicalities you need to think about.

Heating an off-grid hot tub

Since you can’t use a spa pack heater or a mains-powered heat pump, you have four realistic choices.

Wood-burning stove

A wood burner can heat an off-grid tub fairly quickly. You can use the convection (thermosiphon) method, where hot water rises out of the stove into the tub and cooler water sinks back in, or, as I prefer, use a small pump to circulate the water through the stove or a coil. Circulation makes it feel less like a bath and more like a hot tub, and it means you can put a filter in the loop.

The catch is control. There’s no thermostat, so it’s easy to overshoot. The US CPSC recommends keeping hot tub water at 104°F (40°C) or below, so you’ll need a good thermometer and the discipline to stop feeding the fire. I learned this first-hand on a weekend away, which I wrote up in my off-grid wood-fired hot tub review. If you’re in a smoke control area, check the local rules on what you can burn.

Solar heating

The second option is solar thermal: panels that heat water directly, feeding the tub through a heat exchanger or a simple loop. Yes, it takes a few panels and plenty of time, but it’s definitely possible, and once it’s in, the heat is free. It’s also entirely at the mercy of the weather, and it isn’t cheap to buy. The US Department of Energy puts a solar pool heating system at $2,500–4,000 installed, and in the UK the Energy Saving Trust says a solar water heating system costs around £5,300 and provides around 90% of a home’s hot water in summer but only about 25% in winter. For a tub in the UK, think of it as a summer heater or a top-up. I’ve gone through it in detail in Can I heat a hot tub with solar power?

What about solar panels and batteries running an electric heater? For a proper off-grid tub, I wouldn’t. A Tesla Powerwall 3, for example, stores 13.5kWh. That would run a 3kW heater for about 4½ hours and then it’s flat, with nothing left for the lights. It takes about 1.16kWh to raise 1,000 litres of water by 1°C, so heating even a small tub from cold uses far more than that.

Propane (LPG) heater

Gas is much faster. Some people use a portable outdoor propane water heater, and there are propane pool and spa heaters too. But please be careful here:

• Don’t modify gas appliances. I know some people do. It isn’t worth the risk of a fire, a gas leak or carbon monoxide.
• Use an appliance designed for the job, installed outdoors or with the flue and ventilation the manufacturer specifies. In the UK, the law says all gas work must be done by a Gas Safe registered engineer, and that includes LPG. In the USA, use a licensed installer and check whether you need a permit.
• Proper pool and spa heaters usually need some electricity for their controls and ignition. The Raypak Digital range, for example, runs on 120/240V. So you’ll still need a small power supply, and a pump to push water through the heater.

There’s more on gas in my guide to hot tub gas heaters.

Waste heat

If you’re off-grid, you might already be making heat you throw away. My customer Ben runs a diesel generator for his home, and we diverted its coolant through a heat exchanger to heat his tub. Because the generator runs anyway, the heat is effectively free. It’s a clever setup, but it has to be done carefully so the engine’s cooling isn’t compromised. The full story is in How to heat a hot tub for free.

Filtering: what makes it a hot tub

Without filtration, a hot tub is really just a bath. The filtration system is what makes a hot tub a hot tub, because it lets you keep the same water clean for weeks rather than draining it after every soak.

The plumbing for an off-grid tub is fairly simple. The diagram below shows a basic layout.

You’ve got two suction intakes near the bottom of the tub (two, so no single suction point can trap anyone), a pump that you can run from solar, a filter, and two returns higher up to send the clean water back.

How much pumping do you need?

This is the fiddly bit. I recommend aiming for two turnovers a day. A turnover is when all the water in the tub has passed through the filter once. Two a day keeps the water fresh and moving.

1. Work out your tub’s volume. Length × width × water depth, in metres, gives cubic metres. Multiply by 1,000 for litres.
2. Double it. That’s how many litres you need to pump each day.
3. Pick a pump rated for that flow through your filter and pipework, not just its maximum open-flow figure.
4. Choose the lowest current draw you can find. Less current means your battery lasts longer.

Here’s an example with round numbers. A 1,000-litre tub needs 2,000 litres pumped a day. A small 12V circulation pump that really moves 1,000 litres an hour would need to run for two hours. If it draws, say, 40W, that’s about 80Wh a day, which is well within reach of a small solar panel and a leisure battery, as long as you get enough sun and size the battery for a few dull days. Check the real figures for the pump you choose.

So yes, you’ll need some power: most likely a 12–24V system, with a panel, a charge controller and a battery to store your “free electric”. It’s certainly enough to run a turnover cycle and recharge in between, but as you can see, it’s not as straightforward as you might have thought. For more on pump choice and filters, see How to add a circulation pump to a hot tub and cartridge vs sand filters.

Treating the water

Lastly, you need to treat the water so it’s safe to reuse. In my mind, single-use off-grid tubs that you fill, use once and drain aren’t a good idea. They waste a lot of water and a lot of heat. I had some experience of that and reviewed it in my off-grid wood-fired hot tub review.

• Use a proper sanitiser: chlorine or bromine. For chlorine, aim for 3–5ppm, and for bromine 4–6ppm, with pH at 7.2–7.6. My chemical balancing guide explains how, and bromine or chlorine? helps you pick.
• Non-chlorine shock (active oxygen, MPS) is useful for oxidising the gunk bathers leave behind, but it isn’t a sanitiser on its own. It won’t keep killing bacteria between soaks. Use it alongside chlorine or bromine, not instead. See hot tub shock explained and alternatives to chlorine.
• Keep it covered. A lid keeps out leaves and wildlife, stops the sun burning off your chlorine, and holds in the heat you worked so hard for. See how to make a DIY hot tub cover.
• Think about draining. Treated water shouldn’t just go into a stream or pond. Let the sanitiser drop to zero first, and follow local rules.

Off-grid options compared

Heat source	Speed	Running cost	Watch out for
Wood stove or coil	Medium	Low if you have wood, plus your time	No thermostat, hot spots, smoke rules
Propane heater	Fast	Medium to high	Gas safety, flue, needs a little power
Solar thermal	Slow, sunny days only	Very low	Upfront cost, overheating in summer, weak in winter
Waste heat (generator)	Steady	Almost nothing if it runs anyway	Engine cooling, antifreeze, temperature control
Battery + electric heater	Slow	Very high upfront	Batteries run flat in hours

Common mistakes

• Treating it like a normal hot tub. Big jets and a blower won’t run off a small solar setup. Keep it simple.
• No thermometer. With wood or gas, it’s surprisingly easy to go well past 40°C.
• No filtration. You’ll end up draining and refilling constantly.
• Relying on non-chlorine shock alone. It doesn’t leave a sanitiser in the water.
• Bodging the gas. Modified heaters and indoor use of outdoor appliances are genuinely dangerous.
• No cover. Every bit of heat you lose, you have to make again with wood, gas or sunshine.

To build or not to build?

A DIY hot tub project is a fun thing to do. You’ll pull your hair out at some point, I’m sure, but the end result is worth it. Doing it off-grid is a little more challenging, but the people who want this kind of tub are usually up for the challenge. As long as you take care of heating, filtering and water treatment, you’re good to go.

If your site does have a power supply, even a modest one, a conventional tub will be far easier to live with. Have a look at how to build a DIY stock tank hot tub, how to build a DIY wooden hot tub and the best way to heat a DIY hot tub.

Planning your own build?

If your site has a power supply and you’re building a wooden or stock tank tub, my plumbing kits give you the pump, filter and fittings in one box. There’s a heating and filtration kit for cedar and wood tubs (no jets) and the same for stock tanks. For a truly off-grid tub, or any bespoke design built around your site and energy source, I can draw up an architectural CAD and 3D plumbing design.

FAQs

Can you have a hot tub without electricity?

Yes, with a wood-fired or gas heater. But without any power you can’t run a pump or filter, so the water can’t be kept clean for long. A small solar panel, battery and low-voltage pump solves that.

Can I run a hot tub on solar panels and batteries?

A small circulation pump, yes. A normal electric heater, not really: a 13.5kWh home battery would run a 3kW heater for only about 4½ hours.

What is the best heater for an off-grid hot tub?

Wood if you have a supply and don’t mind tending a fire, propane if you want speed, and solar thermal as a free summer top-up. Waste heat from a generator you already run is the best of all, if you have it.

How do you keep off-grid hot tub water clean?

Filter it with a small pump (about two turnovers a day), keep chlorine or bromine in range, shock it regularly and keep it covered.

Is a wood-fired hot tub safe?

It can be, as long as you watch the temperature closely, keep it at or below 40°C (104°F), watch out for hot surfaces near the stove and keep the water sanitised.

Built an off-grid tub, or planning one? Tell me about it in the comments below. I read them all.

Cheers,
Andi

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Thanks - Andi

 

Hi, Andi here. I own Buildahottub.com and also write all of the articles and info pages on the site. Some years back now, I built my own hot tub but struggled to find the information I needed. So, once my tub was complete, I started this website to help others in their own pursuit of hot tub and plunge pools DIY building information.

Fast forward to 2025, I've helped over 1400+ DIY customers just like you all over the world build hot tubs and pools. Have a good look around the site, there are lots of resources here. Please do get in touch if I can help you. - Cheers, Andi