Solar hot tub kit: run your tub on sunshine

What a solar hot tub kit really is

"Solar hot tub" can mean a few different things, so let's be clear. We're not talking about a black hosepipe on the shed roof warming a trickle of water. A modern solar hot tub kit is three parts working together: solar PV panels that generate electricity from daylight, a battery that stores it, and an efficient air-source heat pump that turns that electricity into water heat several times over. Together they let you run a tub largely on free or stored energy instead of expensive grid power.

It bolts onto the inflatable or foam tub you already own. Below we explain how the three parts combine, and — importantly — we're honest about what solar can and can't do across the UK seasons. For a number tailored to your setup, use the savings calculator; for the cost picture generally, see our running costs guide.

How the three parts work together

• Solar PV panels turn daylight into electricity whenever it's light — most on bright days, less when it's dull, nothing at night.
• The battery is the clever bit. It stores surplus solar during the day so you can heat in the evening, and it can also charge overnight on a cheap off-peak tariff (around 12.5p/kWh on Economy 7 — roughly half the ~26p/kWh Ofgem cap for summer 2026, which changes quarterly). So you're always spending the cheapest energy available: free sun first, cheap overnight power second.
• The heat pump multiplies whatever electricity it's given. At a COP of around 3–5 in milder weather, a modest amount of solar or stored power turns into a lot of water heat — far more than a built-in resistive heater (COP 1) could manage from the same energy.

That multiplication is why solar plus a heat pump is such a good pairing: the heat pump makes every hard-won solar unit stretch three to five times further. Our heat pump vs electric heater guide explains the COP difference in full.

The honest bit: solar and the seasons

We'd rather you go in with clear eyes than be disappointed. UK solar has an awkward mismatch: generation is strongest in summer, when your tub needs the least heating — and it collapses in winter, exactly when demand peaks.

• Summer: long, bright days and warm air (so the heat pump runs at its best COP) mean a well-set-up kit can run the tub close to free. This is solar at its most rewarding.
• Spring and autumn: solar makes a solid partial contribution; the battery and a little off-peak power top up the rest.
• Winter: generation is low and heat pump efficiency dips (COP nearer 2–3 in the cold), so realistically solar covers only part of the load. The battery charging on cheap overnight power does the heavy lifting, with the heat pump keeping even that grid energy efficient.

So the honest headline is: near-free in summer, partial in winter, and never worse than running the built-in heater on peak-rate grid power. Anyone promising year-round free hot tub heating from British sunshine isn't being straight with you.

The Full Eco Conversion Kit

Our Full Eco Conversion Kit brings all three parts together as one retrofit package for a tub you already own — £2,195 (founder price £1,845), currently on reserve/enquiry. It pairs the solar panel and battery with the efficient air-source heat pump, all app-controlled, and it's UK-built. If you'd rather start smaller, the Heat Pump Only option is £895 and delivers most of the running-cost saving on its own; you can add solar and storage later.

The kit fits the popular inflatable and foam tubs — see, for example, our Lay-Z-Spa heat pump and solar kit page. It's the same approach whether your tub is a Lay-Z-Spa, CleverSpa, Intex, Wave Spa or Canadian Spa.

We run this kind of kit ourselves in the UK and monitor its measured performance, which is how we can talk about COP and seasonality without hand-waving — and why, instead of quoting you a headline saving, we send you to the savings calculator to model your own tub and tariff.

The clever bit: a kit that runs itself

You've seen the hardware — panel, power box, heat pump, switch box. What turns four good components into one genuinely smart system is the software joining them up. It's an app that, honestly, knows your tub better than you do.

Give it a target temperature and walk away. From then on it's learning: your garden's peak generation window, the routine of when you actually use the tub, and how quickly your water loses heat overnight. It pairs that with the local weather forecast to plan ahead — pre-warming while free solar is flowing, and deliberately holding off on paid energy when tomorrow looks sunny.

• Set and forget: pick a temperature, or commit a day ahead for guests
• Learns daily: weather-aware, routine-aware, loss-aware
• Live status anywhere: generation, battery, heat draw and water temp, second by second
• Daily scoring: energy harvested, heat delivered, and pounds saved versus mains

Nothing about how you use your tub changes — just the bill and the carbon. Questions about your setup? Get in touch.

Is a solar hot tub kit right for you?

It suits you if you use your tub through much of the year, you've got somewhere to mount a panel with decent daylight, and you like the idea of running on your own generation and cheap stored power rather than peak-rate grid electricity. If you mainly soak in summer, it's especially well matched — that's when solar gives the most.

Not sure where to start? Get in touch and we'll help you work out whether the Heat Pump Only option or the full kit fits your tub and your winters. Hot water needn't cost the earth.

Frequently asked questions

Can a solar hot tub kit run my tub for free?

In summer, a well-set-up kit can come close, because generation is high and the heat pump runs at its best efficiency. Across the whole year, no — winter generation is low and demand is high, so the battery and cheap off-peak power fill the gap. We'd call it near-free in summer and a partial contribution in winter, which is the honest answer.

Do I need to replace my hot tub to use a solar kit?

No. The kit is a retrofit — it adds solar, battery and an efficient heat pump to the inflatable or foam tub you already own, such as a Lay-Z-Spa, CleverSpa, Intex, Wave Spa or Canadian Spa. You keep your tub; the kit changes how it's heated and powered.

What does the Full Eco Conversion Kit cost?

It's £2,195, with a founder price of £1,845, currently on a reserve/enquiry basis. If you'd rather begin with just the efficiency gain, the Heat Pump Only option is £895 and you can add solar and storage later. For what it might save on your specific setup, use the savings calculator — it depends on your tub, tariff and usage, so we don't quote a one-size figure.