I remember the first time someone told me about the Solar iBoost+, I honestly thought it was just another overhyped device claiming to slash energy bills. But after seeing it work firsthand, I completely changed my mind.
Marlec designed this clever piece of kit specifically to help homeowners stop wasting the free energy their solar PV system produces every single day, and instead use that power to do something genuinely useful, like heating water for free.
How Does the Solar iBoost+ Work?
Intercepting the Grid
Most domestic solar PV systems quietly send their surplus energy straight back to the National Grid the moment your home stops needing it, and unless you’re watching closely, this happens completely automatically without you ever knowing.
It steps in before that happens, grabbing that excess energy and putting it to work inside your home instead. It sits between your fuse spur and your immersion heater, using its wireless communication to coordinate everything without a single data cable or mains cable running across your walls.
Dynamic Power Shifting
The Sender does the heavy lifting on the monitoring side. It wraps a clamp around the live wire at your electricity meter and constantly watches your energy use versus your solar generation.
The moment it spots at least 100W of power heading toward the grid, it fires a signal wirelessly to the Controller, which immediately starts diverting that power to heat your water.
If you switch on a kettle or another appliance mid-session, the system automatically adjusts in real time, pulling energy away from the heater and feeding your appliances first, then resuming water heating once the demand drops again.
The water only heats up to the maximum thermostat setting of your immersion heater, so there’s zero risk of overheating.
Savings in Real Time
What makes this genuinely impressive is the real-time feedback it gives you. Right there on the screen, you can see 0.67 kilowatts actively heating your cylinder, with saved today sitting at 0.37 kilowatt hours, saved yesterday at 1.15 kilowatt hours, and the last seven days and last 28 days tallied up neatly below.
Your installer mounts the Sender at the utility meter with the clamp firmly closed so it cannot work loose, pairs it with the Controller in the airing cupboard, and from that moment your microgeneration system stops feeding the grid for nothing and starts filling your hot water cylinder with free hot water instead.
Wireless Logic, Effortless Heat
Setting it up is straightforward. Inside the box, you get the two key parts: the Controller and the Sender with its clamp.
Your installer or electrician clips the Sender onto the live wire at your utility meter, tucks the Controller into your airing cupboard near the hot water tank, and connects everything to your immersion heater.
Since the Sender is battery-operated, there are absolutely no mains cables or data cables to run through the house. The moment the batteries go in, the two units automatically pair, and you’ll see the “Pairing Successful” message on screen.
From that point on, any electricity your system detects being pushed back toward the grid gets diverted straight to your hot water, and you’ll see “Heating by Solar” appear on the display, with a blue light confirming that water heating is in progress.
Key Features of Solar iBoost+
Cord-Free Control
The Solar iBoost+ earns its place on the wall through a combination of features that genuinely make a difference in daily life. Getting it fitted is refreshingly painless.
Your installer wires it directly to your existing immersion heater (as long as it’s 3kW or under), and because the Controller and Sender talk to each other wirelessly with absolutely no cables between them, the whole job stays tidy.
If your system runs 2 immersion heaters, the Solar iBoost+ connects to both and handles the automatic switching between them without you ever needing to intervene. That’s intelligent, intuitive engineering doing exactly what it promises.
Tailored Timing & Dynamic Response
The programmable timer gives you proper control over your heating schedule, letting you set it on a 5/2 basis so weekday and weekend routines work independently.
You can dial in separate winter settings and summer settings to match how your panels perform across the seasons, and the boost switch is always there when you need a quick top-up.
Press it, and the system pulls the full 3kW for 15-minute periods, with the A button and B button giving you additional timer options to suit your routine.
The 100W threshold for surplus detection keeps the system tight and responsive, triggering automatic adjustment only when there’s genuinely useful excess energy available to redirect.
The Savings Dashboard
Where the iBoost+ really shines is in its real-time display. The backlit 32-character LCD with its push buttons makes programming simple, even if you’re not particularly technical, and the energy monitoring it provides is genuinely satisfying to check.
You can scroll through saved today, saved yesterday, saved 7 days, saved 28 days, and total saved all in kilowatt hours, giving you a running picture of your solar diversion performance.
Knowing that every number on that screen represents free energy your system captured instead of giving away makes the whole thing feel incredibly worthwhile.
Specification
Compact Engineering
When you look at the Solar iBoost+ technical specification, it’s clear that Marlec built this for real-world homes rather than ideal conditions.
The device weight comes in at 1.37kg (rising to 1.95kg packaged), and the device dimensions of 288mm x 255mm x 100mm keep it compact enough to sit comfortably in most airing cupboards without taking over the space.
The 2-year product warranty gives you a reasonable safety net, and power usage sits at a very modest 1W to 3W during operation, barely a rounding error on your bill.
Dual Load & Multi-Lingual Smart Scheduling
The immersion heater compatibility covers up to 2 immersion heaters at 3kW each, which handles the vast majority of UK homes without any issues.
Scheduling runs on a 5/2 days pattern with dedicated summertime and wintertime seasonal settings, so the system adapts to your year rather than forcing you to adapt to it.
Language support is genuinely broad for a UK-focused product the multilingual interface covers English, French, German, Italian, Portuguese, and Spanish, making it accessible for a wide range of households.
Flexible Interfacing & Clean Installation
The boost function runs via a push button in 15-minute increments up to a maximum of 2 hours, giving you precise control over any top-up heating you need beyond what the solar surplus provides.
Mounting hardware is straightforward: a centre hook paired with two bottom screws, with cable entry points at both the rear and underside of the unit to keep your cable management neat.
The user controls sit behind a backlit 32-character LCD driven by push buttons, making day-to-day programming and timer scheduling genuinely accessible.
The Solar iBoost+ Buddy
Airing Cupboard Clarity, Delivered Anywhere
The Solar iBoost+ Buddy is one of those optional accessories that sounds like a luxury until you actually use one, then it starts feeling essential.
It functions as a dedicated monitoring display, connecting to your Solar iBoost+ via wireless pairing and giving you a live eco display of exactly what your system is doing at any moment.
When surplus energy is available, and the Solar iBoost+ is active, the Buddy shows you in real time no need to walk to the airing cupboard to check the main unit.
The Glanceable Eco-Gauge
The eco-gauge interface makes energy awareness genuinely accessible. Rather than hunting through menus, a glance at the visual display tells you whether your system is currently capturing surplus energy, how much it has saved, and a running saving history that lets you track performance over time.
You can pull up current savings and historical savings with a single press of the button interface, making savings tracking something you actually do rather than something you intend to do. It turns passive energy monitoring into an active habit.
Seamless Monitoring Upgrades
What I appreciate most about the Buddy is the flexibility around installation timing. You can fit this companion device at the same time as the main iBoost+ unit, or add it later as an add-on once you decide you want richer live monitoring data.
The wireless connection between the two units means no extra cables, no disruption. The supplementary device simply pairs up and starts delivering consumption monitoring and usage awareness straight to wherever you choose to place it in the home.
For anyone serious about understanding their solar diversion performance, it’s a straightforward and worthwhile upgrade.
Solar iBoost+ Cost
Upfront Unit Economics
The iBoost+ price range sits between £250 and £300, depending on which supplier you purchase through, though this upfront cost typically covers the unit itself rather than the full installation cost on top.
Marlec doesn’t publish a full fitted price on their website, but they do list a solid range of spare parts and accessories from £16.95 for an extension cable through to around £80 for the Solar iBoost+ Buddy, so you can factor in any additional cost based on what your setup actually needs. Supplier price and market price can shift, so it’s always worth getting a couple of quotes before committing.
Package Deals & Payback Windows
From a personal perspective, I know of homeowners who paid as little as £200 for the unit, delivered and installed free of charge as part of a wider solar panels package.
Even at the higher end, say £400 for the hardware cost plus fitting, the payback period works out at roughly three and a half years to four years, which is genuinely competitive for a home energy kit.
After that point, every unit of free hot water the system produces represents pure cost savings with no further running cost attached.
The ROI Advantage Over Batteries
The return on investment case for the Solar iBoost+ is hard to argue with once you run the numbers.
The unit cost is fixed, the optional cost of extras like the Buddy is modest, and the product price compares very favourably against alternatives like battery storage systems.
Whether you buy at £250 or stretch to £400, the combination of low power usage, zero ongoing unit cost, and consistent energy saving performance means this device earns back its fitted cost reliably and keeps on saving well beyond that.
FAQs
Is a solar iBoost worth it?
Absolutely, the Solar iBoost+ turns wasted surplus energy into free hot water, and with a payback period of just 3-4 years, the long-term energy savings make it one of the smartest investments for any solar PV homeowner.
What is a solar iBoost?
The Solar iBoost+ is a smart diverter device by Marlec that captures excess solar energy from your solar PV system and redirects it to power your immersion heater, giving you free hot water instead of exporting that power to the National Grid for almost nothing.
How much is a solar iBoost?
The Solar iBoost+ typically costs between £250–£300 depending on your supplier, with optional accessories like the Solar iBoost+ Buddy adding around £80, and full installation costs varying by electrician or installer.
How to use solar iBoost?
Once your installer fits the Sender clamp on your live wire at the utility meter and wires the Controller to your immersion heater, the Solar iBoost+ runs completely automatically. Just set your programmable timer, use the boost button for quick top-ups, and let it handle the rest.
What is the alternative to iBoost?
The main alternatives to the iBoost+ are solar battery storage systems, which store surplus solar energy for broader home energy use. However, they come at a significantly higher upfront cost compared to the simple hot water diversion that the iBoost delivers.