Search for solar equipment and you'll quickly meet two similar-sounding parts: the charge controller and the inverter. They do different jobs, and which one you need depends on the type of system you're building. This guide explains the difference, including the MPPT vs PWM question, and shows which one a plug-in solar kit uses.
What a solar charge controller does
A charge controller sits between your panels and a battery. Panel output changes with sunlight, and a battery needs a controlled charge. The controller regulates that power so the battery charges safely and isn't overcharged.
There are two common types:
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PWM (pulse width modulation): simpler and cheaper. It works well in small, basic systems where panel and battery voltages are closely matched.
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MPPT (maximum power point tracking): more advanced. It continuously adjusts to pull the most power from the panels, and it usually performs better in cold or cloudy conditions and in larger systems.
Charge controllers belong to battery-based setups, such as off-grid cabins, caravans and boats.
What an inverter for solar panels does
Solar panels produce direct current (DC). Your home runs on alternating current (AC). A solar panel inverter converts one to the other so your appliances can use the power.
Without an inverter, the electricity from your panels can't run a kettle, a fridge or a TV. In a grid-connected system, the inverter also makes sure the power it produces matches the grid's requirements.
Microinverters vs string inverters
There are two main types of solar inverter in the UK:
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String inverter: one larger unit that handles a whole row ("string") of panels. It's common on rooftop installations.
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Microinverter: a small unit that converts power at the panel level. It's well suited to small systems because it needs no separate large inverter box.
Plug-in solar kits use microinverters. Each panel has its own conversion, so shade on one panel doesn't pull down the others as much as it can with a single string.
Why a plug-in kit doesn't need a charge controller
A charge controller only matters when you're charging a battery. A plug-in kit has no battery in the basic setup. The panels feed the microinverter, the microinverter converts the power, and your home uses it straight away.
A microinverter also does the job of tracking the best operating point of the panel, similar to what MPPT does for a battery system. So you don't need a separate controller on a standard plug-in kit.
What to look for in a solar inverter
If you're choosing an inverter for solar panels, check:
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Power rating: it should suit the output of your panels.
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Type: microinverter for small plug-in systems, string inverter for larger rooftop systems.
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Grid compliance: in the UK, look for equipment that meets grid connection requirements. ENA registration is a good sign.
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Compatibility: make sure it works with your panels and your setup.
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Support and warranty: check what the supplier offers.
The Hoymiles HF-800-WB
If you want a solar inverter UK buyers can order directly, take a look at the Hoymiles HF-800-WB plug-in solar microinverter. It's designed for plug-in setups and works with the kind of panels used in kits like the Solarfy Solo 455 W and Duo 910 W. Check the product page for the full specifications before you buy.
Wondering what an inverter costs? See our guide to what affects solar panel inverter prices in the UK.
Frequently asked questions
Is MPPT always better than PWM?
MPPT is usually more efficient, especially in larger systems and in cold or cloudy weather. PWM can be fine for small, simple battery systems where cost matters most.
Do plug-in solar kits need a charge controller?
No. A standard plug-in kit has no battery, so the microinverter handles the conversion instead.
Can I use a microinverter with a battery?
It depends on the battery and the system. Always check compatibility before buying.
The bottom line
A charge controller is for charging batteries, and an inverter turns panel power into the electricity your home uses. For a plug-in kit, the microinverter is the part that matters. Browse our plug-in solar products to see what's available.