Guide To Solar Panel Inverters

In Summary: Inverters For Solar Panels

Our guide to inverters for solar panels is a 10-minute read. If you’re short on time, bookmark this for later and read this short summary instead…

Solar panels absorb sunlight and produce direct current (DC) electricity. However, UK households use AC electricity. The role of an inverter is to convert this power from DC to AC. 

There are three main types of inverter:

• String: The best type of inverter for a cheap solar panel setup
• Micro: A better solution for systems where one panel produces more electricity than another (e.g. some panels are shaded by trees)
• Hybrid: The best type of inverter for those using battery storage and that plan to sell excess electricity back to the grid

Depending on the type of unit you choose, expect your inverter to cost in the region of £750-£2,250. 

In terms of sizing, you’ll need a unit that matches your solar panel output; a 4kW system will need an inverter that’s approximately 4kW.

Solar inverters last 10-15 years (less than the life of your solar panels), so make sure you buy one with a long warranty. When your inverter’s efficiency drops considerably from its 93-96% peak, this is a sign that it needs replacing.

Use our clickable solar panel tool here, which will suggest the best solar panel system for your property, including the most suitable inverter.

Guide To Solar Panel Inverters

What is a Solar Panel Inverter?

A solar panel inverter is a crucial part of your system. The question is, what is it? 

When solar panels absorb sunlight they generate electricity in the form of direct current (DC). However, appliances in UK households use alternating current (AC). 

The role of the inverter in a PV solar panel system is to convert DC to AC, so electricity is usable in your household. Without an inverter converting this electricity, the energy produced by your panels would be unusable. 

Types of PV Solar Inverters

There are a few types of solar PV inverters. The most common types are: 

• String inverters
• Micro inverters
• Hybrid inverters

Our clickable solar panel tool here will automatically suggest the most suitable inverter for your solar panel setup.

String Inverters: Best Inverter For Low Budget Installations

String inverters for solar panels are common in low budget installations. They connect a series of solar panels via a "string", enabling DC electricity to be converted to AC so it's usable in your home.

If you're looking to keep installation costs down, a string inverter for your solar panels is a great option. These are one of the cheapest PV inverters to both buy, and to install.

However, it's worth noting that any panels attached to a "string" will be affected by a lack of efficiency from a single panel. For example, if you have 1-2 panels that are shaded by trees whereas others are not, the whole string's (and group of panel’s) efficiency will drop. 

So, if you expect each panel to be producing different levels of electricity (due to shading or orientation), a string inverter is not going to be suitable.

Micro Inverters: Best Inverter For High Efficiency

Whilst micro inverters can be attached to multiple panels, attaching them to a single panel offers the highest level of efficiency.

As we noted above, string solar panel inverters are attached to a group of panels; all panels are affected by low efficiency panels in a “string”. This is a big problem if one panel produces less electricity than another. A micro inverter solves this problem.

If you expect certain panels to perform much better than others, segregating them by using a micro inverter is definitely the way to go.

Likely to have individual panels producing more / less electricity than others? The best unit for your system will be a string inverter.

Hybrid Inverters: Best Solar Inverter For Systems Using A Battery

If you’re looking for the best inverter to use with a solar battery, that’s going to be a hybrid unit.

You can view a hybrid inverter as “smart” when comparing it to a typical string or micro inverter. It’s much more flexible in terms of what it can do, with many modern hybrid units coming with apps to control them remotely.

This means you’ll be able to use power from your panels, solar battery storage, or redirect electricity so it can be sold back to the grid. 

Overall, this offers both flexibility and higher efficiency in comparison to using a string inverter. 

Configure your perfect solar panel system including the most suitable inverter, by using our solar panel tool here. 

How Does a Solar Panel Inverter Work?

Inverters for PV solar panels work by converting DC electricity generated by the panels to AC electricity. 

If you're planning a DIY solar panel installation, you need an inverter, otherwise any electricity you generate will be unusable; UK households use AC electricity, not DC!

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How they work is reasonably simple:

1. Solar panels are exposed to sunlight
2. Electricity flows from the panels to the inverter (DC)
3. The inverter then directs electricity (DC) towards the transformer
4. The transformer reduces the voltage and in the process, converts the electricity generated to AC
5. Your system incorporates transistors, which feed both sides of the transformer as they are flicked on and off during the conversion process
6. Electricity is now AC and usable with any excess fed back to the grid (which you'll get paid for), or if you have one, stored in your solar battery

How Much Does A Solar PV Inverter Cost?

The cost of a solar panel inverter is going to be directly affected by variables such as:

• It's efficiency during the conversion process
• It’s output
• The type of inverter your choose to integrate with your solar panel system (string, micro or hybrid)
• Brand, build-quality and warranty offered with your unit

If we look at typical costs, expect to pay anywhere between £750-£2,250 for an inverter suitable for solar panels. 

Something noteworthy here is that the government is running a VAT relief scheme until early 2027. This means you'll pay 0% VAT on green energy products, including inverters. 

The 0% VAT scheme only applies if you use a Microgeneration Certification Scheme (MCS) certified installer. MCS is the body that sets minimum standards for low-carbon installations such as: biomass boilers, air source heat pumps, boilers and solar panels.

If you plan to use a MCS installer, you won't need to do anything to qualify for 0% VAT; your installer will do it on your behalf. 

Taking the example of a £2,250 solar inverter? 

You'll pay the RRP minus VAT. That's a total cost saving of £375; you'll pay just £1,875.

Get prices on solar panels including a suitable inverter by clicking here. 

Solar Panel Inverter Installers

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Whilst using a MCS installer isn’t a legal requirement, it’s certainly advisable. 

Small projects (i.e. installing a couple of panels to power outdoor lighting) can be completed with anyone that’s reasonably competent when it comes to DIY. 

However, both spec’ing and installing a full scale solar panel system is a hugely complex project. Not to mention the fact that the 0% VAT benefit on material costs means that the cost of labour is almost covered; non-MCS installers don’t qualify for the 0% VAT benefit.

Looking for a professional installer? 

Jump over to our solar panel pricing page here, or, read our guide to solar panel installers here. 

What Size Solar Panel Inverter Do I Need?

Before purchasing an inverter for solar panels, you don’t just need to pick one from a top brand with a long warranty, you need to pick the correct size too.

So, what size inverter do you need? 

An inverter’s size needs to match the output of your solar panels. If you have a 4kW solar panel system installed, you’ll need an inverter that has a capacity of at least 4kW. 

When looking at specific inverters, this might be listed in watts rather than kilowatts. For example, a 4kW inverter might be listed as a 4,000w unit.

Like-for-like, the smaller the inverter, the lower the price. But, trying to save a few hundred pounds on a cheaper inverter makes little sense. 

A solar panel system costs £7,000-£12,000 on average, and an undersized inverter could reduce efficiency dramatically; buying an undersized unit will cost you thousands in lost electricity production in the long-term.

To see exactly what size solar panel system you need, use our clickable solar panel tool here. 

Efficiency 

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Solar panel inverters are highly efficient. Whilst panels will generally work at 20% efficiency, an inverter will work at 93-96% efficiency. Of course, this depends on the make, model and quality of the unit you choose, as well as your solar panel setup. 

Why don't inverters work at 100% efficiency? Simply because they require some power (DC) in order to operate. Typically, this is in the 25w-40w range. 

Use our clickable solar panel tool here. It not only picks the most suitably sized solar panel setup for your property, but the most efficient inverter too!

How Long Does An Inverter Last?

Inverters used in conjunction with solar panels typically last 10-15 years, and cost £750-£2,250 to replace. 

Your inverter will offer warning signs when it needs replacing. The most obvious sign is a huge drop in efficiency.

Typically, a solar panel system should be serviced once annually by a MCS certified engineer. As part of a service package, your engineer will check your inverter and let you know if it needs replacing. 

Whilst the typical lifespan is 10-15 years, not all inverters last this long. That’s why it’s important to stick to leading brands that are offering a long warranty; save yourself the worry of an expensive bill for a replacement!

Can Solar Panels Work Without An Inverter?

No, solar panels can’t supply household electricity without an inverter. 

UK households use AC power, whereas the power produced by solar panels is DC. Without an inverter, you won’t be able to convert energy generated by solar panels into usable AC electricity.

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