The cost of inverters is usually included in the overall solar installation package. However, inverters don’t last as long as solar panels, so at some point you’ll want to know how much you’ll likely have to pay for a replacement inverter.
An inverter is a vital piece of equipment in a solar energy system and without it, your home would get no power from its solar panels.
In this post, we delve into solar inverter costs and types of inverters and their pros and cons.
What Are Electrical Inverters?
- An electrical inverter turns one kind of electricity into another type.
- Inverters used with high voltages and high currents are known as power inverters.
- A solar inverter is a type of power inverter that changes direct current (DC) to alternating current (AC).
- Inverters used in applications with low voltages and low currents are called oscillators.
- Circuits that convert alternating current to direct current are rectifiers.
- Early power inverters – developed in the 1800s – were mechanical and included spinning motors.
- Modern inverters use transistors – solid-state devices with no moving parts.
- They’re made of a semiconductor like silicon – the same material in microelectronics – which controls flow of electricity.
How Do Solar Inverters Work?
Solar panels generate a different sort of electricity than power stations, wind farms and hydropower installations, which produce an alternating current. In an alternating current, the flow of electrons reverses direction at regular intervals and the voltage alternates between positive and negative.
Solar panels use photovoltaic (PV) technology to generate direct current electricity from the sun’s energy. A direct current flows in one direction and the voltage is constant. This makes it incompatible with home electrical circuits and most domestic appliances.
Solar inverters – also known as PV inverters – convert direct current electricity generated by solar panels into alternating current electricity. The direct current goes through a transformer that rapidly switches direction of the DC input back and forth. This lowers the voltage and creates AC output.
Besides converting solar energy into an alternating current, solar inverters typically perform several other functions, including:
- Monitoring the solar energy system and electricity production.
- Optimising energy output.
- Detecting faults in the system.
- Linking with computer networks.
- Feeding alternating electricity back to the national grid.
With solar battery storage systems, advanced inverters can be designed to operate without any help from the grid in the event of a power cut.
How Much Are Solar Inverters?
Solar inverters are usually included in the installation and cost of a solar energy system. But while solar panels have an impressive lifespan, the inverter system is unlikely to last as long and will most probably need to be replaced at some point.
Solar power inverters vary considerably in cost and can range anywhere from £500 to a couple of thousand pounds.
Factors influencing solar inverter costs include:
- Type of inverter.
- Potential power output of the inverter.
- Conversion efficiency of the inverter.
If you don’t know which type of inverter system your solar panels have, you can find out by contacting the installer or looking at your contract.
Types of Solar Inverters
The type of solar inverter your solar installation needs – and the cost – will depend mainly on how much power you need to meet your household requirements.
There are a few types of solar inverters. String inverters and microinverters are the most common.
String inverters, also known as central inverters, are the most widely used inverters. They’re also the oldest type of inverter, using tried and tested technology that’s affordable, relatively simple, and has been around for decades.
They’re called string inverters because they connect to a solar panel string – multiple photovoltaic modules linked end to end. A string inverter is installed near the electricity meter or consumer panel, on an exterior wall of your home or inside.
The direct current electricity generated by your solar panels is sent to the inverter, where it’s converted to alternating current.
How many solar panels that can be connected to a string inverter depends on the device’s input voltage rating. A string inverter usually works with five to 10 solar panels and has a lifespan of 10 years.
Advantages of String Inverters
String inverters have stood the test of time because they’re reliable, robust, and durable. They’re more affordable than microinverters because generally only one device is needed per installation.
If there’s a problem with a solar system, it’s often caused by the inverter. When there’s just one inverter, troubleshooting and repair is easier. No one has to climb onto the roof.
Disadvantage of String Inverters
String inverters equalise performance of solar panels. This means the inverter is only as efficient as the poorest performing panel in the solar array.
If one of your solar panels is shaded, dirty or damaged, a string inverter will only output the same amount of power generated by that panel.
When a panel gets a lot of shade, the solution comes in the form of an optimiser (more on this later). If a panel is broken, it needs to be repaired or replaced. If it’s soiled, you can clean it.
If a string inverter breaks down, the entire solar array will cease to work.
String Inverter Costs
A new string inverter for an average home costs around £500 to £1,500. The inverter is generally included as part of the complete solar PV system, so the type of inverter affects overall installation cost.
Solar panels can last upwards of 25 years. The shorter, 10-year lifespan of a string inverter means it will likely have to be replaced at least once. So the total cost of string inverters could be £1,000 to £3,000 over the life of your solar energy system.
Microinverters are most common with smaller, complex solar arrays. While a string inverter connects to a chain of solar panels, microinverters are attached directly to individual panels.
One device is mounted on the back of each solar panel on your roof, where the conversion of direct current to alternating current is completed at the source of energy generation.
Some microinverter models are designed so two or four panels can be attached to each device. Unlike string inverters, microinverters function in a parallel circuit, and they work well with complex solar arrays on multiple roof faces.
Advantages of Microinverters
Microinverters resolve many of the issues associated with string inverters. They’re more efficient and cost effective, with the entire output of each panel being converted to alternating current.
Unlike standard string inverters, the output of microinverters isn’t capped by the lowest-producing solar panel – they take full advantage of the electricity production of each individual panel.
And with one inverter per panel, the solar array is reliable – individual failures won’t hugely impact other parts of the system.
Disadvantages of Microinverters
Microinverters are significantly more expensive than string inverters and may be more suited for complex solar systems rather than a simple domestic solar array. A microinverter system needs more equipment than a string inverter. This means higher cost and more points of potential failure.
Microinverters are also harder to repair. A technician will have to get up on the roof, identify the faulty inverter, and then fix it.
On the upside, if there is a problem with one microinverter, the rest of the system will keep functioning and powering your home with solar energy.
Microinverters, which use relatively new technology, are typically more costly than other types of inverters. They range in price from £20 a unit to £100 a unit –10 to 30 percent more than a standard string inverter.
With the average solar PV system in the UK comprising 14 panels, this means the microinverter element of your solar installation would have accounted for upwards of £2,500 including work such as wiring.
However, the additional cost may be offset by more energy production. With a 25-year lifespan, microinverters can last as long as your solar panels, eliminating the further expense of a replacement inverter.
What Are Grid-Tied Solar Inverters?
Alternating current electricity produced by a grid-tied solar PV inverter can be exported to the grid as well as used to power your home.
These inverters deliver energy to your home directly from your solar system when the panels are generating sufficient power. They are able to switch to grid power when there’s not enough power.
Grid-tied PV inverters incorporate processing intelligence so they know when grid power delivery is necessary and when it isn’t. They range in price from around £400 to £950.
What Are Hybrid Inverters?
Hybrid solar inverters combine a string inverter and a power converter in a single unit. This facilitates storage of excess energy or, like a grid-tied solar inverter, feeding it back to the national grid.
The inverter element of the hybrid device turns direct current electricity produced by solar panels into an alternating current for use in your home.
If you have a solar battery storage system and use your solar panels to charge it, this needs a direct current and the voltage will need to be regulated.This is where the converter comes in. It regulates the energy at the right voltage and amperage to safely charge the batteries.
A mid-range hybrid inverter costs from £1,200 to £1,500.
Hybrid inverters are considered more reliable than a standard grid-tie inverter because they have a built-in battery backup system – you can still use your solar energy system during a power cut.
What Are Power Optimisers?
Like microinverters, power optimisers are attached directly to individual solar panels. They also offer many of the advantages of microinverters but cost slightly less.
The difference with a power optimiser is that instead of converting direct current to alternating current at roof level, it directs the direct current to a string inverter or hybrid inverter.
Performance of power optimisers can be monitored for each panel via an online portal.
As a rough guide, power optimisers cost around £40 a unit. This increases to about £180 per panel for smart solar systems.
Although solar power optimisers may increase initial costs of a solar system, the increased efficiency often means a good return on investment in the long term.
Why Do Solar Inverters Fail?
Solar inverters are more complicated than solar panels, with more things to go wrong.
Signs that a solar inverter might be failing include:
- Error message. An onscreen error message is a definite indication that something has gone awry. So are flashing status lights.
- Unexpectedly high energy bill. If the inverter isn’t producing enough power for your home, you’ll be pulling more electricity from the grid than usual.
- Solar battery charging failure. Some solar batteries are charged by electricity from the inverter. So, if the battery isn’t charging, that can be a sign the inverter isn’t working properly.
Over time, solar inverter components will wear out and the unit will need to be replaced.
Sometimes inverters may fail before their expected lifespan for several different reasons. These include:
- Poor installation including incorrect wiring.
- Incorrect sizing of the inverter to match the solar system, resulting in undervoltage or overvoltage.
- Rapid wear due to overheating when the inverter is subjected to high temperatures.
- Lack of maintenance.
Solar Inverter Maintenance
If your solar inverter system stops working, your home will no longer get the electricity generated by your solar panels.
This could result in a suddenly high energy bill because you’ve been using more grid electricity than you realised.
So it’s important to get the most from solar inverters and prolong their lifespan. This entails proper maintenance such as:
- Keeping the inverter cool. As an inverter converts electricity from direct current to alternating current, it gets hot. Sufficient airflow is necessary to avoid overheating.
- Ensuring the filter is clean. Keeping an inverter air intake filter clean prevents accumulation of dust and debris that can result in overheating.
Despite maintenance measures, an inverter may still develop problems that decrease performance or cause the device to stop working altogether.
If this happens, you’ll likely need to contact a reputable home solar installation company, who will have the technical expertise to either fix the inverter or replace it. Keep reading for more info on the best solar inverters.