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Solar Inverters

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The heart of your solar PV system

Many people spend many hours wondering which panel they should choose and don’t give a thought to any other component of the system.

However the real heart of the system is the solar inverter, a very clever piece of kit which costs between £500 and £1200 on a typical small scale / domestic system (depending on size). A typical commercial-scale inverter (20 kW) can range between £1500 and £4500. For this sort of money it’s worth a read on what you are buying!

The role of the solar panel inverter

The panels generate DC (direct current) electricity. However the national grid and every electrical item in the house runs on AC (alternating current) electricity. The main task of the inverter is to convert DC into AC, synchronised with the supply voltage. It also has important safety features to protect your system and to protect engineers working on the national grid in the event of a power cut on the grid. Sounds simple but if you read on you will start to discover some of the clever bits.

Our inverters

We use a variety of solar power inverters, all of them market-leading. They are listed in the table below.

Overall, the best inverter on the market is probably SolarEdge, which uses power optimisers to optimise the performance of each panel and increases output by 2% to 25% over the life of the system.  We have dedicated a whole page to SolarEdge- click here to read it.

 

Manufacturer/ Origin Efficiency (domestic model) Warranty Monitoring Spirit Rating
SolarEdge (Israel) 98.8% 12 years SolarEdge Portal 10/10 The best inverter and monitoring system with individual panel optimisation, enhanced safety features and export limitation options.
SolaX (China) 97.1% 10 years SolaX Portal 10/10 Great quailty inverter at an excellent price, with UK-based support. Battery-ready upgrade available.
ABB (Switzerland) 96.5%

5 years (standard) 

10 years (extended)

Aurora Vision 9/10 A premium inverter from a multinational electronics company. Excellent aftersales service.
SMA (Germany) 96.5%

5 years (standard)

10 years (extended)

SMA SunnyPortal 9/10 A premium inverter from the most reputable inverter company.
Solis (China) 96.8%

5 years (standard)

10 years (extended)

Ginlong Monitoring 8/10 Good value inverter.
ZeverSolar (China/Germany) 96.2%

5 years (standard)

10 years (extended)

SolarCloud 8/10 Good value inverter. Owned by SMA.

Standard inverters

The best ‘standard inverters’ on the market are the Sunny Boy inverters, made by the German company SMA, as well as those made by the Swedish-Swiss company ABB. They typically come with 5 year warranties extendable to 25 years. Our standard package includes a warranty extension to 10 years. However, they come at a significant premium so it may be more economical to go with SolaX, a cheaper but still very high quality inverter.

If you read our guarantee you will see that we guarantee to investigate any fault with your system with no call out fee for five years. We do this with confidence – we really are not expecting to visit because we use high quality, well engineered, market leading inverters.

With a standard inverter, the system is optimised across a whole array of panels, and it therefore tends to be dragged down to the level of the worst performing panel. 

Micro-inverters and power optimisers

Note that you may come across micro-inverters and power optimisers. With these, every panel has its own inverter or optimiser, hence the term ‘micro-inverter’. SolarEdge make power optimisers and Enphase make microinverters, along with a few other manufacturers.

Micro-inverters and optimisers optimise the performance of each panel individually so they are useful to mitigate the effects of shading and allow for enhanced monitoring of each individual panel. However, they are considerably more expensive so whether to use them needs to be thought of carefully.

Fully automated operation

After sunrise, as soon as there is sufficient output generated by solar modules, the control unit starts monitoring the utility line voltage and frequency as well as the available energy in the panels. Once enough sunlight is received, the solar inverter starts feeding the utility transmission grid. Depending on the type of installation, a few watts of solar power will be enough do the job!

The inverter will now continue to work such that it always draws the maximum of power from the solar modules. This function is called MPPT (Maximum Power Point Tracking) and is carried out with a rate of accuracy of more than 99%! After dark, when the energy offered is no longer enough to feed the utility transmission grid, the inverter automatically cuts the connection to the grid and stops operating, of course with all settings and data being conserved.

Grid monitoring, safety cut out

Inverters need to meet minimum safety standards and conform to industry standard protection settings. This means that they need to monitor voltage and frequency and stop operating in case of irregular grid conditions (e.g. utility outage, interruption). If any protection setting is breached they stop the feed into the grid. This is important. In the event of a power cut engineers will work on the electricity transmission lines to find the fault. Obviously they can’t do this if your system is still pumping electricity into the grid.

The inverters also feature a high frequency transformer that ensures a galvanic separation of the DC side from the utility transmission grid.

Get in touch today for advice on the best solar inverter for your system.

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