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Choosing the Right Inverter

The inverter has the important job of changing direct current (DC) produced from the solar panels into alternating current (AC) so that it can be used in the house, the difference between one install company compared with another is at the design stage.

The best inverter for the job

At Harvest we don't send a salesman to your property, we send a designer who understands the best way to maximise your roof's potential and in doing this solar arrays can often be split, for example East/West.  The easy option is often to split the array evenly, half the panels on one elevation and half the panels on the other, however this is not always the best option, the West elevation may be closer to South than the East elevation so why not put more panels on the West elevation and take advantage of its southerly aspect. It is important at the design stage that the right inverter is specified for the job, especially in the case of an uneven split, so that it runs efficiently 90%+.

Many companies will use generic software which do not keep up with the constant changes and updates of inverters.  Because of this an older or outdated model will be specified rather than a newer, more efficient, better-suited model.  For this reason we check our system design by running it through the manufacturers' software.

How do I choose the best inverter for me?

Solar Inverters

Your array is designed to take into consideration the following factors:

  • Shading
  • Uneven or split arrays.
  • Efficiency checked with manufacturers software and found to be over 90%.
  • Individual monitoring of panels if needed.
  • Hybrid inverter needed for battery storage
  • Guarantees – length of a guarantee is no guarantee that the company will honour it. 

If the inverter is designed correctly for application then you are left with 2 more considerations, price and guarantees. Often the better the guarantee the more expensive the inverter and by the better guarantee I don't mean the longest guarantee. There are too many solar panel installers today who attempt to convince potential clients that their inverter is better because it has a longer guarantee. Guarantees are only as good as the manufacturer who is supplying the product. Basically if you get a 10-15 year warranty on an inverter and the company offering it are not in business in 2 years that warranty is not worth the paper it is written on. No company can guarantee its future, but not to take this into consideration would be a mistake.

We have installed almost every make and model of inverter on the market and although inverters are rarely changed due to faults, it does happen and not just to the cheaper end of the market, but also the more expensive German manufactured models. In our experience there has been one critical difference between manufacturers, their response time.  A leading manufacturer such as SMA will replace an inverter within 2-3 days, whereas a much less well known manufacturer can take as long as 6 weeks and in some cases not at all if they are not in business. At Harvest Cornwall we install a wide range of inverters, we are not tied to a particular manufacturer, but from experience we recommend inverter manufacturers that have proved themselves to us.

Where should inverters be installed?

Solar Inverter Installation

This point has been debated many times, and there are a few schools of thought.  The first is that the inverter needs to be as close to the solar PV array as possible in order to eliminate voltage drop, however manufacturers have proven that the drops are not significant even as much as 70 meters away.  With this in mind it would be perfectly fine to have the inverter out of the loft in a garage or even outside as the majority of inverters are now IP 65 rated for outside. The second school of thought is that the inverter should not be in the loft because many lofts are not well ventilated and the inverter could overheat making it less efficient, however it has been argued that this is the reason inverters have cooling fans. We will discuss the best option for siting your inverter during the survey.

How long do they last?

Inverters have few moving parts, but the general thinking is that there will be at least one change over the lifetime of the Feed in Tariff (20 years).