String inverters vs micro inverters: which is right for you?
Posted by Zoe Bodinetz on 3 February 2020 at 1:41 pm
The electricity generated by solar panels is in ‘Direct Current’ (DC) form, which needs to be converted to ‘Alternating Current’ (AC) form before it can be used by customers. A system of solar panels will need an ‘invertor’ to change DC to AC, and there are two main types: String-Inverters and Micro-Inverters. It is important to know the difference between these systems and understand what will work best for you before buying a solar panel system for your home.
What’s the difference?
String-Inverters are connected to the series of solar panels and convert the entire DC output of the series to AC output. Micro-Inverters are attached to each individual panel in the system and convert the individual DC output to AC at the solar panel.
String inverter system:
Which type is right for you?
String-inverters are typically cheaper, since you only need one for the entire system, and the single inverter means there’s a smaller chance of circuit failure. The inverter doesn’t need to be located close to the solar panels, so resistance to heat/humidity is less of an issue. However, because of the system set up, the total power output is determined by the lowest generating panel. This means that if one panel is in shade, then the total output voltage will be equal to the shaded panel. Whilst this can have a significant effect on the power output of your panels, if your property does not have a problem with shading, it should not put you off using a string inverter system. If your panels are facing multiple angles, or your property has a lot of shaded areas, then this system is unlikely to be right for you. String inverters typically cost between £500-£1000 with a roughly 10 year warranty
Micro-inverters are located closer to the solar panel system, so need to be designed to be resistant to humidity and heat. Because of this, and the need for multiple inverters, micro-inverters are the higher cost option. Multiple inverters also means there is a higher chance of circuit failure. However, since the power output is not sensitive to voltage differences between panels, a micro-inverter system tends to have a higher overall electricity yield. Using this type of inverter can increase the output of the panels by up to 30%.This higher output, over time, will compensate for the higher cost of the system. Micro-invertors cost between £65-£85 per inverter box, so depending on the number of solar panels, you can expect to pay about £1500 for a full set-up.
Are there other options?
Hybrid inverters have recently emerged as a method to store solar energy by having a battery charger and converter built into the inverter system. Although more expensive to install than standard inverter systems, stored energy can be helpful for household systems to allow energy use through the evening. However, for businesses that are only operating during daylight hours, a standard string-inverter setup is the more economical choice. These types of inverters require more room and the battery life tends to only be about 7-15 years.
Power optimisers are another new technology that can be used to improve the output of a string-inverter system. They work by ‘fixing’ the voltage of the generated DC electricity of each panel, before it is sent to the central string-inverter, which works to increase the total power output of the system. Although they don’t increase the power output as much as microinverters, they cost less than microinverters to purchase and install, so can be considered a good compromise for homeowners looking to improve their solar panel system for a smaller cost.
In conclusion, it really depends on how much you’re wanting to spend on your set up, but its also worth considering whether the extra expense is worth it in your specific case. If you don’t have a problem with shading, then you probably don’t need to pay extra for a micro-inverter set up. If you don’t need to use energy from your solar panels at night time, then it’s probably not worth spending money on a hybrid inverter. On the other hand, increases in system efficiency will often pay for themselves over time, so you can think of the extra expense as an investment.
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