When choosing a solar system for your business, one of the major components to consider is the inverter…or inverters. The inverter’s primary function is to convert the energy produced by the solar panels from DC (Direct Current) to AC (Alternating Current). Micro inverters consist of an inverter at each panel whereas a central inverter is a single unit that all the panels tie into. When deciding which is right for you there are three major considerations: Efficiency, warranty, and value.
Efficiency: Micro inverter manufacturers tout greater efficiency. Their reasoning is that duplicate solar panels do not produce the exact same amount of power. (Example: A low quality 240 watt solar panel can produce between 228 (-5%) to 264 (+10%) watts.) A central system is only as good as its weakest link, therefore the system will be less efficient. With higher quality panels the tolerances are much tighter and in some cases plus only ratings used, in these cases the weakest link argument is greatly discounted. Using the California Solar Initiatives (CSI) calculator to test this theory, we have found that there is no difference. CSI tests, rates, and approves all equipment used in order for a solar system to be eligible for a state rebate. To learn more about how they do this go here. There are three scenarios where micro inverters do excel over a central inverter, shading issues, solar panels on multiple planes of a roof, and when using cheap panels. A central inverter system works like a bank of batteries. If one panel is shaded it draws down the entire system. With micro inverters the draw down is limited to the effected panel(s).
Warranty: The leading micro inverter manufacturers are offering a 25 year warranty and claim they will last much longer than the typical 30 year life cycle of a solar system. Central inverters typically come with a 10 year warranty and typically last 15 years. A warranty is only as good as the company standing behind it. So do research on the manufacturer being specified. How long have they been in business, do they turn a profit, are they an industry leader, where do they manufacture their product? Enphase Energy, the market leader in micro inverters, was founded in 2006. SMA, the market leader in central inverters, was founded in 1981.
Value: The greatest value should consider the above and then weigh it with the price. On a typical residence, micro inverters cost 50% more than a central inverter. Given the price difference, we typically specify a central inverter unless the layout and/or shading issues warrant the added expense.