With so many options on equipment, it is easy to get lost in the decision making process. One of the most common customer questions is the difference between microinverters and a system like SolarEdge that incorporates DC optimizers with a string inverter.
First, let’s look at the ways these two systems would be the same.
- Both SolarEdge and microinverters will maximize the power from each individual solar module with maximum power point tracking (MPPT) technology. Having an MPPT device at each solar module helps mitigate shade and orientation issues that can occur with the standard string inverters.
- Another common element is that both SolarEdge and microinverter systems will provide module level monitoring so you can see how each solar module is performing individually.
- Both systems also meet the 2014 NEC Rapid shutdown requirements in that if the system is shutdown with the disconnects that are accessible at ground level, the conductors from the roof will not be energized.
So, how are microinverters and SolarEdge different? It’s all about where the power is converted from AC to DC. The solar modules produce DC power and a microinverter converts that DC power to AC power at the solar module. In a SolarEdge system, there are DC optimizers that do the maximum power point tracking at the module but they don’t convert the power to AC. The “conditioned” DC power flows in the conductors that come down from the roof and it is converted to AC power at the central inverter which is typically installed near the main service panel of the building.
Now for the fun part…. Which one is best? Everyone in the solar industry has an opinion and the bottom line is you have to decide for yourself. Let’s look at some of the factors that will help you make this decision.
The cost of the whole system needs to be considered in this.
When buying microinverters, you will pay for the microinverters, the monitoring system and the trunk cable (which is a separate part for some brands and not others).
When purchasing the SolarEdge system you will buy the DC optimizers, the string inverter and possibly a monitoring option depending on how you want the monitoring to operate.
The individual microinverters will cost more than the DC optimizers (you are paying for all the DC to AC conversion electronics in every microinverter). The monitoring equipment is typically the same cost for either system. Then with SolarEdge, you have to buy the inverter.
The result is the total system cost on microinverters less than SolarEdge if you are doing a small system (under 3.8kw) and microinverters cost more than SolarEdge if you are doing a larger system (over 3.8 kw).
With both systems, you are mounting a device at each solar panel (either to the solar racking or the panel frame) so that part is the same.
With microinverters you will need a junction box on the roof to make the transition from the trunk cable system to the conductors that will take the power down to your main service panel. These conductors are standard AC power so there are no special rules in the NEC code on how they must be installed. With a smaller microinverter system, you will be able run the conductors to go straight to a circuit breaker in the main service panel (minus possible city or electric company requirements on the need for a separate AC disconnect). If it is a larger microinverter system you will likely want to install an AC subpanel to combine your branch circuits. Microinverters are typically limited to branch circuits of 20 amps (typically 12-17 modules). This AC subpanel can also a convenient place to install the circuit breaker required for your microinverter monitoring system.
For SolarEdge, you can use MC4 compatible connectors on the roof for each string (typically 24-25 modules) then go into conduit. You will have higher voltage DC power flowing on the conductors going to the inverter. If these conductors run inside the building NEC requires that they be in metal conduit before the first readily accessible disconnect which is usually the one integrated into the inverter. Then the SolarEdge inverter is mounted on a wall and will feed a circuit breaker in the main service panel.
These differences in installation are minor which means there is not much difference in difficulty or cost of installation on either system.
Both the microinverters and the SolarEdge DC optimizers are designed to be installed under the solar modules so in either case, all you can see on the roof is solar modules.
With SolarEdge, there will need to be an inverter mounted on a wall somewhere which would not be required with microinverters which means a microinverter install would have a cleaner look.
Warranties are provided by all the manufacturers to cover equipment failures but the failure rates vary and not all warranties are created equal. The things to consider about warranties are the length of the warranty, what the warranty covers and the longevity of the manufacturer.
Microinverters are more complicated than DC optimizers because they are converting DC to AC. As a result, the microinverters have a higher rate of failure. Microinverters warranties vary between 10 to 25 years depending on the brand. The shorter warranties can typically be extended to 20 or 25 years. Some microinverter manufacturers do not cover labor to replace equipment so that is something to look into before purchasing. Also, the manufacturer of the most popular brand of microinverters has yet to show a profit after many years in business so you might consider whether or not they will be around to honor their warranties in the years to come.
The SolarEdge DC optimizers have a 25 year warranty and the inverters have a 12 year which is extendable to 20 or 25 years.
This is where the SolarEdge system really shines.
Because the power is not converted to AC at the module level, SolarEdge has an advantage. The efficiency on the latest SolarEdge HD inverters is 99% compared to the typical microinverter efficiency of 97%.
So in the end, you will get more power out of the same modules with the SolarEdge system versus microinverters. This 2% increase in output can really add up over the 25 year life of a system.