String inverters are a solid and time-tested technology that is cost-effective too. Each panel is wired in series (a string), forming a circuit. The single inverter is installed near your utility meter, either at the side of the building or inside the garage. For sites with full sunlight, string inverters are a cost-effective solution. For sites where temporary shade is caused by trees or nearby structures, a string inverter may not be your ideal solution. With a string inverter, temporary shade on the string, even if just one panel, reduces production for the entire system.
How String Inverters Work
- A single unit, usually mounted either at the side of a building or in a garage, that functions for all of your solar panels.
- All solar panels connect together in “series wiring”.
- Work well for most applications and are a good value. A string inverter can accommodate future system expansion, if planned for during the original system design.
- Maximum power point tracking (power harvesting) is performed at the system level, not the panel level, resulting in lower system production.
Best For Sites with Minimal Shading
- String inverters are not optimal for applications where solar panels receive transient shade from immovable objects such as nearby trees, chimneys or adjacent structures.
Not Ideal for 3+ Roof Orientations
- String inverters are not optimal for installations where solar panels must be mounted on multiple roof sections facing 3 or more different directions.
System Level Monitoring
- String inverters allow you to monitor system performance and track historical production but do not allow you to view individual solar panel output, only the sum performance of the system.
- View production on the a Smartphone, Tablet, or Computer
10 Year Warranty
- String inverters typically carry a standard manufacturer warranty period of 10 years. Extended warranties are available at an additional cost.
|Max Solar DC Input||4.35 KW||8.00 KW|
|Main Main Panel Size Required||100 Amps||200 Amps|
|Max AC Output||3.8 KW||7.7 KW|
|Compatible with SPS Switch||✓||✓|
|Warranty||10 Years||10 Years|
Max Solar DC Input: The maximum solar array size recommended before it’s more cost effective to go with a higher efficiency inverter. DC input is: number of panels × rating of the panel.
Min Main Panel Size Required: The inverter requires your main service panel to be of a minimum size. YES provides in-house main panel upgrades to allow for a higher inverter capacity when installed with a new solar system.
Max AC Output: The inverter coverts DC to AC. This value is the maximum “useable” electricity that can be produced.
In all SMA models, the DC input can be larger than the AC output. This is array oversizing.
Example: Suppose you install 14 LG 300 panels with a SMA 3800TL inverter. This creates a DC input of 4.2 KW. While the inverter’s AC output capacity is 3.8 KW, which is below the DC input, to maximize return of investment, it is best to go with the SMA 3800TL rather than the 7700TL.
Explanation: The manufacturer tests each panel in the lab in perfect conditions, tested free of dust, dirt, bird droppings, leaves, and shade. Under these conditions, the LG 300 has a peak production of 300 watts. However, in the”real world”, an LG 300 will peak at 273.5 watts (according to the California Solar Initiative). This creates a maximum DC input of ~3.82 KW.
If all your panels are facing the same direction, you may experience clipping with an oversized array. This peak will only occur during the summer months and for a small duration of time. During this time, the SolarEdge inverter will output 3.8 KW AC. When clipping is not happening, you gain more production with a smaller-size inverter, maximizing savings. While you may go with a higher-capacity inverter, the additional cost of going with a higher-capacity inverter is much greater than the marginal benefit of slightly extra power.
Multiple Roof Orientations
Oversizing your array is beneficial if your solar system faces two different orientations (directions). Each direction’s production will peak at a different time of the day. The combined production may be less than the inverter’s AC output capacity.
Solar systems are grid-tied. Regulations require solar systems to shut down during utility outages. Off-grid batteries that follow regulations are available, but are expensive. When the sun is up and the grid is down, the SMA Secure Power supply allows you to draw up to 1500 watts of electricity directly from your panels. This is enough to charge small devices such as cell phones or small radios.
Going Solar with SMA
Our energy consultants will help size your system, including determining which combination of solar panels and inverters that maximize production, reliability, and savings.