Choosing the Right Size Inverter for Your Solar Installation
Choosing the Right Size Inverter for Your Solar Installation
Inverters are typically not the first thing you think of when thinking about going solar, but they're an important part of every installation. How do you configure inverters in your system? What size do you need, and how do I implement one that's perfect for my solar installation?
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Do I need an inverter?
Yes! Inverters serve as the gateway between the photovoltaic system and the devices and appliances drawing energy from your system. They turn the DC output collected from your solar panels into alternating current AC, which is the standard used by all commercial appliances.
You will need an inverter to convert DC to AC to power most appliances and devices from laptop to microwaves. You typically need a solar inverter for any solar panel larger than five watts.
How are inverters configured in off-grid systems?
In off-grid systems, a charge controller will send the power to a battery bank and then an inverter will convert the DC to AC for the home. Off-grid inverters, known as stand-alone inverters, need a battery bank to function. When selecting off-grid solar inverters, it is essential that the output power of the inverter is large enough to support the loads of the system. Many off-grid solar inverters include a charger in order to replenish the battery.
Which is the best solar inverter for me?
If you have an off-grid system, you'll most likely be choosing between installing a pure sine wave inverter and a modified sine wave inverter.
Pure Sine Wave Inverters: Pure sine wave inverters are capable of producing smooth quiet, and reliable electricity to operate appliances and electronics without any interference. Like its name suggests, pure sine wave inverters produce current in a pure sine wave shape. Renogy sells a range of pure sine wave inverters of varying capacities to fit your solar installation and your energy needs. Renogy inverters also provide overload protection for both DC input and AC output to prevent damage to the components and the unit.
Modified Sine Wave Inverters:In modified sine wave inverters, the polarity abruptly switches from positive to negative versus a true sine wave. When looking at the wave, it has a stair-step, square pattern, where the polarity is flipped back and forth. That choppy wave can negatively affect more delicate, sensitive equipment. If you have medical equipment you need to power, such as a CPAP machine, you won't be able to use a modified sine wave inverter. Additionally, in many cases, you'll hear a hum with devices attached to a modified sine wave inverter. However, with simple devices and appliances, modified sine wave inverters typically do the job.
What can I run with a modified sine wave inverter?
If you're looking to save some money, modified sine wave inverters can be purchased and used in simple systems without sensitive electronics. If the electronic doesn't have an AC motor and isn't a delicate piece of medical equipment, you may be fine. Old tube tvs, water pumps, and chargers usually operate ok with a modified sine wave inverter.
Appliances like refrigerators, microwaves, and compressors that use AC motors won't run as efficiently on a modified sine wave inverter. Some fluorescent lights will also not operate quite as bright, and some may buzz or make humming noises.
What do I need a pure sine wave inverter to run?
- Newer TV's
- Sensitive electronics
- Appliances with AC motors: Microwaves and refrigerators
- Medical equipment, such as CPAP machines with humidifiers
- Laser printers
- Appliances with electronic timers or digital clocks
Your laptop may be ok with a modified sine wave inverter, although some claim that not using a pure sine wave inverter will shorten the lifespan of your laptop's battery.
What are pros and cons of using a modified sine wave inverter?
Pros:
- Less Money upfront: Modified sine wave inverters are typically cheaper than pure sine wave inverters, so if you're on a budget and you're only powering simple appliances, modified sine wave inverters may be enough to meet your energy needs.
Cons:
- Lower efficiency: Modified sine wave inverters are not nearly as efficient as pure sine wave inverters.
- Will not work with many appliances: As mentioned above, there are a variety of appliances you need a pure sine wave inverter to run, as TV's, microwaves, and inverters.
What is the best off-grid inverter?
If your budget allows, pure sine wave inverters are typically the best choice because they can be used to power nearly all appliances, are efficient, quiet, and safe. Renogy's pure sine wave inverters are equipped to meet the needs of your off-grid system.
How do you connect an inverter to a battery bank?
Inverters larger than 500 watts must be hard-wired directly to the battery bank. The owner's manual of your inverter will specify the cable size you should use. Cable size also depends on the distance between the inverter and the battery. It's always good to use the shortest length of cable that is practical. When connecting an inverter to a battery, we recommend using an overcurrent protection device, such as a fuse or circuit breaker, between the two devices.
AC and DC safety disconnects are also a requirement in all systems. In off-grid solar systems, a DC disconnect is installed between the battery bank and the inverter. This is used to switch off the current flowing between the two components and is important for maintenance, troubleshooting, and protection against electrical fires.
What size solar inverters do I need for my system?
Solar inverters come in a range of different sizes. Like solar panels, inverters are rated in watts. Because your solar inverter converts DC electricity coming from the panels, your solar inverter needs to have the capacity to handle all the power your array produces. As a general rule of thumb, you'll want to match your solar panel wattage. So if you have a watt solar panel system, you'll need at least a watt inverter. Need help deciding how much solar power you'll need to meet your energy needs? Use the Renogy solar calculator to determine your needs.
For more information, please visit how to choose solar inverter.
Renogy has pure sine wave inverters ranging in size from 700 to watts. Inverter chargers are also a great option for those living off-grid who may also connect to shore power occasionally. In addition to converting DC to AC, the Renogy W Pure Sine Wave Inverter Charger can charge and maintain a battery bank when connected to shore power.
Conclusion
If you live in a remote area or on the open road without reliable and affordable access to the grid, off-grid solar can be a great way to meet your energy needs. Having an understanding of how inverters are configured and used in off-grid systems will set you on the right path toward building a safe, efficient, and powerful solar installation to meet all your energy needs.
How to choose the right solar inverter
Choosing the Right Solar Inverter
This guide will help you to choose the best solar inverter for your project. Use this handy reference table to compare the facts. Quickly see the difference in features, performance, warranty and more. Make an informed decision so you know what you are buying. However, these products are ever-changing, with new models or capabilities being added all the time. We'll do our best to keep you up to date with the industry.
TYPE
STRING
STRING + OPTIMIZER
MICRO-INVERTER
HYBRID
GRID-TIED
Yes Yes Yes Yes OFF-GRID
No No No Yes BATTERY READY No No No Yes RAPID ROOF
SHUTDOWN Optional Integrated Integrated Optional or Integrated
PERFORMANCE
IN DIRECT SUN
Up to 98% Efficiency about 2% more about 2% more Varies SHADE
MANAGEMENT
Each string Each panel Each panel Varies PANEL OUTAGE
Affected string non-operational Each panel operates independently Each panel operates independently Varies MONITORING Whole system or each string Each panel Each panel Varies
WARRANTY
STANDARD
10 years 12 years 10 to 25 years 5 to 25 years, varies by model WARRANTY
EXTENDED
20 years 25 years N/A 20 years
COST Most economical Add 6% to 10% to system cost Add 6% to 10% to system cost Add 10% to 25% to system cost
COMMON
BRANDS
SMA
Fronius
Delta
SolarEdge
Tigo Energy
SMA
Fronius
Delta
APSystems
Chilicon
Enphase IQ8
Generac PWRcell
Outback Power
Panasonic EverVolt
Schneider Electric
SolarEdge Energy Hub
Sol-Ark
WIRING
CONCEPT Panel output cables are wired together to form a string, up to a dozen or so panels. Inverter has input for 2 to 4 strings. The inverter then combines the output and converts to AC power connected to the electrical box.
Panel output cables are wired to a small optimizer device mounted to the back of each panel. The optimizer's are then connected together to form a string, usually 8 to 15 panels. Inverter has input for 2 to 4 strings. The inverter then combines the output and converts to AC power connected to the electrical box.
Panel output cables are wired to a small micro-inverter mounted to the back of each panel. The micros are then connected together to form an AC circuit, with up to 11 to 16 panels. Each AC branch circuit can then be combined, or wired to it's own circuit breaker connected to the electrical box. Varies by model. Similar to String or string + optimizer or micro-nverters wiring.
What to know about solar inverters
There are FOUR basic types of solar inverter: String, String + Optimizer, Micro-inverter, and Hybrid.
A grid-tied, string inverter is the most economical approach. Works just fine in direct Sun when shade is not an issue. Multiple strings, or groups of panels, are wired together, and then connected to the inverter. Each string operates independently. The string inverter may need replacement in 15 to 20 years. Ideal for ground-mounted systems or buildings where rooftop shutdown is not required.
A string inverter with Optimizers has a small device added to the back of each panel to "optimize" performance. Each panel operates independently, it can be monitored, and includes rooftop shutdown capability. Optimizers help minimize shade losses and improve overall performance.
Micro-inverters also adds a device to back of each panel to "optimize" performance AND convert from DC to AC power. Each panel operates independently, it can be monitored and includes rooftop shutdown capability. Micro-inverters help minimize shade losses and improve overall performance. The smaller electronics have a longer lifespan, and a brand like Enphase has a 25 year warranty.
Finally, a Hybrid inverter can work both on-grid, or off-grid with optional batteries. The solar panels and storage batteries are connected in one unit. The hybrid inverter also has an internal power transfer switch to deliver power during an outage. Some customers buy a hybrid inverter to be battery-ready and future-proof the system in anticipation that battery prices will decrease over time. Can add rooftop shutdown or optimizers as needed. Some hybrid inverters even let you connect a fuel generator as another power source to charge your batteries and power your home or business.
The value of good design
Most of the solar kits include an up-front design in the price. We want to make sure you get the right kit, with the right parts, for your project. The design covers topics like the power consumption, system sizing, the electrical connection and the structural mounting. Once the design is complete and the order placed, we will prepare a custom permit plan blueprint for the project. You you can provide the plan to the local building authority and utility for net metering approval. This value-added service is unique to SunWatts. The solar design can be ordered separately to get the project started. Then you will get credit for the design fee with solar kits that are 5kW size or larger.
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