The following are a few important facts that you need to keep in mind before you purchase a solar inverter:
Check the Size
First off, consider the amount of power that you need to run your household. Determining the appropriate off-grid inverter size that’s right for your home is pretty simple and requires only that you make a list of all the appliances that you’ll be using around the house.
Then, calculate the wattage of all the different appliances and lights put together to figure out how many watts your system will need to generate in order to power everything at once. Of course, you probably won’t have everything running at the same time, but aggregating everything like this is the best way to get the most out of your solar system.
Remember to include the voltage that each appliance requires to run smoothly. The average appliance typically runs on 120Vac, whereas something as complex as a good pump might require up to 240Vac.
Consider Pure Sine Wave Instead of Modified Sine Wave
We won’t go into how pure sine wave inverters work in this article, as that would require a whole other post. However, we can tell you that they provide a cleaner power output than a modified sine wave inverter.
However, some people opt for modified sine wave inverters anyway because they’re a much cheaper option but they end up with low-quality power output as a result.
Pure sine wave inverters, on the other hand, provide excellent quality power output that’s comparable to a power grid (and in some cases even better).
Also, modified sine wave inverters have been known to negatively affect the performance of certain appliances like pumps, compressors, and motors that just wear out quicker than they’re supposed to. It can also damage computers to the point of complete breakdown, while TVs and radios often end up with static background noise or develop poor audio and video quality.
That’s why we highly recommend that customers go for pure sine wave inverters to avoid these and other problems. Even if you have to save a little more for them, it’s worth the wait because you know they’ll help extend the lifespan of your appliances.
If you want to know what the difference is between a pure and modified sine wave inverter, simply look at its total harmonic distortion (THD) rating. This is usually written on the inverter’s spec sheet and tells you what the power quality output of the inverter is.
Look at the Technical Specs
The following is a list of important technical specs to look out for when making your purchase:
- Efficiency – This basically refers to the maximum amount of battery power that the inverter will be able to deliver to your home appliances. Ideally, you want your inverter to have a maximum efficiency rating of 94% to 96%.
- Self-Consumption or No-Load Current Draw – Even when it’s sitting on standby, your inverter will continue to consume power. For the best results, make sure you go for an inverter that has low power requirements.
- Surge Capacity – No matter how efficient your system is, short-term overloads can happen. You need an inverter that has a high surge capacity so that it doesn’t trip when this happens. Also, keep in mind that certain appliances like the fridge require up to 3x of their normal energy requirement to even power up.
- Battery Charger Output – A thoughtfully designed off-grid inverter should come with its own battery charger that you can use along with a backup generator to keep the lights on during the cold winter months. The battery charger for a solid quality off-grid inverter will have a rating of about 50-100 amps DC to keep you going.
- Temperature Range – Whatever you do, don’t store your inverter in an area that experiences extreme temperatures because they are very sensitive to extreme heat.
- Warranty – The standard warranty period for an inverter starts at one year, but this can go up to 3, 5 and even 10 years if the manufacturer is willing to provide an extension.
- If you want to find out how your inverter measures up based on the above mentioned technical specs, simply look at the product’s spec sheets, or consult with a specialized solar technician to help you choose a good quality inverter.
Depending on the inverter you end up choosing, you may need to purchase a few extras, such as:
- Battery Charger – This will keep your system running even when there’s no sun for your solar panels to draw energy from. These can also double as inverters when needed, and they work by drawing power from a backup AC generator.
- Grid-Tied Capability – If you’re considering a grid-tied setup with backup battery power, then it might be worth it to consider a grid-tied inverter with the ability to send power to a central grid.
- Automatic Generator Start – While this particular function comes as a standard feature of some inverters and charge controllers, yours might require one that comes as an extra attachment.
- Read Up on the Manufacturer – To make sure that the product you’re purchasing is of high quality, do your research on the manufacturer and find out what kind of reputation they have. At the end of the day, inverters are a long-term investment that you should purchase from a reliable manufacturer.
Check for UL Listings and Certifications
For the purposes of code compliance and safety, off-grid inverters need to be certified according to the law.
For example, home inverters require a UL 1741 listing, while boat and RV owners need to carry a UL 458 for their mobile inverters.
Inverters that are used for emergency purposes require a KKK-A-1822E certification, and you’ll need a UL 1778 in order to enjoy an uninterruptible power supply.
If you’re outside of the US in a place like Canada, you’ll need to have a CSA 107.1 standard certification, and for that outside of North America, there’s the IEEE 1547 standard certification which is internationally recognized.
Check the Price
As with anything that you purchase, the price will play a huge role in the type of inverter that you choose, and of course, you get what you pay for. Oftentimes, the pricier a model is the more features it has.
Also consider the price of the components required when installing the entire system, including circuit breakers, mounting plate, remote control etc., and don’t be afraid to shop around to compare prices too!