As an Amazon affiliate, we earn a commision from qualifying purchases.
“What size inverter do I need for solar panels?”
Well, we have some handy guidelines on solar inverter sizing in this article plus some general tips to help you get your solar inverter dimensions right the first time.
Let’s dive right in:
What size inverter do I need for solar panels – what you should know
Choosing the right size of inverter for your solar panel array need not be an uphill task.
Of course, it involves some calculations because what you want is to determine the maximum power your solar inverter is likely to be handling safely and efficiently but these are going to be pretty simple maths.
In short, to get the correctly sized inverter for your PV system, you must know the following beforehand:
- The DC rating of the solar photovoltaic installation.
- Your typical operating conditions (climate and location).
Let’s get down to the specifics now:
What size inverter do I need for solar panels –start with this
As mentioned, your choice of an inverter will be first (and perhaps most importantly) determined by your current solar array’s DC output.
In fact, the general rule of thumb is to have your inverter sized similarly to the watts your solar PV system outputs.
In sum, you should do just fine if you order an inverter that matches your solar system’s array capacity!
That’s a simplified look of things and it’s better to take into account all vital factors when doing the inverter sizing, because you want to make the best decision.
Pay attention to the following details to help you choose the perfect inverter size.
Understand about the all-important array-to-inverter ratio
Whichever way you approach it, you have to consider the vital array-to-inverter ratio.
So, what is exactly is this and why is it important?
Now, this is nothing else but the relationship between the array nameplate rating (in DC watts) and the inverter nameplate rating (in AC watts).
To arrive at it, take the DC rating of the solar array and divide it by the highest AC power output of the inverter you have in mind.
For instance, if you pair a 5 kW array with a 5000 W inverter, your array-to-inverter ratio will come to 1 (1 kW is 1000 watts).
This changes to 1.2 if you’re working with an array of 6 kW (on the same 5000 W inverter).
How is the DC-to-AC ratio important?
Now to the ratio’s importance…..
A reminder first: Since your inverter will be handling DC electricity made and sent to it by your solar PV system, it’s crucial that you select an inverter size that can handle and convert this load to AC energy.
You cannot, therefore, afford to pick the incorrect solar array-to-inverter size.
Fortunately, most manufacturers publish guidelines and you will notice that many recommend the ratio not to be higher than 1.55 (the range is typically between 1.15 – 1.25).
The answer to your question “What size inverter do I need for solar panels” starts with getting the ratio right.
Here is the thing:
In many cases, a DC-to-AC ratio of 1 is accepted, and the reason why we previously mentioned that you should ensure that the total capacity of the solar panels (in an array) is equal to the energy capacity written on the inverter.
In this scenario, zero energy is lost (nearly!) as a result of the system delivering more power than what the inverter can handle.
But is this cast on a stone?
Keep reading to discover if you have some room for maneuver (and whether you can go for a mightier inverter).
How to choose inverter for solar system – can I oversize/oversize my inverter?
We continue with our discussion and we want to study if you can safely oversize your solar inverter as well as the result of installing an undersized unit still with the array-to-inverter ratio in mind.
Now, an array-to-inverter ratio that is higher (you buy a smaller sized inverter) than the stated threshold could be okay for your solar power system if the solar panels won’t produce their maximum rated power output.
Be careful, however, because you could experience clipping problems (solar panels overwhelming your inverter) if you go too high.
Likewise, array-to-inverter ratio that is lower (the inverter is larger) could work as well but not when you have oversized the inverter a lot as it won’t operate efficiently.
More on Oversizing solar inverter (undersizing PV array)
Over-sizing a solar PV inverter is hooking an inverter with a higher rated AC operational output to a PV system with a lower DC capacity.
To illustrate, you could buy a 5000 Watts inverter for a 3000 watts solar system.
In a nutshell, you have the funds and choose to invest in an inverter that is more powerful than your PV array.
But is this a reasonable approach?
The thing is I can’t find any sensible reason (economic or otherwise) of spending bucks on something that I may never use for eons to come.
That said, I see some installers insisting that this feature allows the upgrading of your solar array easily if the need arises in the future.
More on undersizing solar inverter
Inverter undersizing (or solar panel PV panel oversizing) means running panels with more DC power than the inverter is rated for.
Here comes a small example:
If you have connected a system producing 6kW of DC power to your 5000W inverter, you effectively oversize it by 20% (1.2).
Exceeding this setup should truly bring no problems since solar systems hardly run at the maximum 6kW (it only comes up momentarily), as long as your system is appropriately designed.
As a result, there’s an economic benefit in overloading solar inverters since the 5000w inverter is less expensive than the 6000W one.
Keep in mind that the rule of thumb when it comes to inverter ‘overclocking’ is to never stretch your inverter capacity by more than 30% (the solar panel array output shouldn’t be more than 1/3 higher).
Consider the climate and location
Professionals may propose an undersized inverter unit if they feel that there is lower solar irradiance (amount of solar radiation/unit area) than expected.
That is mostly caused by factors like the location, climate, and even the way your solar panels are installed.
Ultimately, you stand to save on inverter costs if you live in low-irradiance locations such as Seattle.
Although this is not a matter of life and death (like the ratio), we encourage you to do a bit of research and find out the amount of solar irradiance in your area to be sure.
When planning and setting up your solar panel system, the size of your solar inverter will have a major say in the final electricity output.
This article has provided you with some of the information you will require to choose the right inverter size for your solar panels.
You should also seek advice from professionals, if necessary.
MORE SUGGESTED READING: