Calculate solar panel output

[SolTex]

can I ask one more question before you leave? If my installer would have installed 1800w micro inverters instead of 1500w inverters would I have the capability of generating more than 9000w with the 24 455w panels and 6 miceo invertesr?

Yes, increasing the "size" of your inverters would allow your system to generate more than 9000W. HOW MUCH more depends on a number of factors.

With the bigger inverters, you would be close to a 1.00 DC/AC ratio. The only way you could utilize the max capability of the bigger inverters would be for your panels to actually output their STC rating. This almost never happens in the real world. Most system owners are lucky if they ever see 80% of the STC rating out of their panels. Panel DC output is almost always reduced below STC levels by geographical location, mounting azimuth and tilt angle, snow, clouds, dirt, shade, bird droppings, leaves, ambient temperature, age of panels, etc.

The reason most installers shoot for a 1.25 DC/AC ratio is because over sizing the panel output in relation to the max inverter output provides the most advantageous return on dollar spent. Plus, inverters like to work hard. They are most efficient when running close to max output.

If you want more power output from your system, the best way to do that would be (as you have already mentioned) to add 4 more panels and another 1500W inverter. This would increase system output and keep the DC/AC ratio at a favorable number.

All of the above is only my opinion. TIFWIW

[alfie1111]

OK, I'm out of here. Good luck.

can I ask one more question before you leave? If my installer would have installed 1800w micro inverters instead of 1500w inverters would I have the capability of generating more than 9000w with the 24 455w panels and 6 miceo invertesr?

[alfie1111]

However, the convention in PVWatts is to input the DC kW of the solar panels not the inverter. As a default PVWatts uses a DC:AC ratio of panels to inverter of 1.2 which is what you have. I could not be clearer that you have a 10.8kW system by the convention used in the solar industry. Give that a try.

k systemthat under no cirstances can it generate more than
so the industry is set out to screw the consumer? you are sold a 10.8k system that can not generate more than 9k even under perfect conditions. I know when I looked into installing a wind turbine I was told my inverter should be 15% larger than the rated output of my wind mill.

[RichardCullip]

well i live in pei canada the pv calculator says 11mw with a 9k system. I paid for a system that was $ per watt. Should I have a system that would come close to what I paid for of should I ged 10% less?

However, the convention in PVWatts is to input the DC kW of the solar panels not the inverter. As a default PVWatts uses a DC:AC ratio of panels to inverter of 1.2 which is what you have. I could not be clearer that you have a 10.8kW system by the convention used in the solar industry. Give that a try.

[alfie1111]

well i live in pei canada the pv calculator says 11mw with a 9k system. I paid for a system that was $ per watt. Should I have a system that would come close to what I paid for of should I ged 10% less?

Let me ask a simpler question. If I go to the hardware store and buy a 2x4x8 would It be safe to assume a 2x4x6 would do the same thing when i get home?

[alfie1111]

For grins, I modeled a 10.8kW set of panels with a 9kW inverter (1.2 DC:AC ratio) on my roof top in Poway, CA using PVWatts The calculator suggests that I would get 19,225kWh/year with an expected range from 18.479kWh to 19,346kWh.per year.

Not sure of your panel orientation and location but you might be surprised by what a system comprised of 10.8kW panels with a 9kW set of inverters could provide on a yearly basis. The 9kW set of inverters might not be the limiting factor you seem to think they are.

well i live in pei canada the pv calculator says 11mw with a 9k system. I paid for a system that was $ per watt. Should I have a system that would come close to what I paid for of should I ged 10% less?

[RichardCullip]

yes a 10.8kw system should cover my 13mw usage but i can not generate 10.8kw as my inverters will only out put 9k

For grins, I modeled a 10.8kW set of panels with a 9kW inverter (1.2 DC:AC ratio) on my roof top in Poway, CA using PVWatts The calculator suggests that I would get 19,225kWh/year with an expected range from 18.479kWh to 19,346kWh.per year.

Not sure of your panel orientation and location but you might be surprised by what a system comprised of 10.8kW panels with a 9kW set of inverters could provide on a yearly basis. The 9kW set of inverters might not be the limiting factor you seem to think they are.

[alfie1111]

IMO the solar seller lied to you about what you will need and what you are getting.

And this is what info I was trying to find out thank you

[SunEagle]

"Worry about whether it will generate enough to cover your overall needs" this is what is was trying to figure out, I was told i would need a 10.8k system to cover my usage but as far as I can figure out I have a 9k system.

IMO the solar seller lied to you about what you will need and what you are getting.

[alfie1111]

Most people I know would describe your system as a 1.82kW system (based on your four 455w panels). Your 1.5kW inverter will be a determining factor, along with orientation of panels, weather conditions, the area you operate those panels and some other conditions in how much electricity will be generated daily, weekly, monthly and yearly.

You need not obsess over how to describe your system. Worry about whether it will generate enough to cover your overall needs

"Worry about whether it will generate enough to cover your overall needs" this is what is was trying to figure out, I was told i would need a 10.8k system to cover my usage but as far as I can figure out I have a 9k system.

[J.P.M.]

Im not sure why I need JPM suggestion has absolute nothing to do with my original question

so you know here it is again

How are system rated? do I use panel out put or inverter output? I have 4x455w panels but my inverters only put out 1500w is this a 1500w system or a 1720w system?

Panel output in STC W is the common way of describing PV panel and system nominal size.

See and (re)read my 03/26/23 post of 0931 hrs. for how systems are described and rated.

Otherwise download a free PDF of "Solar Power Your Home for Dummies" from the net. It may clear things up for you.

I'll be with SolTex if you need me.

Good luck.

[RichardCullip]

How are system rated? do I use panel out put or inverter output? I have 4x455w panels but my inverters only put out 1500w is this a 1500w system or a 1720w system?

Most people I know would describe your system as a 1.82kW system (based on your four 455w panels). Your 1.5kW inverter will be a determining factor, along with orientation of panels, weather conditions, the area you operate those panels and some other conditions in how much electricity will be generated daily, weekly, monthly and yearly.

You need not obsess over how to describe your system. Worry about whether it will generate enough to cover your overall needs

[SolTex]

OK, I'm out of here. Good luck.

[alfie1111]

Strange how my electric bill was $259.00 last month and the calculator comes up 2mw short

Im not sure why I need JPM suggestion has absolute nothing to do with my original question

so you know here it is again

How are system rated? do I use panel out put or inverter output? I have 4x455w panels but my inverters only put out 1500w is this a 1500w system or a 1720w system?

[alfie1111]

I would suggest taking J.P.M.'s suggestion and running your numbers in the PVWatts calculator. Try inputting your present system and see what you get. You may be suprised to find that regardless of what the fast-talking sales person said, you were in fact sold a system that will meet your requirements. If, OTOH, if the calculator says your present system falls short, you can run it again with 4 more panels and another inverter and see how that comes out.

You don't mention your geographic location or any specifics about your installation. Just as a comparison, I put what numbers you have stated up against our system. We live in West TX where the annual solar radiation numbers are very favorable. Below in the little chart I compare my system to yours:

Annual consumption: (mine) 26,000 kWh (yours) 13,000 kWh
System DC size: (mine) 15,200 W (yours) 10,800 W
System AC size: (mine) 11,800 W (yours) 9,000 W
DC/AC Ratio: (mine) 1.29 (yours) 1.20

You can see that my annual consumption runs about twice what you consume. Yet your system (AC rating) is about 75% the size of mine, so under suitable conditions should have no problem supporting your annual consumption.

When I plugged my system into PVWatts (BEFORE we signed the contract) it predicted we would offset our usage 110% over the course of a year. So far, after a year of operation, we are running well ahead of the prediction. I think the calculator can produce some pretty reliable results, as long as the inputs are correct and accurate.

Strange how my electric bill was $259.00 last month and the calculator comes up 2mw short