The PVWatts loss numbers are a bit conservative, most would say drop that 14% down to at least 10%. I'd say you can likely go lower than that even.
If you've got a Dec - Most of July history, you likely can get a pretty good estimation of your bills for the other part of the year. Your big changes are likely to be heat and air needs, and you can take a look at what you've used in winter months and summer months, and typical climate values for the other months (and find comparable months that you've already got numbers from) and get a decent ballpark estimate. May want to look to see what the baseline electricity is (i.e. everything off, fridge unplugged and see what the draw rate is on the house) as this is 24/7/365 consumption. There's likely some things you can reduce there, and by doing so reduce the overall PV Size needs.
As for the Net Metering - the devil's in the details and little things can add up quickly. I'd make sure you fully understand them before ever pulling the trigger. That said, it sounds in general to be somewhat standard (if there is such a thing) net metering practice of a kWh in a kWh out, you get to carry over excess credit to the next month (check to see if there's charges on this - I effectively get credited about $0.028 less than the pay rate for any excess credit at the end of the month), and then at the end of the year, if the balance is positive (negative is a credit) you owe the balance, if it's negative, you typically don't get the full credit amount that you would have added up, but you typically get paid at distribution rates, which for me would be about $0.03/kWh (meanwhile my rates on TOU vary from $0.21-$0.23 in the 'Winter - Oct 1 - April 30' and $0.27-$0.37 - 'May 1 - Sept 30' That is to say, it's not a financial incentive to overproduce on an Annual scale, it doesn't hurt too much (that cost of having installed a larger system) but it also doesn't really help too much either.
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So many quick and helpful replies, thank you!
I do have 320A service, but I can see why no one would sell an inverter for that since most are 200A max.
Yes by single phase I meant 240v as you described.
I amable to feed back to the grid any power I do not use, then choose my retail provider on how that is handled. Should be able to find one where I can pull the energy back in kw for kw. Pretty sweet deal, batter bank I do not have to maintain! I did not see any regulation on how much I could feed back in, just that I would lose any extra after a year.
I do not have a good baseline for power as we moved here in December. Last month we were cooling half the house and used over 1500kwh.
According to pvwatts with a 14% loss rate I get about 21k kWh a year. Right now I think it will be about right for our 4600sqft house. I do have plans for being more efficient in the future however so it could be overkill in the future.Leave a comment:
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How much is a 14 kW array likely to generate per year in your area ? What's your annual usage ?Leave a comment:
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There are larger inverters for residential as noted SolarEdge has an 11.4kw inverter.
You will need to do a lineside tap or derated your MSP.
14kW for a residential install is pretty larger. Is your MSP 200A or more?
What is your annual average usage? You will want to check with your power company on net metering regulations.
Often there are limits to how much you can install in different regions as well as hard limits, there are often limits to a small percentage of overproduction (often 110% of annual usage).Leave a comment:
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Yes, the inverters tend to top out around 7.6kW. There's a good reason for this. Most residential main panels in the US tend to be at most 200A (most new builds will be 200A and most upgrades go to 200A service and panel.) And they have a 200A main breaker by default. And the 200A panel bus rating is 1.20% of that 200A (i.e. it's 240A), leaving only 40A more that could be fed into it safely (you can mix and match to provide 240A total from grid + solar if you wanted - so you could go a 180A main and 60A for the solar (if you can find a 180A main breaker.) But for code, they're going to limit you to 1.20% of feed, even if you know darn well you'll never pull more than 10-15kW at any giving time. They don't care if you're never going to meet those numbers, they want to make sure that if something does happen and you're driving both ends to the max you're not going to overheat the bus bar.
So why is 7.6kW the magic number? Well at 240V -> 32A, you size your breakers at 125% of the max current -> 40A breaker.
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You can also do two smaller (e.g. 7600W) inverters as well. I'll defer to others as to which may be the better approach.Leave a comment:
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When you say "single phase" do you mean normal USA 240V split phase? Aka two 120V legs 180 degrees out of phase?
Solar Edge has a 11.4kVA 240V inverter (I have one). You can put up to 15,350W DC (STC) on it in theory. Of course I wouldn't necessarily do that unless you have a fair amount of shade, difference orientations, etc. our else you're liable to get a fair amount of clipping.
What service is your main panel? 200amps or larger? You'll need to do a line side tap.
-Jonathan
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You can't use apostrophes' when a new poster, odd but look at where you were cut off.Leave a comment:
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High capacity grid tie single phase inverter
I found a supply of panels that were excess from a solar power plant. I want to do somewhere in the 14kw range for our house. However I noticed single phase inverters seem to top out around 8kw. Anyone know why? Should I plan to use two inverters?
Thank you littleharbor, could NOT for the life of me figure out why I was being truncated.
Side note: I could not resist buying more panels that I need, so If you are in the ft worth tx area and want some 310-325w Jinko panels for $145 let me know.
Last edited by Fourthbean; 07-10-2018, 03:42 PM.
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