Solar production. Panel ratings/claim vs reality

[ning]

Max 24 - yes this is what I recall now 10 years later .25% per year - I thought it was 2% but as mentioned in 10 years we have not seen any appreciable drop of generation with the LG 300 Mono panels. These panels were the best you could buy in 2014 and also you are correct if you buy a lower cost panel with a .4 or ,5% per year, just add 2 or 3 more panels.

I wish I had installed 10KW instead of 7.2 KW ($32K vs 26K at the time) as I got a quote in 2020 to increase to 10KW - a new inverter, and 6 panels was $15K - a no go - and if we installed 10KW initially it would have cost $6K more. Hindsight is 20-20, shoulda bought once and been done with it.

The upgrade path is IMO the best reason to go ground-mount, assuming you have room to add additional mounts.

I have a neighbor who looked into upgrading her solar capacity; everything's on the house (roof) right now and there's no room for more panels - so "upgrade" means "replace", and that probably goes for the inverter too. I suppose if you're near the end of life on the panels that's ok, but otherwise it's like saying instead of the 200hp engine in your car you want 300hp and that requiring a new engine completely (instead of a big phat muffler, trust me that's all it needs).

I set up my system so I can "upgrade" it by adding another mount with more panels & inverters and feed that into the existing combiner box (which already has room for the connection); the only "upgrade"="replace" part of it would be swapping a heftier breaker at the service end of the big power cable from the ground mounts (the cable was spec'd for future upgrade at a relatively minimal price increase that was far less than running more/replaced cable).

 

[LD1]

OP I think you should try to lower your 2200kw a month useage before you go solar.

I agree with reduction of usage as well - insulation, more efficient heat/air conditioning etc.

Cant really do that. Honestly, I dont understand why people make these statements.....

I use what I use. No more and no less. Are there people who use less kwh than me...sure. Are there people that use more....sure. But what do I cut? Lay in bed at night and not watch TV? Dont cook as much? Rush through a shower instead of enjoy it for 8-10min? Tell my wife and kids they cannot take baths? 2200kwh in the middle of winter in north-central ohio is not bad for an all electric home with 4 people and a full basement.

And whether or not I could reduce winter usage...to even say that of summer down around 1600-1800kwh.....how would that change anything with wanting solar? It wouldnt change the size I want to get....it wouldnt change my payback ROI, and I'd still fall pretty short in winter.

 

[ponytug]

@LD1 I hear you. While insulation and a more air tight home are probably desirable long term ideals for reducing energy usage, sometimes the cost / benefit analysis comes out on the side of just installing more solar.

That said, heat pump water heaters and dryers have come a long way.

All the best,

Peter

 

[ericm979]

A while back we got an energy audit done on our house which told us what was cost effective to address. They did a blower door test for leaks and used an IR camera to find where the insulation was lacking. It was worth the cost.

We're definitely going with a heat pump water heater in the new house. I'm on the fence about the heat pump clothes dryer- from what I read they're not as much more efficient as the heat pump water heater is, and have some reliability problems.

 

[LD1]

While I dont have a heat pump water heater.....I have a pretty efficient setup with a buffer tank and the desuperheater on the geo thermal. My buffer tank usually runs somewhere between 90-110 degrees.

So when I actually do consume hot water.....my regular water heater dont have to go from tap-cold to 130. It only has to go from ~100 to 130

 

[NorTracNY]

Sorry, but I only read the first 15-20post. My system was sized by a distributor of SunPower. They slightly oversized it and it has produced more than I use about 30% of the time. Call your energy company, but I'd be shocked if they true up each month. It's yearly for me and I've never heard otherwise. Keep in mind that the panels will produce less over time. SunPower says 0.5% loss each year. I went with leasing with SunPower, so they guarantee production and send me a check the years the panels don't produce the minimum.

 

[ponytug]

Sorry, but I only read the first 15-20post. My system was sized by a distributor of SunPower. They slightly oversized it and it has produced more than I use about 30% of the time. Call your energy company, but I'd be shocked if they true up each month. It's yearly for me and I've never heard otherwise. Keep in mind that the panels will produce less over time. SunPower says 0.5% loss each year. I went with leasing with SunPower, so they guarantee production and send me a check the years the panels don't produce the minimum.

Many, and an increasing number of utilities true up each month. Older tariffs were generally set up around an annual true up, but utilities realized that annual accounting gave them a more expensive cost/kWh and are being phased out.

E.g. In California, the original net energy metering (NEM) tariff was done on an annual kWh accounting basis, with no regard to generation time of year, or time of day that the electricity was used or generated. NEM2 required time of day accounting on a time of use tariff (TOU) that accounts annually for all usage and generation by the time of day, off peak, mid-peak, and peak rates. The current NEM only credits at the underlying generation cost ($0.02/kWh)and charges the solar customer for the transmission and maintenance costs (that can be $0.3-0.5/kwh), so a customer would need to be an enormous annual net generator to net their bill to zero (and that much overproduction is disallowed by the utility). Locales that follow the national building codes generally require an electrical meter and connection for occupancy.

As far as I can tell, nationally most utilities are heading towards a NEM3 type of tariff as this aligns better with the actual costs of production.

Pricing transmission, administration, and maintenance costs is really a monthly meter fee, but most places aren't there yet. It is rather like looking ahead to what replaces a fuel tax if a significant fraction of vehicles aren't gasoline or diesel powered.

All the best,

Peter

 

[LD1]

Sorry, but I only read the first 15-20post. My system was sized by a distributor of SunPower. They slightly oversized it and it has produced more than I use about 30% of the time. Call your energy company, but I'd be shocked if they true up each month. It's yearly for me and I've never heard otherwise. Keep in mind that the panels will produce less over time. SunPower says 0.5% loss each year. I went with leasing with SunPower, so they guarantee production and send me a check the years the panels don't produce the minimum.

It would have benefited you to read beyond the first 15-20 posts.

Because monthly is EXACTLY how my power company does it.

But that's irrelevant. I was seeking information about system sizes....vs actual production. Which you provide neither. Only a recommendation to call my power company....which I have several times....because you dont believe the facts as they are. Thanks.

 

[NorTracNY]

It would have benefited you to read beyond the first 15-20 posts.

Because monthly is EXACTLY how my power company does it.

But that's irrelevant. I was seeking information about system sizes....vs actual production. Which you provide neither. Only a recommendation to call my power company....which I have several times....because you dont believe the facts as they are. Thanks.

If I didn't supply the information that was useful enough for you, the mature thing would have just ignored. The information that I supplied was regarding that for the system I had installed, they GAURENTEED a certain amount of production. Most years they failed to meet this production and that is with them knowing that they'd have to pay me if they didn't meet it. It also notes that production will decrease over time. I was attempting to be helpful so you understand this company over promised. I would expect a company that wasn't financially on the hook for a minimum amount to be off even more.

For anyone to give you their system size and actual production is not useful. Before sizing, the company has to come out and take measurements. Your latitude, angle on installation, and clearance all come into play. Sorry that you were unable to obtain that from what I wrote.

 

[LD1]

If I didn't supply the information that was useful enough for you, the mature thing would have just ignored. The information that I supplied was regarding that for the system I had installed, they GAURENTEED a certain amount of production. Most years they failed to meet this production and that is with them knowing that they'd have to pay me if they didn't meet it. It also notes that production will decrease over time. I was attempting to be helpful so you understand this company over promised. I would expect a company that wasn't financially on the hook for a minimum amount to be off even more.

For anyone to give you their system size and actual production is not useful. Before sizing, the company has to come out and take measurements. Your latitude, angle on installation, and clearance all come into play. Sorry that you were unable to obtain that from what I wrote.

I dont care that you leased or with that company. I am doing neither.

And yes....your system size, actual production, and location would be extremely helpful. Because that is real-world data and not a MFG's claim.

And simply put...that is the question that I have asked, and the purpose of this thread that you have replied to now TWICE, and given nothing at all useful.

If you dont want to post you location, system size, and production numbers.....then why post?