Choosing high power panels

[Orangesauce]

Hi I am trying to finish specifying my system and need to learn how to choose panels.

I'm using NREL SAM to configure the system, but choosing a panel so far in my journey has been more about looking at a couple of online vendors and searching by popularity for configuration prototyping. Now that I am ready to buy, I need to figure out how to do this empirically.

My goals for the panels:

• These are going on a roof and real estate is a valuable factor that is not captured in $/W. Ideal panels are high wattage
• The geography is metro Denver, high altitude, hail and wind are factors
• The roof is tan tile, don't think they have enough albedo to justify bifacial
• Considering lifespan target at 10 years since I'll probably rotate by then

I've downloaded the CEC database and can filter it, but is it the best source of information? It doesn't appear to have changed since 2021-Oct.

Thanks!

 

[Hedges]

Depends what you want to achieve/optimize.

Consider size and weight, especially if this is DIY install.

A bunch of us have bought from Santan solar (they have mostly used, some new leftovers) and Inxeption.
We're now looking at prices between $0.17 and $0.25 per watt.

You'll have a hard time getting panels that only last 10 years, except old degraded ones or no-name brands. But there are differences, accelerated life tests show various degradation mechanisms and some panels score much higher than others.

Design your system with SCC or inverter MPPT specs and PV panel specs. Some aren't a good match.

 

[chrisski]

Accurate measurements of the roof including where vents are is important. There is also Walkways along the edges you can't build up to and this is different by your jurisdiction.

These are going on a roof and real estate is a valuable factor that is not captured in $/W. Ideal panels are high wattage

This makes me think you have a small roof that you are trying to fit the most wattage on. Once you have the measurements, vent placement, and the places you can't put the panels, now you can figure out the area you have to work with.

You may be looking for a higher efficiency panel to get more watts / m2, but in my limited experience, when I did the puzzle together where I filled the roof on my RV, higher efficiency panels were not as important as one that fit the area.

 

[Orangesauce]

A bunch of us have bought from Santan solar (they have mostly used, some new leftovers) and Inxeption.
We're now looking at prices between $0.17 and $0.25 per watt.

Wow, I did not know about these suppliers. Those are really great prices, thanks!

So are folks mostly just shopping for $/W and (as @chrisski notes) by size, then using the electrical parameters to configure strings?

This makes me think you have a small roof that you are trying to fit the most wattage on. Once you have the measurements, vent placement, and the places you can't put the panels, now you can figure out the area you have to work with.

It's a five-sided trapezoid in the 750 sq foot size range before subtracting for standoffs. I need to ask AHJ what standoffs are acceptable and whether adjoining roof geometries with less ideal planar orientation are acceptable for walkways. But your point is well-made that different panels will have certain advantages for specific roofs and it's worth knowing those measurements very precisely to start.

 

[chrisski]

I don’t see any room for vents in the white panel layout.

The contractor that installed mine had a software for pAbel placement, and for final plans required someone coming out to make measurements.

 

[Orangesauce]

I don’t see any room for vents in the white panel layout.

There are none

 

[Hedges]

There is a requirement of either 36" both sides of ridge or 18" both sides, some rules around valleys, and walkways. These are for fireman access and hacking vent holes. The rules vary by state, sometimes eaves count for walkway and sometimes that must be within walls.

If high wind area, may want to keep panels back from the edge for less uplift.

Most important to me is keeping water out of house, rather than quick installation. I'm planning on flashed standoffs.

Design your system and get it and the layout reviewed to avoid do-overs.

I see you're on some other threads. Figure out what you want the system to do, like backup and time shifting. Once you buy something, options for adding other features are constrained. Net metering? Does the system make financial sense at all, or is your utility rate cheaper than PV?

 

[Orangesauce]

I see you're on some other threads. Figure out what you want the system to do, like backup and time shifting. Once you buy something, options for adding other features are constrained. Net metering? Does the system make financial sense at all, or is your utility rate cheaper than PV?

Most of my threads are from three years ago and I've learned a ton since then. I want some small amount of battery and have extracted an ideal (for me) protected loads panel that originates in a new panel next to where the inverter will go (probably a 12k Sol-Ark or EG4). It's Colorado, so I need heated batteries, and that's pushing me toward the Sol-Ark and Pytes batteries. EG4 seems to have a nicer rack and busbar arrangement though. SAM simulates the best use of this all and I'm very confident about the load profile and production at this point. Payback on the full system with my imported local rates, a single 10kWh battery is at 7.3 nominal and 12.5 years discounted.

 

[Hedges]

Battery costs extra, pushes break-even out. 7 years is somewhat attractive, 12 years less so, if just in it for the money, so depends on what else you might do with your cash.

Have you figured out what the numbers would be for grid-tie PV with string inverter?
If the hybrids you're considering are batteries optional, also compare those to tier-1 string inverters, where we have a couple decades track record.

SolArk is a newcomer but people are happy so far. EG4, well, I'm sure you're read about it here. With payback in the 10+ year range, be prepared for possible replacement costs during that time.

I had 5x SMA SWR2500U running for 17 years, two failures, calculate about 32 or 34 year MTBF.

Lithium battery maybe can pay for itself if time shifting is worthwhile. I think claimed cycle life should reach 16 years deep cycling.

Lithium and AGM are about same up front cost these days, which almost makes it a no-brainer, but AGM is simple and has some advantages, worth considering for a backup system that only cycles during power failures. The tables have pretty much turned already, but we do read of issues people have with BMS.

The EG4 PowerPro looks interesting, being weatherproofed and larger cells. Some people are experiencing hiccups integrated with some inverters, I think. Glad I'm still on the sidelines, and picked up some used AGM for $0.15 on the dollar, will carry me through until the lithium products mature and shake out the market.

 

[Orangesauce]

Battery costs extra, pushes break-even out. 7 years is somewhat attractive, 12 years less so, if just in it for the money, so depends on what else you might do with your cash.

Have you figured out what the numbers would be for grid-tie PV with string inverter?

Yes, without the battery and just a GoodWe grid tie inverter, 4.3 years. All systems including $5,500 in costs for racking, installation, engineering and permitting (it's a metro area). If I can get that down, all the better. Note that 4.3y is just the amount of time to recover the numerical amount of dollars that were originally invested, but those dollars were worth more.

When I say "discounted", I mean including the effects of inflation and the present value of the money. A faster ROI means there's less time for the cost of the money to drop, that's 5.8 years with a grid tied string inverter and no batteries.

The cost delta above this for the Sol-Ark 12k and a 10kWh battery is $5K. There is some value in summer time-shifting, but not enough to pay that off with one battery. Out of curiosity from your questions, I will run some simulations with a larger bank of batteries and see if there's any benefit. Mostly it's just keeping the basics going in blackouts – heat, refrigeration, internet, a few lights. The HVAC is getting upgraded to a dual fuel system that will work even when the condenser is unpowered.

FWIW, I found a pallet of used panels on Santan tonight and bought them, thank you! $0.21/w was good enough not to lose as the weather warms up. So I guess I answered the questions I started this thread with lol...

 

[NC_hydro]

Most of my threads are from three years ago and I've learned a ton since then. I want some small amount of battery and have extracted an ideal (for me) protected loads panel that originates in a new panel next to where the inverter will go (probably a 12k Sol-Ark or EG4). It's Colorado, so I need heated batteries, and that's pushing me toward the Sol-Ark and Pytes batteries. EG4 seems to have a nicer rack and busbar arrangement though. SAM simulates the best use of this all and I'm very confident about the load profile and production at this point. Payback on the full system with my imported local rates, a single 10kWh battery is at 7.3 nominal and 12.5 years discounted.

Check out Trophy Batteries for heated batteries.