Extreme efficiencies in STC W per square cm (or meter) are primarily of interest to things where room to mount PV cells is extremely constrained. Such as on satellites. Look at triple junction GaAs based cells used in satellite applications for example.
There are a large number of research-lab-only PV cells made in the last 10-12 years which greatly exceed 23% but are economically unfeasible or impossible to purchase for ordinary use. Some of this tech does trickle down eventually, however.
Of more practical real world interest is $ per STC watt for a panel you can buy in a 20-panel pallet load from an ordinary PV wholesaler. Like a figure of $0.28 USD/W for nominally 380W rated 72-cell monocrystalline Si panels for rooftop or ground mount applications. Meaning that a pallet of 20 panels would be somewhere around $2100 to $2200 USD to purchase plus freight.
In approximately the last 12 years we've seen things go from if you buy a pallet of "cheap" mass market 72-cell panels, you'd get 320W rated per panel (STC rating of about 4.44W per cell), to now being able to buy something that is 380W rated as mentioned above, approximately 5.27W per cell. All under STC measurement conditions which are only a rough approximation of real world sunlight of course. The same panels typically measure 1.99 x 0.99 meters so you can do the math on the improvement in STC W per square meter if mounting space is a limiting factor.
The cost of the panels is already such a small fraction of residential install cost. My panels were definitely under a buck a watt (maybe 15% of the total cost). The installation cost (i.e. paying for a team of a dozen guys to dangle in harnesses on my steep roof for three days) absolutely dominated the invoice (50-60%). The second most expensive was the batteries (about 20%). The remainder went into the hundreds of other parts (inverter, cut-off, conduit, circuit breakers, cables, MPPTs, brackets, safety stickers…) needed for a functioning & legal system. And a couple hundred bucks of fees to the city for permitting and inspection, and a couple hundred bucks for the off-shore engineers to draw the system design docs.
I won't make a profit for decades, unless the price of grid power shoots up. It would make more sense in a place with higher power costs. But I can keep the lights on if there's a power outage, without the maintenance costs (and noise) of a hydrocarbon-fueled generator.
If you're installing solar for monetary gain, don't put it on your roof, buy/lease cheap land and build a solar farm. My electricity provider even lets you buy in on syndicated solar farm deals, if you don't want to manage the process yourself; you get the generated kWh credited back on your power bill!
There was a story last week about commercial solar farms having panel flat on the ground and some people posted about putting home solar setups flat (or slightly elevated with a brick and tied down).
Saving money with the setup beats getting the last percent out of the install. Although probably only some rural home-owners are going to be able/allowed to just put the panels flat on the ground.
Haha, love it. Sure, you're losing a few percentage points of efficiency, but not THAT much, as long as you're within a couple dozen degrees latitude of the equator (COS(X) ≈ X for small values of X). And if you're far from the equator, why are you messing with solar anyway??
For a residential install (10s of square meters, not thousands). I would still feel more comfortable laying down some concrete first to minimize the chance of spoilage from vegetation. Plus something cheap for elevation from any flooding (bricks, cinder blocks, etc).
Yep, as soon as you start talking about flat panels on the ground, you start introducing problems with moisture, and/or snow/ice buildup in the winter.
Might be ok in some areas, but not at northern latitudes, and definitely not their winters.
I'd gotten a couple quotes for grid-tied solar installations recently.. and they were pretty outrageous @ over $5/watt installed (with no battery backup & no option to stay on with the grid out).
So now I'm in the process of putting together a 1.8kW solar system for the roof of a cargo trailer. Not the biggest solar setup, but I'm also not a huge consumer of power - this should offset a significant portion of my consumption in summer, and it's also expandable to ~2.7kWh (though I should've bought a 6th panel for that).
I've paired the panels up with a 3kW hybrid inverter and a 5.1kWh LFE rackmount battery. Should do pretty well together, and like you said... I'll be able to keep the lights (+fridge/furnace) on if there's a power outage - a huge plus.
Total cost for the main components and most of the necessary wire/hardware? ~$4000, before any tax credit.
Not just that, the other trend is that panels used for solar farms have massively increased in size & capacity. The panels we are now buying for our solar farms are 660W, and over 2 meters long. While not as feasible for roof mount (although we're speccing 575W panels for commercial rooftops), these large panels reduce our associated balance of system costs on a $/W basis.
Keep an eye on the panel construction though, the gold standard is glass-glass but there are plenty of other materials used for the sandwich (and the sealing!) and not all of them will stand the test of time.
This is also relevant to large-scale installations. For a single family home, perhaps you don't care if you use 30% of the roof area or 32.5%; but if you're building a solar farm for a whole city, then those extra 2.5% are a good number of Km^2 which you can save; or have as extra safety-margin production capacity.
There are a large number of research-lab-only PV cells made in the last 10-12 years which greatly exceed 23% but are economically unfeasible or impossible to purchase for ordinary use. Some of this tech does trickle down eventually, however.
Of more practical real world interest is $ per STC watt for a panel you can buy in a 20-panel pallet load from an ordinary PV wholesaler. Like a figure of $0.28 USD/W for nominally 380W rated 72-cell monocrystalline Si panels for rooftop or ground mount applications. Meaning that a pallet of 20 panels would be somewhere around $2100 to $2200 USD to purchase plus freight.
In approximately the last 12 years we've seen things go from if you buy a pallet of "cheap" mass market 72-cell panels, you'd get 320W rated per panel (STC rating of about 4.44W per cell), to now being able to buy something that is 380W rated as mentioned above, approximately 5.27W per cell. All under STC measurement conditions which are only a rough approximation of real world sunlight of course. The same panels typically measure 1.99 x 0.99 meters so you can do the math on the improvement in STC W per square meter if mounting space is a limiting factor.
https://footprinthero.com/standard-test-conditions