That’s in a residential/urban context. I would assume (but have no actual idea, just common sense) that weight matters at least somewhat significantly in an industrial/grid scale context, where shipping and labor are for MW scale systems rather than kW scale systems. I’m not sure how important the weight is here, but it seems reasonable to think that it might be more significant than in a residential/urban context. Could also mean less land use, less structural steel, less maintenance for a system of the same capacity, etc.

It isn’t. A 500 watt panel is about 71 lbs, for 27.5 square feet. That’s the typical commercial panel. A little smaller than a normal 4x8 sheet of plywood.

Any structure designed to withstand 100 mph winds (typical in mild areas with no hurricanes or strong gusts) needs to be able to handle 25.6 psf - or 704 lbs - per panel just from wind load. Roughly 10x the panels weight.

In most of the US, add on snow loads from 20-100psf or more. I’ve installed panels in areas with 150psf design snow loads.

In the 150psf snow load area, that meant an additional 4125 lbs for that same 500 watt panel, each. Or about 58 times the weight of the panel. Steep angles (30 degree or more) can allow reducing that, which is a good idea.

So for instance in that area if not mounted very steeply, the racking needs to be able to support 71 lbs (panel) + 704 lbs (wind) + 4125 lbs (snow) per panel. Or 2.5 tons, give or take, for each 71 lb panel.

The panel is about 1.5% of the weight in that scenario.

And that is with no safety factor.

Now the roof has already been designed to bear these loads of course - but not as point loads randomly through the roof deck. So whatever anchoring/racking needs to transmit the forces effectively into the roof in a way it can handle without letting water through, and hopefully without making it impossible to maintain the roof either. And if in an area that freezes, without giving areas for ice to form and jack the roof/panels apart.

That isn’t trivial.

Great response, thanks for taking the time to write out the numbers!

What do you think about the implications for transportation, maintenance and land use? I have zero idea what the balance of those costs would be for a grid-scale solar farm, but ostensibly going from let’s say 20% to 21% efficiency means you need 5% less land, weight to transport from factory to site, fewer panels to inspect/build/install, fewer to purchase, etc.

I’m sure someone else has a better idea how much it would affect the LCOE than I do!

It isn’t going to make something economic that previously wasn’t. If the costs are sufficiently low (unlikely) it might have positive ROI in some scenarios.

Generally though, solar projects are go/no-go due to things like cost of money and electrical sales pricing agreements + site specific variables like insolation, flatness/road access, cost of local labor, local weather impacts on racking costs, access to transmission, and bulk wholesale costs of materials.

It’s hard to beat flat land out in the open desert near major urban areas with nearby highways and transmission lines, for instance.

What you’re talking about is likely at most half a percent of that equation.

Yep, that’s what I figured! And hence my original post at the top of this thread, suggesting that it’s easy to feel like we have sort of “solved” solar from a panel efficiency perspective and it’s everything else that we still need to improve on (grid infra, storage, etc etc), and additional percentage points of efficiency won’t really mitigate the existing limiting factors.

>That isn’t trivial.

Thank you. So often when discussing solar (or EVs) we see bizarre extrapolations of potential install rates that don't account for the fact that huge swaths of the country (the majority of places here in Canada) have real challenges with installation. These are not insurmountable, by any means. But those challenges are reflected in overall cost, making some of economics less favourable.

It’s always easy if we don’t know/talk about the hard parts!

In my experience, the panels themselves are at most 1/4 of the cost of any given system, even when discounting labor and permitting costs.

What proportion of the costs are down to permitting?

From 50% (or more) to 5% (or less) depending on local jurisdiction and scale.

If they want it to happen and aren’t greedy? It’s rarely a major problem. Otherwise, sky is the limit.

I know of a couple sizable projects that finally got cancelled because the local AHJ (authority having jurisdiction) finally just got too greedy. In one case they threw on an extra couple hundred grand worth of city park improvements as a requirement on a couple million dollar (small) project. Developer ended up walking away, as that was the fourth time they did that.

Some folks just can’t help but make it lose/lose.

So it sounds like large scale deployments have a larger proportion of the cost be due to permitting, and smaller scale (like on a house), would be fairly low by comparison.

Not really. It depends on how hard you can be squeezed, and how much they want to squeeze you.

Most large scale installations (if they’re smart) will be in areas where the planning authorities don’t have a lot of leverage.

Most residential installations (if they’re smart) will be in areas where it’s politically untenable to squeeze homeowners for outrageous fees.

Then you have the other places.

Either way, even large fees for a larger installation will be a small percentage of the total. $2000 worth of fees for a homeowner will be outrageous percentage wise.

For my residential 6.6kW ground mount array, less than 0.9%