I have a madone that I’m thinking about converting to di2. First, is it worth the extra cost?

if so, about how much is it (excluding labor) and where is the best place to buy it?

It is going to be expensive. In addition to buying the group, you will need to buy all the cables and then pay someone to take out the old stuff and put in the new stuff. It is great stuff but unless you just can’t live without it, maybe wait until the next bike.

Trek buys a lot more groupsets than any individual, same for Giant and all the rest, so they get better pricing. Buying it as part of a bike is usually more cost effective than buying it standalone.

Di2 is really nice. Modern mech groups are really nice, too.

Like most people who've used it for a while, I'd prefer not to go back. But I wouldn't spend a grand to add it to a bike that already has good shifting. (I'd rather have 105 and a power meter than Dura Ace Di2 and no PM.)

You can get an upgrade kit for about $1000(ish). You can then sell the mechanical stuff and make a decent amount of the money back, so it usually turns out to be cheaper than simply purchasing the Di2 model (in my experiences, at least).
Merlin is by far the best place to shop for groupsets. It's also a pretty straight forward process, so as long as you can bleed brakes, you can do it yourself.

And yes, it's 100% worth it...it just works. Always.
My bike with GRX shifts very well, but needs frequent fiddling to keep it that way. While my di2 needs nothing.

He has a Madone. It won’t be simple.

No, it'll be simple. It won't be easy, but it'll be simple.

Biggest issue is removal and re-install of the bottom bracket, which is likely a press-fit, thus might need the services of an LBS. You need to do this in order to lay in the E-Tube cables and find a place for the B port. Chasing the cables isn't difficult after the b-bracket is out and I'm assuming the frame uses internal cabling for the mechanical system currently, thus should have the holes sized for the E-Tube connector. OR the frame has one of those nifty removable access hatches on the bottom of the b-bracket that allows easier access to the cables thru this area. My Specialized Chisel mt. bike has one of these. If doing all this yourself, you need the tools and skills to install a hydraulic brake system as well, such as connecting hoses and feeding fluid. If your h-bar and stem are setup, you can use the bar-end A junction.

I got my system from Texas Cyclesport as they package and price well. You do not need a new crank, might want to put in a new b-bracket while the old one is out, do not need the brakes or rotors, so need to price a system of;
- Di2 hydro shifters
- Di2 F & R derailers.
- Battery and a seat tube holder
- A junction
- B junction
- BT unit if you want to configure using BT or want a BT connection to a cycling computer
- 6 or 7 assorted E-Tube cables

Kit for above from Texas is $1169

It's a BB90 frame - the bearings press directly in. Most Treks also have an access hatch/small storage cavity under the DT bottle cage.

that’s where my battery is located.

Do you currently have any shifting problems? If not, then I'd wait and get it when you get your next bike. My 105 5800 I put on my old Paramount shifted flawlessly, immediately and quietly in all gears. Only needing trim in the big big combo.

I just got a new bike with Ultegra Di2 and I see that I will eventually get to where I wouldn't want another without it, but....... I wouldn't spend the extra money to upgrade. So far my 105 bike is quieter, shifting is the same. I only got the Di2 bike because it wasn't much more during the spring sale than the same model without.

I too would rather save the money for a power meter and some other things.

The OP never stated he had to choose between Di2 and a power meter.

No he didn't. In fact I thought those might have been PM pedals on the bike. I was just adding to the comments of others that felt that way. Sort of like a +1.

What help do you have for the OP?

The OP asked for opinions about whether Di2 is worth the expense, and a couple of us offered opinions of where it sits on the superbike needs hierarchy. If the OP already has a PM then the two posts you quoted are yeses.

They don't seem like yeses to me​ -- quite the opposite.

Well hopefully the OP understands. I have not a clue where you stand.

The OP ask if it was worth upgrading his current bike to Di2. So if I"m only allowed a yes or no, then for me it will be a no. But if they want to buy a new bike, then it would be a yes.

I guess I was weaving too complicated a thought in my first answer. <grin>

Speaking of GRX, are any stock bikes out yet, available with Di2 GRX?
Also, I like some of the Giant bikes (endurance, gravel), but they don't seem to offer Di2 for any model of bike they sell. Why not?

I didn't come across any when I was searching. In fact, I even had to convert my bike (Orbea Terra) to standard GRX myself, as it still isn't a commonly equipped groupset. I do wish I went with the Di2 though, since the price difference wasn't that great.

Then I know Giant offers the Defy with Ultegra Di2, but yes, none of them come with GRX Di2...but I'm guessing it will become more common in the next year or two.

It depends on how much you want it! R8070 is clearly better than R8000, but it comes with a price, especially if you already paid for a groupset and want to replace it.

I wanted to upgrade my previous bike with CF rims & Di2 and I ended up replacing it. After running the numbers, I realized that the upgrades would have have cost more. It was pointless (for me).

Di2 works really well. Though I was quite negative about charging batteries for my bicycle, I finally got tired of having to readjust the shifting every other week as there was a little wear here or there. Using the long arm Di2 rear derailleur you could shift a 34 tooth. That is the same gearing as a standard triple.

The only dangers with the battery is the damn things last so long that it is easy to forget to charge them. They shift perfectly reliability time after time.

That particular Madone is NOT a good target though. It was never designed to have internal wiring and although you CAN get the internal wiring to work, you would probably have to use an external battery. These are fine if you know that you have to have the EXACT external battery holder for the specific group. There are three or four and the entire system looks dead without the proper battery mount.

It also requires practice to use. That shouldn't be a surprise but it usually is. Just like you have to learn when you cross from Campy to Shimano to SRAM, you have to learn either Di2 or the SRAM wireless equivalent. The charger that plugs into your computer and charges an internal battery for your Di2 this will configure your system a number of different ways. I started using light long finger gloves and it was pretty difficult. Then it got warm for a couple of days and I could practice with short finger gloves and found what to expect. The other days I used heavy gloves and could easily shift.

To tell you the truth I can't see any more advantage of manual shifting anymore. Cables slip, the shifting cogs in the levers wear or get dust in them and stop shifting, the derailleurs have to be readjusted now and again. And the front derailleur in particular has to be micro-adjusted as you move across the cogset to keep from wearing it. Di2 self-corrects so all you are doing is shifting.

As others have said, in general it is best to buy a bike with the Di2 installed. It is a pain in the butt to buy the correct length wires (6 to 9 at $25/each) and getting them to work. Now perhaps Trek has a method for installing an internal battery but they don't for my 2012 6.9 and told me I would need to drill a hole in the frame and glue in a special wire entrance/exit in order to mount the external battery mount. That also means that you have to buy a separate Bluetooth interface. The latest internal batteries have Bluetooth built into them. And you need that to connect with your Garmin to show speed and cadence off of your back wheel instead of the front one thus screwing up the bike aerodynamics.

I suppose you bought that bike complete. But the disk brakes are a snap to bleed once you know how. I accomplished it in 30 minutes from scratch and it worked perfectly. I did an entire external wiring which is something of a problem since you have to be careful with the wires and get their length very close to perfect. Nothing would work until a shop guy printed out a chart off of the Trek manual site that showed the correct and NOT interchangeable external battery mount and then everything fired right off and worked instantly.

My judgement? I won't go back to manual shifting. As for Ultegra or Dura Ace? The Dura Ace levers weight nothing at all. But everything else is pretty much the same weight as Ultegra and I can't see any point in Dura Ace other than the levers.

As far as I can tell GRX is just the long arm rear derailleur. The rest of it is a about 05 quality parts or perhaps Ultegra with GRX markings.

I did mine on the cheap buying a used partial kit off ebay and doing it myself. My bike came with the 6800 series Ultegra so the 6870 kit I bought matched everything I already had. I had to get creative with the installation as my bottom bracket shell is a piece of aluminum tube molded into the frame so I couldn’t run the junction b out the bottom bracket to hook it up. Ended up running everything up the seat tube and stuffing it back down. Didn’t rattle the few times I’ve been out so I’ll call it a win.

I will say it’s not for the faint of heart as it requires a bunch of putzing around to get everything where you want it but in the end I’m so glad I did it. Assuming you Madone is internally routed you’ll likely have an easier time as I believe they use the same from for mechanical and di2, whereas mine was only offered in mechanical so the provisions for di2 weren’t there.

Thinking about it I'll bet you that Trek makes a special internal battery mount for that shape of seatpost. Believe me, they make everything else. Except for my 6.9.

It looks like Giant had a 2019 model Defy with Di2, but nothing in 2020 lineup.
https://www.giant-bicycles.com/us/bi...anced-pro-2020

Also, for Gravel, Giant highlights one of their pro riders on a Revolt with GRX Di2.. but it's not a sold edition according to the bikes pages anyway. Not even available in manual GRX for that matter
https://www.giant-bicycles.com/us/ne...advanced/24717

Since none of us know the OP's financial situation, a straight yes or no isn't a helpful answer. The best way to be helpful is to provide context. I'm sorry that seems to bother you, it shouldn't, but these are stressful times and everyone is a bit on edge.

Ah yes, you are correct. It was the 2019 model that I was thinking of. It does seem like more and more brands are going with Sram over Shimano on their electronic-shift models, these days...