Cost summary of running a cryptocurrency mining rig off-grid

Cryptocurrency is all the rage and when thoughts turn to mining it, the conundrum, for Australians at least, is the cost of electricity required to power any sort of crypto mining setup. Once you get on to that train of thought, the mind turns to solar power. Free energy from the sky! But how much would a small off-grid solar power setup large enough to power a mining rig cost to set up? That’s what I’m going to try and bumble my way through in this post.

Please don’t use this info to hook up your fancy mining rig to some solar panels. I’m not an electrician and I don’t know how it all works exactly. I don’t know how the MPPT controllers hook up to the solar panel strings and then to all the batteries. I don’t know how to install voltage cut-off devices so you don’t ruin your batteries. The only point of this post is to get a rough idea on the payback time for mining with solar panels instead of grid power – not an instruction guide to run your rig off-grid.

A rig with 6x AMD RX580 GPUs uses around 1200W. It’ll use that 1200W all day and all night. This website is a handy calculator for sizing off-grid solar setups (mainly for people in caravans – imagine we’re in a crypto mining caravan ok). Plug some numbers in – 5A (1200W/240V) for 24hrs a day and the result for a Melbourne winter scenario (i.e: bugger all sun) is 2337W of panels and a 533Ah battery setup.

To make everything simple, I’m going to keep the system at 12V and use a 12V pure sine wave inverter to get my 1200W @ 240V. I liked the look of this one on eBay for $160. It’s one of the cheapest I could find and I have no idea if it’s any good. Could be a fire hazard, or could be a bargain. Luckily this is all theoretical.

On the other end of the system are solar panels. I need 2337W of them. I thought that 10x 250W panels will do the trick, but as I’ll explain later, I think I need to split these up into 3 sections to run 3 “strings” for each MPPT charge controller, so 15x 200W seems like a better idea than 10x 250W panels. This joint is selling them for $139ea. 15 of em is $2,085.

The  calculator also told me I need a solar charge controller that can handle 176A of of electricity. There’s no charge controllers this beefy that I can see in my limited research, so I’ll need more than one and set up a few “strings” (I don’t really know what that entails, but I think that’s the way to go). 60A MPPTs seem to be bang for buck @ $200ea, I’d need three of them to handle 176A. Like the inverter, I also think these are a fire risk.

In the middle of all this, I need some batteries. A whopping 533Ah of them. From looking around eBay, it seems like Australian made Century deep cycle flooded batteries don’t cost much more than the cheapo Chinese ones, so I’m going to get 6x N70T units, wire em up in parallel. They cost $238.99ea at Supercheap Auto. $1,433.94 all up.

To summarise:

  • The sun hits 3000W (15x 200W) of solar panels
  • That energy is taken to 2x 60A MPPT charge controllers
  • Which are hooked up to 6x Century N70T batteries
  • That the 12V pure sine wave inverter connects to via a voltage cut off thingy
  • The mining rig plugs directly in to the inverter

Costs:

  • 3000W of solar panels (15x 200W) – $1690
  • 1500W pure sine wave inverter – $160
  • 3x 60A MPPT charge controllers – $600
  • 6x Century N70T batteries – $1443.94
  • sundries (wiring, panel mounting hardware, etc.) – $500
  • TOTAL: $4,393.94

So let’s round it up to $4500 for stuff I didn’t think of. That’s $4500 to power a 1200W computer off-grid, all day and all night. How long would it take to recoup those costs versus just plugging the rig in at home in the garage?

Assuming you pay 20c/kWh for energy (that’s about what I pay down in Victoria), you’re looking at $5.76 a day to run the 1200W rig. It would take 782 days, over 2 years to recoup that investment. So only after 2.1 years is your power “free”. If you plan to mine for the long haul, I guess it’s alright.

Now if you didn’t have anywhere to plug a rig in (say, a shack in the bush, where there’s no grid) and you decided to get hooked up to the grid specifically to mine crypto, you need to take into consideration the daily supply charge. That’s $1.045/day for me. Add that in, the rig costs $6.805 a day to run – 661 days until break even. 1.8 years.

I don’t know what to do with this information, but I’m glad I spent half the morning figuring it out. I am 100% sure I’ve made mistakes in here, so if you read it and want to educate me, sling an email to anthony@thesizzle.com.au

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