To figure out what card you should be using to mine with “free” electricity we have to identify what is meant by free electricity and whether or not there is a limit to it.
If you’re mining on a solar system that you paid for then you have a limit on how much electricity you can use consistently throughout the day. When we are limited in how much power we can use, we have to look toward efficiency rather than speed to utilize the amount of free electricity we have available in the best way possible.
This is normally measured in kw/hash or basically electricity to hashrate ratio. How much hashrate can you get per 1 kilowatt of electricity (efficiency).
Other things that can limit your “free” electricity would be if you you’re getting electricity included in rent where if you start running up $500 electric bills on your landlords they’re going to start to wonder what you’re doing and raise your rent.
So be very clear and careful what you mean by “free”.
Just because you don’t pay for it doesn’t mean someone else isn’t and just because you spent a god awful amount of money on a solar system doesn’t mean you didn’t pay for electricity up front. It’s never really free unless you’re stealing it.
In situations where you’re trying to either hide your usage or utilize the limited quantity you have we will always look for efficiency. The most commonly used card with a high efficiency rating in kilowatts per hashrate is the NVIDA RTX 3070. Although this will vary across all the algorithms the 3070 is a very safe card to have to mine for efficiency.
On the other hand, if your electricity is truly free and unlimited then you would want to minimize the amount of cards you have while maximizing your total hashrate.
If money isn’t a concern then you would just load up on 3090ti’s or try to get a hold of the new 4090. You will always use the most powerful card when electricity is truly free and unlimited. They aren’t the most efficient but you will get the best speeds out of them with the least amount of cards possible.
If you’re looking for the best bang for your buck then the formula to determine what card you should be using if electricity free is to use the dollars per hash rate formula. For example, if an RTX 3070 can safely get around 60mhs on Ethash and they are selling for $400 then the ratio becomes about $6.66 per megahash.
This is the formula we use to determine what the best deal is when we don’t care about how much electricity costs.
Now you may notice that the best card to use is actually almost entirely dependent on what price you get the card at. This allows us to look for deals because the best card isn’t a specific card, it’s the card that you can pay the least amount of dollars per hash for.
Take for example that same 3070 @ 60mhs @ $400 for $6.66 per mhs.
Say we find a 1660 super that runs at 31mhs for $150. Well when we do the math for that 1660 super we get a total of only $4.83 per mhs. This means the 1660 super in this scenario is actually the better card in terms of cost per hash rate.
Thus, the cards you will buy when electricity doesn’t matter at all will rely on what price you’re getting the cards at. There won’t be a single card to get in this scenario, because the card you should get will always be the cheapest one you can find per hashrate.
So to sum it up.
When electricity matters, get an RTX 3070, when it doesn’t get the fastest card possible that has the cheapest cost per hash.
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