What makes a good PI system

I came across some postings of you in the eve-online wormhole forums where you gave good advice to some people. You seem to have some expertise regarding PI in wormholes. I'd like to set up a pos in a wormhole system during the next week or two. Which class I will choose will be decided by other factors but I will definitely give PI a try. I just don't want to see myself setting up in a system that turns out to be bad for PI later on. Do you maybe a have an up to date link at hand that helps at rating a wormhole system regarind PI? Like a tier list of planets or which combinations are good. All I find is either very outdated or not giving advice on which planets/wh systems are good for PI. That would help me a lot.

This is from an Evemail I received recently, and it's a really good question. I've talked about the importance of a good PI system, but never really gone into detail on what a good PI system actually looks like. 

The quick answer

Look at a list of all the planets in your w-space system. Cross off all the gas planets, and all but the smallest of the barren planets. Cross off all the planets with a radius of more than 10,000 km. Do you still have five or more planets on the list? If so, you probably have a decent PI system.

Examples: 

Chaos has six planets. Three of those are gas planets. One of the remaining planets has a radius greater than 10,000 km. That means the system has only two truly productive planets, one of which is a barren planet.

Vanaheim has ten planets. Three of those are gas planets. One of the remaining planets has a radius greater than 10,000 km. There are two barren planets. That means the system has five useful planets.

The reason we put the cut-off at five planets is because that's the number of colonies you can support with your skills at IV. Having more useful planets gives you more options, but won't typically make you any more ISK. Having fewer planets than that means that some of your skills are going to waste, however.

The complete answer

The value of any PI system is ultimately what you can make in that system. That is a function of a) what resources the system has, and b) how easy it is to extract those resources, and c) the value of those resources, either on their own on in combination with each other.

What resources?

When looking at what resources a system has we generally disregard gas planets. Gas planets are the most common, and the abundance of those resources makes forces their value down. The exception would be if you need Reactive Gas for industrial work, as this can only be found on gas planets. If you are planning on simply hauling to market, I'd give it a miss.

Barren planets are nearly as common as gas planets, and they don't even have a unique resource. However, they are useful as factory planets (the highest tier factories can only be built of barren or temperate planets, and you would never waste a temperate planet by putting a factory on it), so one is okay.

The remaining planets are your bread and butter, with bonus points for temperate and lava planets, which each produce a unique resource.

How easy to extract?

The various planet types set the spectrum of resources available, but actually getting those resources is a function of density and planet size.

Planet size restricts extraction by increasing the cost of your links (the connections between each of your facilities). The more power grid you spend on links, the less you have to spend on extractor heads. Resource density determines how many extractor heads you will need to keep your factories fully supplied.

So, a planet with a desirable resource may fall short through a combination of being too big, or the resources being to diffuse. Equally, a planet that you might otherwise write off may be workable because of very high densities or extremely small planet size.

For example, I have one lava planet in Vanaheim. It has a decent planet size. Unfortunately, it has almost no Fensic Magma, the resource unique to lava planets. Instead, I have to harvest something else. This turned what could have been an amazing planet into a mediocre planet.

Conversely, I have a storm planet with a radius of 16,000 km. However, the resources are so dense that I am able to efficiently produce Coolant there, despite the planet size.

What is the value?

Once you have worked out what you could extract, you need to work out what you should extract, and possibly produce.

Websites like this or this can help you work through the possibilities, and once you've worked out what is possible, you need to actually check the markets.

When I worked through all this in Vanaheim, I found that any P2 product with a Jita buy order of more than 16k ISK per unit was 'good', while 17k or higher was 'amazing'. 14k ISK per unit was mediocre, and anything less than that was just bad.

For P3 production, 105k ISK per unit is a good target, and more is possible.