There is an incredible amount of misinformation about power groups that continues to circulate the IsR Steam forums and assorted Discords, and I've often found myself repeating the same information over and over again. I've put together this guide as an easy way for me to combat this misinformation. As my knowledge base of IsR is often called into question in these misinformation posts, here are some "credentials" for you. I've been playing IsR for over two years now, and have spent the last year and a half hosting Event Horizon, the most popular IsR player server. As such, I've been exposed to a tremendous amount of information and discussion of IsR systems, and I test many things extensively on my own.

By default, every ship has one power group, and every device that generates power and every device that consumes power is placed in it. You can create multiple power groups, and move devices from one group to another, but you can't place the same device in multiple power groups. Power groups also are entirely isolated from each other, with no movement of power between them, unless you use power transfer boxes (PTBs), which we'll come back to in a few sections. You can access the power group manager by pressing F4 in the ship editor. You can also move devices from one group to another using the engineering terminal in-game, though this is not recommended since the engineering terminal can't show you exactly where on the ship the devices are or which device you're moving.

The most common misconception about power groups is that you need to put solar panels, doors, and life support in a separate group to ensue they always have power, but the power priority system ensures that those devices always have whatever power is available, no separate group needed.

"The what system?"

IsR has power priority, where it will route power to key systems at the cost of less important ones. The exact ranking for every device isn't known (would require a fair amount of careful testing), but the general listing goes like this:

1. Life support, doors, teleporters
   
2. Warp (drawn from cockpit)
   
3. Shields
   
4. Other devices

"Yeah well, so what? My ship doesn't spontaneously explode if I have separate power groups."

There are a few key reasons, one is the efficiency loss of multiple groups.
Let's say you have three power groups, one for life support and doors, powered by solar panels and a capacitors; one for shields, powered by hydrogen generators; and one for warp and all other ship devices, also powered by separate hydrogen generators. As soon as the capacitor for the first group is fully charged, you're losing out on free solar power. For your second group, you need four times the generational capacity of the standard drain for the shields when they're first powering up. Generational capacity that could be provided by the third group when you're not warping.

"Yeah, but maybe I want to blow a bunch of resources in extra generators and fuel for no reason."

That is your prerogative, but there are additional consequences. When a generator is damaged, its max possible power output goes down. If you have a bunch of separated groups each with their own generators, as soon as one of those generators is damaged, that group is now running short. If all the devices are merged into one group, then your shields could draw on generational capacity normally reserved for weapons, your engines could draw on power normally assigned to mining equipment, etc.


(There's also power priority in the game deciding which devices to draw power from. You can somewhat change this through the use of PTBs {again, will be covered in a future section}, but otherwise it goes like this:

1. Solar {PTBs}
   
2. Nuclear Reactors
   
3. Hydrogen Generators
   
4. Batteries and Capacitors.

The following is all very "end game" info about ship building, none of this is necessary or recommended for new players. If you're still on your first few ship designs, feel free to skip this section entirely and come back to it at a future date.

The utility of power groups is derived entirely through the use of power transfer boxes (PTBs), often called fuse boxes. You place the fuse box in a group, and in-game you can select another power group for the fuse box to draw power from. There are four tiers of fuse box, each with their own cap on the max amount of power they can pull. There are no other downsides, so you don't need to use the higher tier fuse boxes if you don't intend to move a lot of power through them.

For most use cases, you're using the fuse boxes as a way to easily turn off all the devices connected to them, though there are a few use cases where you use the slider to limit the amount of power consumed by the group the PTB is supplying.

Limiting the drain caused by escape pods:
Escape pods have a total capacity of 15 million power, or ten T0 batteries. That's a lot of fuel being sucked down right away, and depending on how your ship is designed, it may cause drain you don't want as soon as the ship is built. Using the fuse box to limit or turn off the drain caused by escape pods helps mitigate this.

Adjusting scanner power:
When mining you only want a relatively few number of scanners, but when you're searching for signatures or scanning scout points you'll want more scan power. Using PTBs lets you cut power to your scanners when you're mining or mission running to save on fuel.

Adjusting thruster strength:
Adding cargo to your ship can significantly affect how it handles, so having enough thrusters to easily turn when loaded can make it spin like a top when it's empty, and vice versa. You can also manually turn individual thrusters and engines off from the cockpit, but placing your thrusters into their own group and using a PTB makes the process much simpler on a larger ship where you may have dozens of thrusters.

Controlling automated setups:
On a late game ship/station, you may have several automated setups already programmed to produce a given resource. By placing all the devices associated with that production chain into their own power group and supplying it with a PTB, you can turn off that group at a single point instead of moving to every device individually to turn them off. Devices with no power do not consume automation cards.

Overcoming the power priority system:
As mentioned earlier, PTBs are treated as solar power for their group, so if you want batteries to be drained before switching to hydrogen gens this is an option. PTBs also allow you to charge capacitors from batteries, as normally capacitors will not draw power if batteries are the only source available.