Energy

Energy is what makes your mines run. It is not a resource. You cannot store it, spend it, ship it or have it plundered, and it does not appear in the resource bar at the top of the screen. Every planet keeps its own energy books: the mines on it need a certain amount per hour, the power plants and satellites on it produce a certain amount, and if production falls short every mine on that planet slows down. You only ever see the numbers on the Buildings page.

What happens when you are short

Efficiency = energy produced ÷ energy the mines want, capped at 100%.

That one percentage is applied to every mine on the planet. It is not first come first served and it is not worked out per mine, so one oversized Hydrogen Synthesizer will drag the Ore Mine and Crystal Mine down with it.

The planet above produces 5,315 energy and its mines want 7,164, so everything runs at 74%. The Ore Mine is level 22 and should make 10,784 ore an hour. It makes 8,011. The Crystal Mine and the Hydrogen Synthesizer take exactly the same cut.

The Buildings page shows this in three places:

The Energy panel in the sidebar. Watch out for the bar: the "Used" figure is capped at what you actually produce, so on a short planet it reads 5,315 / 5,315 and looks fine. The real shortfall is the "1,849 energy needed" line under it.
Each mine row, which shows "Production: what you are getting of what you should get" and "Energy: what the mine is getting of what it wants".
A red Insufficient Energy warning, which appears on every mine on the planet at once.

The one thing a shortage never touches is the free trickle. Every planet makes 40 ore and 20 crystal an hour no matter what, even with no mines and no power at all.

That leads to the most common new player mistake in SFC2. A new planet starts with no mines and no Solar Array. If you build the Ore Mine first, it wants 11 energy, the planet produces 0, so efficiency is 0 and the mine produces nothing at all beyond the free 40 an hour you were already getting. Build a level or two of Solar Array first, or alongside.

What uses energy

Only mines. Buildings, the Shipyard, defenses, ships parked in orbit and research all cost nothing to run. The in-game description of the Solar Array says it powers "your mines and buildings", but buildings are free.

Ore Mine and Crystal Mine: 10 × Level × 1.1^Level, rounded down, plus 1 once the mine is past level 1.
Hydrogen Synthesizer: 20 × Level × 1.1^Level, rounded down, plus 1 once past level 1.

So the Hydrogen Synthesizer costs twice as much power as the other two at the same level. On a planet with all three mines at level 22 the synthesizer alone is 3,582 of the 7,164 bill, half the total. If a planet is starving, that is the first place to look.

A full store does not free up any energy. When a mine hits its warehouse cap it stops producing but keeps its place in the energy sum, so the other mines get no more power than before.

Where energy comes from

Solar Array

The default source and the one every planet builds first. Energy = 20 × Level × 1.1^Level, rounded up. Nothing to run and nothing to feed it. It costs 75 ore and 30 crystal for level 1 and multiplies by 1.5 for every level after, and each level uses one field.

Nuclear Power Plant

Needs a Hydrogen Synthesizer at level 5. It also lists Energy Tech 3, but every player starts with Energy Tech 3, so in practice the synthesizer is the only gate.

Energy = 30 × Level × (1.05 + 0.01 × Energy Tech level)^Level, rounded up.
Hydrogen burned = 10 × Level × 1.1^Level, rounded up, then doubled.

That hydrogen comes off the planet's stock every hour whether you need the energy or not, and it does not stop when the plant is producing more energy than the mines can use. A level 12 reactor eats 754 hydrogen an hour forever. Check the Production panel on the Buildings page, which breaks the hydrogen line out into what the synthesizer makes and what the reactor takes.

Helios Class Solar Satellite

A stationary ship built at the Shipyard, not a building. Energy = max temperature ÷ 4 + 20, rounded down, per satellite. Costs 2,000 crystal and 500 hydrogen each and uses no fields. See Helios Class Solar Satellite.

Genesis Solar Satellite

The premium version. 10,000 credits each, no resources. Energy = max temperature ÷ 2 + 40, rounded down, so exactly double a Helios, and it has a 70% chance of coming back after being destroyed. See Genesis Solar Satellite.

Temperature and satellites

Both satellites pay out on the planet's maximum temperature, which you can read on the Overview page under the planet's name. Temperature is set by the slot number: the low slots are hot and the high slots are cold. Actual values wander a few degrees either side of the base.

Slot	Max temperature	Helios each	Genesis each
1 to 3	about 90°C	42	85
4 to 6	about 65°C	36	72
7 to 9	about 40°C	30	60
10 to 12	about 0°C	20	40
13 to 15	about -45°C	8	17

This runs the opposite way to hydrogen, which pays more on cold planets. An outer colony makes plenty of hydrogen and gets very little out of satellites, so it usually leans on power plant levels instead.

Energy Tech and the reactor

Energy Tech is the only research that changes energy output, and it only touches the Nuclear Power Plant. It replaces the growth base in the reactor formula: 1.05 at level 0, 1.06 at level 1, and so on.

That matters more than it looks. At Energy Tech 5 the base hits 1.1, which is the same curve the Solar Array uses, but with a multiplier of 30 instead of 20. From that point the reactor beats a Solar Array of the same level and keeps pulling away. Below Energy Tech 5 the reactor grows slower than solar and a same-level Solar Array eventually overtakes it: at Energy Tech 3, the level every player starts with, that happens at level 23.

Energy Tech	Nuclear Power Plant level 15
3 (starting level)	1,428
5	1,880
8	2,815
10	3,662
12	4,743
15	6,934
20	12,790

A Solar Array at level 15 makes 1,254, for comparison, and it burns nothing.

Energy Tech costs 800 crystal and 400 hydrogen for level 1 and doubles every level after. Most players have a good few levels of it long before they ever build a reactor, because it also unlocks Pulse Drive and Jet Drive at 1, Laser Tech at 2, Shield Tech, the Pulse Cannon and the Zagreus Class Recycler at 3, Particle Tech at 4, FTL Tech at 5, the Gauss Cannon at 6, Plasma Tech at 8 and the Zeus at 11.

The More Info button on the reactor lists the next few levels with the energy and the hydrogen side by side, worked out at your current Energy Tech.

What energy costs

Power plant levels get exponentially more expensive. Satellites never do. That gives a crossover point, and it arrives earlier than most people expect.

The numbers below convert everything to ore using the Trade Merchant's rate (1.5 ore to 1 crystal, 2.5 ore to 1 hydrogen) so the three sources can be compared. A Helios works out at 4,250 ore-equivalent whatever planet it is on, but the energy it gives depends on the temperature.

Planet	Helios energy each	Cost per point of energy	Solar Array level where satellites get cheaper
about 90°C	42	101	13
about 65°C	36	118	14
about 40°C	30	142	15
about 0°C	20	213	16
about -45°C	8	531	19

For scale, going from Solar Array 14 to 15 costs 21,895 ore and 8,758 crystal and buys 190 energy. Going from 19 to 20 costs 166,263 ore and 66,506 crystal and buys 366. Eight Helios cost 16,000 crystal and 4,000 hydrogen and buy 240 on a 40°C planet, and they will still cost that when your Solar Array is level 30.

The Nuclear Power Plant is the dearest of the three per point of energy, and it charges hydrogen on top. What you actually buy with it is fields. At Energy Tech 15 a level 12 reactor makes 3,210 energy off 12 fields. Getting that from Solar Arrays alone takes level 21, which is 21 fields. The reactor costs a bit over twice as much to build and 754 hydrogen an hour to run, and what it hands back is nine fields on a planet that has run out of room.

The catch with satellites is that they are ships sitting on your planet. 200 hull, 1 shield, 1 weapon, and every ship in the game has rapid fire against them. One raid wipes out the whole satellite fleet, your mines drop back to whatever the power plants alone can carry, and the wreck leaves crystal debris for the attacker to harvest on the way out. Power plant levels cannot be taken off you.

Most players end up doing both: enough Solar Array levels that a raid does not shut the planet down, and satellites stacked on top for the cheap headroom.

The capacity setting

Every mine and every power plant has a Capacity dropdown running from 0% to 100% in steps of 5. On a mine it cuts output and energy draw by the same percentage. On a power plant it cuts the energy produced, and on the Nuclear Power Plant it cuts the hydrogen burn to match.

It is the fix for a reactor you built too big and can no longer feed, and for a planet where you would rather put the power you have into the Ore Mine than the Hydrogen Synthesizer.

Energy by level

Solar Array energy is what one plant at that level produces. Cost is what that single level costs to build. Mine energy is what a mine draws at that level, at 100% capacity.

Level	Solar Array energy	Ore cost	Crystal cost	Ore or Crystal Mine draw	Hydrogen Synthesizer draw
1	22	75	30	11	22
2	49	113	45	25	49
3	80	169	68	40	80
4	118	254	102	59	118
5	162	380	152	81	162
6	213	570	228	107	213
7	273	855	342	137	273
8	343	1,282	513	172	343
9	425	1,923	769	213	425
10	519	2,884	1,154	260	519
11	628	4,325	1,730	314	628
12	754	6,488	2,595	377	754
13	898	9,731	3,893	449	898
14	1,064	14,597	5,839	532	1,064
15	1,254	21,895	8,758	627	1,254
16	1,471	32,843	13,137	736	1,471
17	1,719	49,264	19,706	860	1,719
18	2,002	73,895	29,558	1,001	2,002
19	2,325	110,842	44,337	1,163	2,325
20	2,691	166,263	66,506	1,346	2,691
21	3,109	249,395	99,758	1,555	3,109
22	3,582	374,092	149,637	1,791	3,582
23	4,119	561,138	224,455	2,060	4,119
24	4,728	841,706	336,683	2,364	4,728
25	5,418	1,262,559	505,024	2,709	5,418

Odds and ends

Moons have no mines and no power plants, so energy never applies to them.
A deployed Hephaestus platform does not mine either, so it has no energy figures.
Diplomacy Mode and Vacation Mode cut or stop production, but they change nothing about energy.
Tearing down a mine level gives back the field and the energy draw. Tearing down a power plant level gives back the field and takes the energy away.
Energy is worked out per planet. There is no sharing between your planets and no alliance help with it.