Energy is required for a wide variety of buildings to work with full efficiency. In most cases, a building that consumes Energy can be disabled to manage Energy usage.
Energy utilization is tracked at the top of the screen, rather than on the left, where most of the other resources appear and will be labeled "Wt". The value shown will be green if a surplus is being produced, red if an energy deficit exists, and orange if there is currently a surplus but will be a deficit when winter comes (due to weather-based production from Solar Farms) — note that this does not account for the effect of Cycles on Sunlifters or HR Harvesters. The tooltip will show the details of consumption and production.
If there is an Energy surplus, there is a bonus to certain effects. If there is an Energy deficit, there is a penalty to certain effects. No effects experience both a bonus and a penalty. Effects which experience a bonus are unaffected by an Energy deficit, and effects which experience a penalty are unaffected by an Energy surplus.
A surplus of Energy improves the effects of Broadcast Towers. The effect is dependent on the ratio of Energy production to Energy consumption, rather than the net surplus displayed. Both the Culture per Tick and Maximum Culture effects of Broadcast Towers are multiplied by this ratio, up to a maximum of 1.75 (for ratios higher than that, 1.75 is used). Both resulting effects are rounded down to the nearest integer. Rounding is performed before effects from Satellites with Satellite Radio. The Unhappiness Reduction is not affected.
A deficit of Energy results in a penalty to the production boosts from Magnetos, Reactors, Satellites, and Orbital Arrays. The effect is dependent on the ratio of Energy production to Energy consumption, rather than the net deficit displayed. The production boosts are independently multiplied by this ratio, with the ratio having a minimum of 0.25, before being multiplied together. The effects from Satellites and Orbital Arrays are treated as one effect. For example, a ratio of 0.5 with a 20% Magneto boost, 30% Reactor boost, 5% Satellite boost, and 10% Orbital Array boost would result in a (1+0.2*0.5)*(1+0.3*0.5)=1.265 multiplier to production for earth buildings instead of the normal (1+0.2)*(1+0.3)=1.56 multiplier, and a (1+(0.05+0.1)*0.5)=1.075 multiplier for space buildings instead of the normal (1+(0.05+0.1))=1.15 multiplier. An Energy deficit will never result in less production of regular resources than if no Magnetos, Reactors, Satellites, or Orbital Arrays were owned. In the case of an Energy deficit, Energy consuming buildings will continue to remain active, and their non-productive aspects will remain fully functional (e.g. space stations will continue to support 2 kittens).
During an energy deficit, Sunlifter will not produce antimatter.