Its description reads: "Produce more than 10 GJ per hour using only solar panels."
I am aware that this achievement has changed a bit throughout the course of development. Before the existence of nuclear reactors, it was saying something like "without the use of steam engines" instead of "only solar panels".
My problem is twofold:
edit: I had to fix my math. Thx @boskid for the hint. Was assuming wrong solar panel power. It is 60kW max power per solar panel. Corrected numbers are underlined. And an additional insight: more power is needed to recharge the accumulators during the day. But this issue is not about the actual math. It is about the phrasing. Or "locale" as Rseding called it. I thought the English locale was part of the base game, but anyways.
- "10 GJ per hour" is a rate of energy production which is identical to about 2777.7778 kJ per second also known as 2777.7778 kW. This is what you get from about 47 solar panels producing at max rate during daytime. But it is clearly not what you mean. If I interpret the game's behavior correctly, you mean something like "10 GJ in one hour", which is the required total produced electric energy. That means you have to have the 47 solar panels run for at least one hour. Since one hour is several day & night cycles, you need to get concerned about nighttime. During dusk & dawn solar panels produce less power, at night none at all. So you need more solar panels than just 47, and even more to recharge the accumulators. And without power production at night you need steam engines / accumulators / steam turbines to keep your base running.
- I was very uncertain whether accumulators are considered power producers for this achievement. In the game's terminology there are only power consuming entities and power producing entities. You can see them in your electric network statistics. Accumulators appear in both statistics, so they appear to be both consuming and producing power. I was seriously considering setting up an electric network separate from my main base with only solar panels and some permanent consumers like beacons and radars and to have it run for one hour (while being dead at night). But the achievement triggers as soon as your electric network statistics for the last hour shows a total produced power of more than 10 GJ, with the energy producers being a mix of solar panels and accumulators. This is way easier than only solar panels, especially if your base reaches a certain size and is running mostly on solar panels anyways -- for reduced pollution. You Just need to turn off steam engines (permanently or with circuit control) to drain the accumulators instead of running steam power. One hour spans over several in-game day & night cycles. Therefore it is perfectly reasonable to allow accumulators for this achievement. How about making this intention a bit more explicit?
- "Produce more than 10 GJ in one hour using only solar panels and accumulators."
- "Produce more than 10 GJ in one hour using only solar panels (and accumulators)."
- "Produce more than 10 GJ in one hour without the use of steam engines nor steam turbines."
- "Produce more than 10 GJ in one hour without the use of steam power."
I don't care much about the achievement triggering in modded playthroughs. Since some people may care about it, I would use the one that is closest to the game's actual checks.