Solartopia: what solar power makes possible

In the first level of Solartopia you light a village of 1,200 people with four crates of solar panels, and you decide when to run the water pump. The real problem behind it is large. About 666 million people had no electricity in 2023, and most of them live in sub-Saharan Africa. Without power there is often no pump, and without a pump someone walks to the water.

Solar panels suit a pump well, because a pump does not mind when it runs. It can fill a tank at noon, when the sun is strongest, and the village drinks from the tank all day. That is why the game asks you to time it.

Day two is a clinic fridge. Vaccines must stay cold around the clock, so the fridge is a job that cannot wait for the sun. In the game you solve it with a battery jar.

Solar vaccine fridges use a neat trick: they store the sun's energy as ice, and the ice keeps the vaccines cold through the night. The game gives you a battery jar instead, because a jar is easier to see. The wider problem is still big: many clinics have power that cuts out, or no power at all.

Day three is a school with laptops and an internet link from nine to three, and evening study lights from six to nine. These jobs run on a fixed schedule, so the sun alone cannot carry them. You need two battery jars, and the jars need to be full by sunset.

A school with power and a connection can give a child a place to get online when there is none at home. That is why the game treats school hours as a promise: the power has to be there at nine, and again after dark.

Day four moves to a town of 12,000 people and a field that needs watering. Irrigation draws a lot of power, and in the game a cloud bank drifts across the left half of the map at midafternoon. You learn to water in the morning and leave the afternoon for the jar.

Irrigation matters because watered land grows much more than its share of the farmland. The figure we use comes from an older FAO booklet, so treat it as a rough guide, not a current count. A pump that runs on sunlight only needs the sun to be up, so the game asks you to do the watering while it is.

The last level is a city of 400,000 people and a depot of electric buses. Each bus needs far more power than a pump, so charging time is the whole puzzle. Charge them at noon and the jar stays full. Charge them at midnight and the jar runs dry before morning, which is the trap.

Real cities have done this at scale. Electric buses also take the exhaust out of the street, which matters because almost everyone breathes air that is dirtier than the World Health Organization recommends.

The reason Solartopia is even possible is price. New solar farms now produce electricity at a fraction of their cost in 2010, and in 2023 IRENA found they cost 56% less than the least-cost new fossil-fuel option, on a weighted average. Batteries followed the same curve, which is what lets solar power the night too.

Cheaper panels and batteries are why a village can afford four crates of panels in the first place. They are also why the game gives you more crates each day.

Solar is not the whole answer. It made about 7% of the world's electricity in 2024. It makes nothing at night, and less in winter and under clouds. The rest of the grid still has to cover those hours with batteries, wind, hydropower and strong power lines.

That is why, from day two on, the game needs a battery jar as well as panels. You have to work with the sun, and with the jar. Real grids do the same, at a much larger scale.

At the end of the game you choose a state and a goal for your own home: a smaller bill, lights on when the grid goes down, or driving on sunshine. Rates, sun and rules differ a lot by state, so the figures come from our state data. You can also open the state pages directly, or use the solar, battery and EV calculators.

Start with your state's energy page, then try the plug-in solar guide, the solar calculator, the battery sizer or the go-electric planner. The 30% federal tax credit for home solar and batteries has ended; see what is still available.

The sun follows a smooth daytime curve: nothing at night, a peak at noon. A panel in the shade of the mango tree makes half as much, and a panel under a cloud makes a quarter. A battery jar returns 90% of what you put in, so a little is lost each time. The jar starts the first two days half full and the last three a quarter full, so you leave it as full as you found it. A breaker switches the flexible jobs off if the jar runs low, to protect the clinic.

We simplified on purpose. You get crates, not dollars, because real prices differ by place and year. Every panel is the same size, every job draws a steady amount, each day is 24 game hours that last about 24 seconds, and from day three the tank has to be full by 3 pm. The facts are real and linked below, but the game is a model, not a design tool for a real village.