What is The Long Dark Season?

A free browser-based off-grid power survival simulation. You manage a battery bank, solar array and appliance loads through ninety days of worsening weather. Each day you choose what to run; the battery charges and depletes on real electrical math. Run out of stored energy and the run ends. Progress is saved locally and permanent upgrades carry between runs.

Yes. No account, no payment, no advertising and no in-game purchases. Progress saves automatically in your browser.

Does the game use real off-grid power calculations?

Yes. Solar generation is array watts multiplied by sun-hours and derated 25 percent for heat, wiring and angle, exactly as in our Power Sizer. Battery capacity is amp-hours multiplied by system voltage at 90 percent usable depth of discharge. MPPT controllers harvest roughly 25 percent more than PWM. Heating load scales with outside temperature and insulation level.

Survive ninety days from late autumn to spring without the battery bank reaching zero. Most players fail early runs in the first two weeks. Salvage earned from each run buys permanent upgrades to battery capacity, solar array, charge controller, insulation, alternator charging and heat source, which make later runs survivable.

Free · no account · saves in your browser

The Long Dark
Season.

Ninety days from late autumn to spring. One battery bank, one solar array, and a forecast that gets worse before it gets better. Every day you choose what runs — and every choice is priced in watt-hours on the same math the Power Sizer uses. Let the bank hit zero and it is over.

Day1

To spring90

Bank100%

Harvest0 Wh

Load0 Wh

Net0 Wh

Work days0

Salvage0

100%

—

— —

—

01 Loads — what runs today

02 Field log

The math is real

This is not a made-up simulation.

Every number here is the same math behind the Power Sizer. Solar generation is array watts × sun-hours, derated 25% for heat, wiring, angle and controller loss. Battery capacity is amp-hours × voltage at 90% usable. A PWM controller throws away roughly a quarter of what your panels make; MPPT does not. Heating load scales with outside temperature and drops with insulation.

That is why the failure teaches something. When your bank dies on day 19, it is not bad luck — it is because you spent your budget on storage instead of harvest, or skipped the insulation, or ran Starlink through a week of overcast. The build decided it before the storm arrived. That is a real mistake people make with real money.

How it plays

Three decisions up front, then ninety days of consequences.

Pick your rig. A tent has nothing to power but no roof for panels. An RV has the most roof and the biggest appetite. Roof area is a hard cap on how much solar you can mount — about 18W per square foot.
Pick your season. Late autumn is the standard run. Deep winter drops you into the worst of it and pays 1.7× score. Early spring is the gentle way in.
Spend your build budget. Battery, solar, MPPT controller, insulation, diesel heater, alternator charger, inverter. You cannot afford all of it. That is the point.

How to actually survive

Efficiency beats capacity. Insulation and a diesel heater cost less than the battery you would need to cover the heat you lose. Reducing demand is always cheaper than adding supply — same as real life.
MPPT is usually the best value on the board. It harvests roughly 25% more from the same panels for a fixed cost.
Balance storage against harvest. All battery and no panels means you are spending down a bank that never refills. All panels and no battery means a good day is wasted because you have nowhere to put it.
Read the forecast before you commit. Three storm days coming means shed loads now, not at 20%.
Working needs the laptop and Starlink both on — and Starlink is heavy. Income versus reserve is the tension you manage every single day.
You are meant to lose early runs. Salvage buys a bigger build budget, and a bigger budget is a better system next time.

Size a real system free Read the field notes

The Long DarkSeason.

Pick your rig.Build your system.