What size power station do I need?

Size the job before the battery

The right station is the one that supports your priority devices for your intended time, with a realistic route to recharge. Start by writing down what must stay on and what can wait. Keeping communications, light and cooling available is a different job from recreating every household convenience. A short list also makes the result easier to verify against device labels and the exact station manual.

For each device, record quantity, running watts, starting watts where relevant, daily use and duty cycle. Add the planned outage or trip duration. Separate essential background loads from equipment you can schedule. A laptop charger can often wait while another flexible load runs; a refrigerator may restart without warning. The calculator’s scheduling toggle only works if you can actually manage the schedule you enter. It does not reduce the total energy needed for those daily hours.

The capacity formula, with the assumptions exposed

For device energy, multiply quantity by running W, hours and the active share of that time, then add the rows. The full calculation is shown on our methodology page. Our default 85% inverter efficiency and 20% unused reserve are editable planning choices, not facts about every battery. The efficiency allowance and reserve serve different purposes, so both appear explicitly.

Reserve is capacity you intend to leave unused. Dividing by the remaining usable fraction is different from merely adding the same percentage to the load. Battery-side inverter idle energy is added after converting the AC device load, avoiding another conversion allowance on that already battery-side quantity. If you do not know idle draw, the default omits it and the calculator says so. Do not interpret that omission as evidence that your chosen inverter consumes no energy.

Worked plans: outage, CPAP and camping

These are transparent arithmetic examples built from published typical device watts and explicitly chosen schedules. The schedules are not promises about how long your appliances should run. Each result applies the methodology defaults, omits idle draw and rounds upward for shopping capacity. Open the calculator to replace every assumption with your own plan.

The CPAP example is an energy illustration, not a medical-device backup recommendation. Heated humidifiers and tubing can change consumption, and the required power adapter may affect the complete system. Confirm a reliable backup arrangement with your equipment provider and clinician. A station that works as an occasional travel power source is not automatically an approved substitute for the battery system your therapy equipment requires.

Size classes are a navigation aid

We use the following editorial classes to make calculator results easier to scan. The boundaries are our own interface labels, not industry standards or guarantees about the appliances a station can run. In particular, a compact battery with an unusually strong inverter is still limited by its stored energy. An extended-capacity battery with a weak inverter can still reject a demanding startup.

Use the class to narrow a search after doing the load calculation. Do not work backwards from an attractive class label to an assumed runtime. The same advertised capacity can represent a generous trip plan for lights and device charging, or a brief bridge for continuous high-power use. Keeping the load list visible makes that difference concrete.

Usable energy is smaller than the headline

Energy stored in the cells is not identical to energy delivered through an AC socket. OutdoorGearLab reports 60–93% usable AC energy in its tested set. This is attributed research rather than a MySunSpark measurement. Its results support treating nameplate and outlet energy separately, but they do not establish a universal conversion efficiency for your load or station.

Very light loads, battery condition, temperature and automatic shutdown behaviour can make simple estimates less representative. Keep a reserve, document the assumptions and update the load list after observing your own equipment. Check that the station does not disable the relevant outlet when a cycling device rests. A correct daily energy total is not enough if an energy-saving mode turns off the socket before the appliance needs to restart.

Battery chemistry is part of a broader decision

LiFePO4 and NMC describe different lithium-ion battery chemistries. Chemistry alone is not a complete buying verdict: compare the exact product’s operating limits, retained-capacity warranty, mass, charging behaviour and service support. Avoid transferring a cycle-life claim from a brand’s newer product to an older station with a similar name. The battery management system and the rest of the design matter alongside the cells.

Both example models in our shortlist use LiFePO4 according to their EcoFlow product information and Jackery specification page. We do not turn that into an invented lifespan or a claim that either is the safest station in every setting. Read the operating and storage instructions, keep the equipment within its stated environment limits and arrange repair or disposal through an appropriate provider if the battery is damaged.

Plan the next charge as carefully as the first

A full battery is only the beginning of a longer trip or outage. Solar recharge is battery Wh divided by effective panel W. Effective panel output depends on your selected derate; solar days then depend on the peak-sun-hours input. Both are assumptions in our tool. The result does not represent uninterrupted wall-clock sunshine and does not include loads running during the refill.

Match the panel’s open-circuit voltage and current to the station’s specified input window, including any cold-weather allowance required by the manual. Check connector type and polarity rather than assuming that a physically fitting adapter makes a pairing safe. For a balcony installation, a grid-connected microinverter is a different system from portable DC panels. Use the balcony guide before deciding which kind of solar equipment belongs in your plan.

A shortlist, with limits you can inspect

Our calculator compares a small set of documented models instead of pretending to cover the market. The EcoFlow DELTA 2: 1,024 Wh, 1,800 W continuous, 2,700 W surge is the higher-continuous-output example of this pair. The Jackery Explorer 1000 v2: 1,070 Wh, 1,500 W continuous, 3,000 W surge is the higher-surge example. Those labels describe a specification comparison, not testing awards.

Neither is automatically the correct size for every worked scenario. A model may pass continuous and surge demand while failing the energy requirement for your chosen duration. Open the model checks in the calculator to see the shortfall rather than stretching the assumptions until a favourite product turns green. Prices change, and regional output specifications may differ. Confirm your local variant before purchasing.

Questions, answered