Electric Heater Power Station Calculator

A resistive electric heater turns almost all of the power it draws into heat, and it draws that power continuously while it is on. There is no efficiency trick and no idle state: a 1,500 W heater pulls about 1,500 Wh from the battery every hour it runs.

• 1,500 W for 1 hour ≈ 1,500 Wh, before inverter and reserve losses.
• 1,500 W for 4 hours ≈ 6,000 Wh — more than most single power stations hold.
• 1,000 W for an 8-hour night ≈ 8,000 Wh.

For comparison, a phone charger and a few LED bulbs together might use 30–50 Wh in an hour. A heater is one to two orders of magnitude heavier. Running one from a battery is realistic for short, targeted warm-ups, not for continuous heating.

The energy side of this uses the same method as the main Power Station Size Calculator. Two specifications decide whether a power station can run a heater, and they are independent:

• Battery capacity, in watt-hours (Wh), is the stored energy — how long the heater can run before the battery is empty.
• Continuous AC output, in watts (W), is how much power the inverter can deliver at once. A 1,500 W heater needs an inverter rated for at least 1,500 W continuous, held for the whole run, or the power station overloads and shuts off.

Unlike a microwave, a heater stresses both: it needs a big inverter and a large battery, because it draws heavily for a long time. To see how long a given unit lasts against a steady load, use the Power Station Runtime Calculator. The same capacity-versus-output split applies to an air conditioner.

• Rating label. The plate on the base or back lists volts and watts or amps (amps × volts = watts). Many heaters show two figures, one per heat setting.
• Manual or manufacturer spec. Look for “rated power”, “power consumption”, or “wattage”, with the High and Low values.
• Watt meter. Plug the heater into a meter on each setting and read the watts — a measured figure, and the most reliable.

Common ratings are around 500, 750, 1,000, and 1,500 W, but do not assume yours: some personal heaters draw a few hundred watts, and a 1,500 W heater on Low may pull about 750 W. Size the calculator on the setting you will actually run.

Raw energy is just the input watts multiplied by the hours of use, before inverter efficiency and a reserve. Find your heater's wattage on its label — do not assume it.

High wattage does not always mean a huge watt-hour total. A 1,500 W heater run for only 10 minutes uses 1,500 W × 10 min / 60 = 250 Wh of raw energy — a small battery could hold that.

The output requirement does not shrink, though: for those 10 minutes the power station still has to deliver the full 1,500 W continuously. This is the case where the recommendation below can point to a larger class than your energy figure alone suggests: if your battery requirement fits the 500 Wh range but the smallest listed unit with a confirmed 1,500 W continuous rating is in the 1,000 Wh range, that is the class shown. The calculator's own size figure does not change — only the affiliate match moves up.

The same short-burst, output-limited pattern applies to a microwave.

It can. A heater with a working thermostat runs at full wattage until the room reaches the setpoint, then cycles the element off and on to hold it. Over a long run the average draw can be well below the nameplate wattage, so real energy use may be lower than watts × time.

How much lower is not predictable. It depends on the room size, how well it is insulated, the thermostat setpoint, the outdoor temperature, and drafts. A cold, leaky room on a freezing night may barely cycle at all. Because of that, this calculator uses full watts for the full time you enter as a safe baseline and does not apply a duty-cycle discount.

To model cycling, shorten the “use time” to the equivalent hours you expect the element to actually be drawing power — for example, entering 1.5 hours instead of 3 if you think it will run about half the time once the room is warm.

Briefly. A 1,000 Wh unit has roughly 650–800 Wh usable after inverter losses and a reserve:

• At 1,500 W, that is about 25–30 minutes.
• At 1,000 W, roughly 40–50 minutes.
• At 500 W on a small heater, around an hour and a half.

Whether it runs at all is a separate question. A 1,000 Wh unit with a 1,000 W inverter cannot sustain a 1,500 W heater; some 1,000 Wh-class units now ship with 1,500 W or larger inverters and can. Check the continuous AC output rating against your heater's input watts. If you also need to keep a fridge, lights, or a CPAP running, add them together in the Home Power Outage Calculator.

For output, usually yes: a 2,000 Wh power station typically has a 2,000 W or larger inverter, enough for a 1,500 W heater with headroom. Runtime is still short. With around 1,300 – 1,600 Wh usable:

• At 1,500 W, roughly 50 – 65 minutes.
• At 1,000 W, about 1.5 hours.
• At 750 W, a little over 2 hours.

That is a useful warm-up or a bridge through a short outage, not a full evening or an overnight. For longer heating you are into 3,000 Wh-plus units with expansion batteries, and the watt-hours add up quickly — check the numbers for your own heater and run time in the calculator above.

• Camping. A 1,500 W ceramic heater will flatten a portable power station in well under an hour, and needs an inverter that can supply 1,500 W continuously. A low-wattage personal heater used in short bursts is more realistic. The Camping Power Station Calculator sizes the rest of your setup.
• RV. Check whether the rig's onboard inverter is rated for the heater's watts and feeds the outlet you would use. The RV Power Station Calculator covers 12V and AC loads together. Propane or a diesel heater is far more energy-dense for sustained warmth off-grid.

Solar rarely keeps pace with a heater in real time — it is one of the heaviest loads there is. The Solar Charge Time Calculator shows how long a panel takes to refill the battery between uses. Another short but output-hungry resistive load is a hair dryer — the Hair Dryer Power Station Calculator sizes one on the same basis.

Electric resistance heating consumes battery capacity very quickly. A few hours or an overnight of heating easily runs into several thousand watt-hours — often more than a single portable power station holds. A large battery does not change the physics; put your real heater watts and hours into the calculator above and watch the recommended capacity climb.

For an outage, that usually means:

• Back up essentials first — medical equipment, the refrigerator, lighting, communication — and size those with the Home Power Outage Calculator.
• Use a heater in short, targeted bursts to take the edge off one room, not as continuous heat.
• Prefer a lower-wattage personal heater, and combine it with warm clothing, blankets, and closing off unused rooms.

A portable power station is a short-term bridge, not a replacement for a furnace or a whole-home heating system.

Check every item against your heater and your situation before buying:

• Heater input watts from the rating label or a watt meter, on the setting you will run — not an assumed 1,500 W.
• Continuous AC output (W) at or above the heater's input watts, with headroom. This decides whether it runs at all.
• Battery capacity (Wh) at least the recommended figure from the calculator for your run time — and expect that to be large.
• Usable capacity / efficiency the real watt-hours you get after inverter losses and a reserve, not the headline number.
• AC voltage matches the heater (most portable heaters are 120V; confirm yours).
• Outlet compatibility an AC outlet the heater's plug fits, on a pure sine wave inverter.
• Recharge time from wall, vehicle, or solar, so the unit is ready again after a heavy draw.
• Manufacturer operating limits for both the heater and the power station — clearances, ventilation, and temperature ranges.

A power station in the right range is a candidate, not a confirmation. Only its continuous AC output and real usable capacity, checked against your heater's watts and run time, tell you it will work.

An electric heater is a high-power load and a heat source. A few practical points:

• Do not exceed the power station's rated continuous AC output. An overloaded inverter shuts down, or runs hot.
• Follow the heater manufacturer's stated power supply and voltage requirements.
• Use the heater's own cord into a properly rated outlet. Avoid damaged, thin, or undersized extension cords and unapproved plug adapters.
• Keep the clearance the heater manufacturer specifies around and above the unit, away from bedding, curtains, and furniture.
• Follow the manufacturer's instructions on leaving a heater unattended or running it while asleep.
• Respect the power station's own ventilation and operating-temperature limits; a sustained heavy draw makes it work hard.

None of this makes a portable power station a safe substitute for whole-home emergency heating — it is a short bridge for one room.