Watt Hours To Amp Hours Conversion (Wh To Ah): Calculator + Chart

Watt-hours and amp-hours are both units for electric charge.

1 watt-hour is defined as 1 watt of power expended for 1 hour.

1 amp-hour is defined as 1 amp of current expended for 1 hour.

How do you convert watt-hours to amp-hours?

It is possible to convert watt-hours to amp-hours using the following formula:

Watt-hours = Amp-hours × Volts

To calculate amp-hours from watt-hours, we need to rearrange this equation to:

Amp-hours = Watt-hours / Volts

For the watt-hour to amp-hour conversion, you also need voltage (V).

Here is a nifty amp-hour calculator that converts watt-hours to amp-hours. Further on, you’ll also find a chart of Wh to Ah for 120V and 220V. You can also check the battery amps hours chart for 12V and 24V batteries here.

Wh To Ah Calculator


Watt-Hours To Amp-Hours Conversion Chart

Watt-Hours (Wh) Amp-Hours (at 120V): Amp-Hours (at 220V):
1 Wh 0.008 Ah 0.005 Ah
10 Wh 0.08 Ah 0.05 Ah
20 Wh 0.17 Ah 0.09 Ah
30 Wh 0.25 Ah 0.14 Ah
40 Wh 0.33 Ah 0.18 Ah
50 Wh 0.42 Ah 0.23 Ah
100 Wh 0.83 Ah 0.45 Ah
200 Wh 1.67 Ah 0.91 Ah
500 Wh 4.17 Ah 2.27 Ah
1000 Wh 8.33 Ah 4.55 Ah

You can also do the reverse conversion. To help you out, we have created a similar Ah to Wh converter here.

Note: Due to low battery capacity, it’s quite hard to produce battery-powered HVAC appliances such as air conditioners, furnaces, heaters, and so on. It might be interesting to read our articles about battery-operated heaters here and battery-powered air conditioners here.

Battery capacity also plays a key role in the mileage of electric vehicles. For example, if you check our article about how long it takes to fully charge a Tesla, you will see that all Tesla battery capacities are expressed in kWh and not in kAh or Ah.

103 thoughts on “Watt Hours To Amp Hours Conversion (Wh To Ah): Calculator + Chart”

  1. if i have one appliance that draw 350 watts at 120 volts and i use a 100 amp hour lutetium battery will it last me 34 hour if drained 100% or am i figuring something wrong

    • Hello William, that appliance draws about 3 amps (350W/120V = 2.9 amps). 100 amp hours battery will supply 1 amp of electrical current for 100 hours. Or, as in your case, it will provide 3 amps for about 34 hours. That’s the basic logic. That does presume that your voltage is 120V; however, most batteries have 12V voltage. That will increase the electrical current you need to use to generate 350W by 10. That means that draw will be 30 amps; and the battery will last only 3.4 hours.

        • Hello Alfred, factor 10 comes from different voltages, 120V vs 12V, the ratio is 10. 200 Ah battery has lifepo4 4 cells with about 3V voltage each, bringing the total to 12V. 110W consumption is probably on 120V; it runs on 110W/120V = 0.92 amps. You calculate 200 Ah / 0.92 A = 217 h. The 110W device should drain the battery in about 217 hours.

          • Quick question, the 0.92 amps consumption is relevant to 120V – on the 12V battery, wouldn’t the consumption ramp up to 9.2A to generate 110W in this example? (Factor of 10 correction)

            So wouldn’t the battery only last 21.7 hours rather than 217 hours?

          • one comes to these forums seeking professional and knowledgeable people, i can tell unequivocally from the get go that the question was formulated wrong.
            ” have 200ah lifepo4 battery and 110w consume. How long will it drain the battery?”
            there must be something wrong right there. 110w consume what? instantaneous or over 24 hours? 100wh or just watts.?

          • Hello Francis, usually these questions are formulated like this: How long can I use a 200Ah battery to run a 110W electric device? If we know that a 200Ah 12V battery holds 2,400 Wh of electricity. If you run a 110W unit for 1 hour with such a battery, you are left with 2,290 Wh. Namely, you can calculate after how many hours the battery will be drained completely.

    • NEVER run your battery down more than 50% (35% is better) because you’ll kill your battery to a point that it can’t recharge after a few times. Recharging should kiick in at about 35% of power. A 12 v batter has different ratings – and some batteries are designed for enough power to turn the engine over, charge up and that’s it. RV batteries (probably like the battery in these AGM or LIPO) can be recharged more times but only if you don’t drain them below 50% max or you’ll have to buy a new battery soon. And the LIPO’s have built in controllers to protect them from catching fire – they don’t like heat or cold extremes.

  2. If I have a small solar panel capable of 30w optimally, and a portable fridge that operates at an average 0.89ah/Hr @12v that works out to 0.89×12= 10.86 w/hr, does that mean the 30w panel could operate the fridge without assistance from an external battery source, given the panel is in direct sunlight conditions for the hours needed to operate in the day time? If so, then even at half solar output (15w) it would still manage to operate the fridge? Thanks

    • Hello John, your calculations are on point. If your solar panel can provide 30W of power, it will run a 10.86W fridge. Even at the half output, it should be enough.

      • As long as the battery or solar panel match the voltage requirement of the fridge. If the fridge is a 12vdc model and needs 11W then it would be possible to run off the 30W solar panel. That is assuming it is not an inductive motor. If it is an inductive motor, then you will need a battery to take up the surge current during startup.

        If the fridge is a 120vac then no way will a 30w solar panel would work, A 12vd to 120vac inverter has about 80% efficiency. Even then it would also need to be a “True Sign wave” or the fridge inductive motor will run hot.
        So that being said: 120vac @ 11W would require a 12v (11W*10)*120%=132W panel with a battery for surge inrush from the inverter draw when fridge turns inductive motor on.

  3. I am looking at electric bicycles. One bike I’m looking at has a 960wh battery and a 1200watt motor, and the other one has a 52v 19.2ah battery and a 1000watt motor. I can’t tell which one is better. Help!

    • Hello Jasmine, an interesting question. So, the key here is to calculate the battery of the second bike. You have to multiply 52V and 19.2ah and you get 998.4wh. The first bike has a more powerful motor but shorter battery life. The second bike has a less powerful motor but a better battery life. Hope this helps.

  4. Hello, I’m looking at buying the ICECO VL60 dual Frig and Freezer that draws 45w and I have a 300w of solar panels to a 100AH Lithium Iron smart battery. The only other draw is from 3w LED lights and a 3w fan for my composting toilet. Can my system handle the ICEO? Thanks


    • Hello Andrew, if your solar panels continually provide 300 watts of power, you can it can easily handle 45W + 3W + 3W = 51W of power draw. Of course, the problem is that solar panels don’t continually provide 300W.

      Let’s say that power flow drops to 0W during the night. For how long can the 100 Ah battery provide power to appliances with the combined wattage of 51W? Well, 100 Ah battery probably has 12V voltage; that means that at full capacity, the battery stores 1,200 Wh. 1,200 Wh / 51W = 23,5 hours. That 100 Ah battery can provide power to the whole system (freezer + LED lights + fan) for about 24h.

      All in all, the system can handle the new freezer. Hope this helps.

        • The 50% discharge concern only applies to lead acid batteries. Lithium Ion batteries can be drawn down to 0% (or close to it) repeatedly without damage. That is one of the HUGE advantages of Lithium Ion batteries. That, and they are 1/3rd the weight, they charge more quickly and their output is more constant over time. Even their cost is only a disadvantage when considering the initial purchase. But since they last 3 to 5 times longer than lead acid batteries (up to 10 years or more), even that is not a disadvantage. And that is assuming the lead acid batteries are properly cared for. If people don’t don’t follow the 50% discharge warning you mentioned, they will last even less time (perhaps only 2 years).

          • Remember, when you refer to Lipo batteries “can be drawn down to 0%” This would be no more then 3.75vdc per cell. In real voltage terms it would be 89% of full charge. Once you start discharging down to 75% the cells start giving off gasses and swell. Also, Lipo needs to be stored at ~ 3.8vdc to last the longest when not used. They do not do well when stored charged or discharged. 0% is a meter reading that is made to make people understand discharged state. it is not reality.

  5. Hello,
    Could I ask a question please? I have two leisure batteries that each have 95amp/h or 1140 watt hours.
    I have a cool box, in the information leaflet it details the consumption as 55w on 12v. Does that mean 55w per hour? I can’t find anything to indicate an hourly rate.
    If so then does that mean that I could run that cool box for just over 41 hours?
    Thank you.

    • Hello Trish, two batteries combined have a capacity of 2280 Wh (at 12V). The cool box runs on 55 Watts; it will drain 55 Wh (every hour). That means that the cool box will run for 2280 Wh / 55 W = 41.5 hours; as you have correctly calculated, well done!

    • Hello Bassey, for every conversion, you also need voltage. Let’s say you have a standard 12V battery that produces 338W output. That means the battery generates 338W / 12V = 28.2 amps. That would mean that 338 Wh is equal to 28.2 Ah. Hope this helps.

    • Hello Bailey, 1000W for 5 hours is equal to 5 kWh. Batteries have 12V voltage; in this case, you would need a 416.67 Ah battery. Such a battery has an 83.3 amp output. For 3000W, you just multiply these numbers by 3 and you get the numbers.

  6. Hi, I would like to ask the following
    I’m looking to buy a power station for emergency power outage in the winter.
    Specifically, I’m planning to use a 1500W room heater for 8hr in such setting, which I haven’t found one yet, but I did find a power station stating 1260Wh with some 120V 15amp outlets. I’m confused as it also said “AC inverter output: 1800W continuous.”
    So would this power station good enough or I may need a bigger capacity one.

    • Hello Brooks, first you need to check if the output wattage is sufficient (at least 1,500W). The 120V 15amp output generates 120V*15A = 1,800W. This checks out, great. Now, 1,260 Wh means that such a power station can provide 1,260W wattage for 1 hour. You can power a 1,500W for about 50 minutes. So, not 8 hours. This is a very small power station; you would need a bigger one.

  7. hi im buying a beer bike and am looking to install a draft beer machine

    its 1.5a 220v
    the battery which comes with the bike is 60v – 80ah
    the motor for the bike is 3500watts

    my question is would I be able to run the machine and bike for roughly 6-8hrs or will I need to install another battery

    thank kindly


    • Hello Ian, cool gig. Let’s calculate a bit; the draft beer machine will run on 1.5A*220V = 330W (operating at 100% capacity). The battery has 60V*80Ah = 4,800 Wh capacity. With this, you can run the machine at 100% capacity for 14.5 hours, or a bike at 100% capacity for 1.37 hours. Now, the bike doesn’t operate at 100% capacity (3,500W) all the time; it operates at a significantly lower output. It’s very hard to say what the actual average draw will be. In order for the battery to last for let’s say 6 hours, the new wattage draw should be 800W. That’s 330W for the machine and 470W for the bike. These are the kind of calculations you can make but, in practice, the output is nearly impossible to figure out. Hope it helps a bit.

    • Hello Darren, the 1,700W appliance runs on 1,700W / 240V = 7.1 amps when running at 100% capacity. With a 240 Ah lithium battery, you can run it for 240Ah / 7.1A = 33.8 hours. Hope this helps.

      • Hi I’m looking to run a 4000 watt led p 4000 viperspectra for 24 hours a day for my chilli germination room
        What inverter?
        Battery ?
        And panels? will be sufficient pls

        • Hi there, well, running 4000W for 24 hours per day will require massive batteries; you are looking at 96 kWh per day. That’s… that’s a lot. Tesla Model 3 has a 75 kWh battery, for comparison. So, batteries are not a good idea here; you should just use the grid. Hope this helps.

    • I see an ad for a Chinese power station says 4000 watts 2611 wh it’s cost is $2800…how long will that run a 750 watt load please

      • Hi James, if we say these are lithium batteries with 100% discharge rate, you can look at it in this way: The power station has 2,611 Wh of capacity and you are running a 750 W load. You can calculate how long with this power station power the 750 W device like this: 2,611Wh / 750W = 3.48h. So, about 3 and a half hours. Hope this helps.

  8. Hi, I am trying to power a LCD screen using a portable power bank and would like to know what size battery I need to power if for 6 hours.

    The screen runs at 130mA at 12V apparently, so 1,560 mW.
    This equates to 1.56 Wh
    So, 1.56Wh x 12V/1000 = 130 mAh per hour
    => 130 * 6 = 780 mAh

    This doesn’t seem right. Can any help please?

    • Hello Alex, your calculations are on point. Both the LCD screen and the portable power bank run on 12V. If the screen draws 130 mA, you need a 130 mAh power bank to run it for 1 hour. If you want to run it for 6 hours, that’s a 780 mAh power bank. That LCD, as you have correctly calculated, really requires minimal input power; 1.56W. That’s why even a small power bank can run it for so long.

  9. Yea man you have helped these people a lot. I read all of them. Not sure why because I am very familiar with the formulas. But props to you for being so kind. I hope your at least making money from the ads on this site ….

    • Hello Sunday, have you tried using the calculator above? Here’s how you can do it manually: 532.8 Wh / 12V = 44.4 Ah. Alright, for an 80W appliance, you have to use watt-hours. Here’s how you do that: 532.8 Wh / 80 W = 6.66h. You will be able to run an 80W for a little less than 7 hours. Hope this helps.

  10. I have a Northstar NSB12-730RT battery.

    I was using your calculator and it seems my battery capacity is higher than I originally figured, can you check my math.

    Battery states 731 watts per cell at 4C rate.
    12v cell means 4386wh of power.
    Converted to ah = 365.5AH at 4C??

    I thought this was a 200-220AH battery.

    • Hello Jason, here’s how you can look at this. If a 12V battery states that it can produce 731W, that means it will generate 731W/12V = 61A of current while generating 731W. That’s not an indicator of battery capacity; it’s an indication of battery power output. The key difference (if you want to calculate capacity) is how long can a battery sustain this power output.

      Now, if you check the Northstar NSB12-730RT battery specs, you can see, for example, that this battery can generate 279W of electricity for 1h (at 1.75V discharge). That means that the battery contains 279Wh worth of electricity. How many Ah is that? Well, we have 1.75V voltage from the specs, so 279Wh / 1.75V = 160Ah. That means that you don’t have a 200-220Ah battery; you have a 160 Ah battery.

      I hope this makes sense, if not, just comment away and we’ll try to explain a bit more in-depth how all of these calculations work.

  11. I have a 12VCD motor at 30W which will run at 50RPM’s and a torque of 6N.m (just in case this info will help). Most of the time, I will run it for an hour. However, I do want the capability to run it for 8 hours continuously. What battery should I consider?

    • Hello there, thanks for sharing all the info. To calculate the battery size you only need the wattage (30W) for Wh sizing and voltage (12V) for Ah sizing. Basically, if you want any 30W motor to run for 8 hours, you need 30W * 8h = 240 Wh battery. Now, battery capacity is, in most cases, expressed in amp-hours (Ah). Here’s how you calculate amp-hours: 240Wh / 12V = 20 Ah.

      You would require a 20Ah 12V battery, or larger. Hope this helps.

    • Hello Matt, it would work; but for how long? That’s usually the question. The battery has a capacity of 18V*5Ah = 90Wh. The flood light draws 60Wh per hour, which means that it will run for 1.5 hours on this battery.

  12. Hello i am thinking about purchasing a 578Wh portable battery to trickle charge my car (battery) when not in use. I’m told that the car utilizes 50mA when parked. How can i calculate how long the portable battery will last?

    • Hello Joe, you have all you need to calculate that, presuming the car battery is 12V. Here’s how you can calculate that: Every hour, your car battery will draw 12V*0.05A=0.6Wh. That’s 0.6Wh per hour. You have a 578Wh battery. You calculate 578Wh/0.6Wh = 963.3 hours; that’s about 40 days (how long will the battery last). Hope this helps.

    • Hello Armando, you’re looking at a 12V battery that runs a 250W device. Here’s how you calculate how many Ah battery you need: 250Wh/12V = 21 Ah. So, you need a 21 Ah 12V battery to run a 250W device for 1 hour.

  13. If i wanted to run 200 watts of led lighting for 12 hours with 12v lithium phosphate deep cycle batteries (in parallel) (solar) how much battery (s)would i require ?

    • Hello Rick, 200W for 12 hours equals 2,400 Wh. That’s your battery capacity. If you want to express this battery capacity is Ah, you have divide 2,400 Wh by 12V; this equals 200 Ah battery. Hope this helps.

  14. If I have appliances and lights that adds up to 904W and I want to use two 6V dry cell batteries and 1 solar panel for 8 hours wat wattage solar panel and what capacity batteries would be required?

    • Hello Michael, here’s how you think about this: To run all the appliances for 1 hour, you would need 904Wh battery capacities. Batteries has a 12V voltage, so that’s 904Wh/12V = 75Ah battery. So, a 75Ah battery should run all these 904W appliances for 1 hour. 150Ah battery would do it for 2 hours, 225Ah for 3 hours, and so on. Of course, if you’re continuously delivering charging the battery via the solar panel, the battery capacity is continuously being replenished. In general, having something like a 200Ah battery is the standard. Hope this gives you some insight.

    • Hell John, well, a 10 amp 12V heater should run on at most 10A×12V = 120W. We could also calculate this for 300W but we need the capacity of the batteries (12V voltage is not sufficient). Do you perhaps have Ah or even Wh labeled on these two batteries? This will help us calculate how long will the batteries be able to run the heater.

  15. You seem like the kinda guy that can finally solve my riddle.
    I have a 12V lead acid battery with 80Ah. I also have an 12V to 240V Inverter that operates at 90% efficiency. I want to run a 60W (240V) pump with that setup. How long will the battery power the pump?

    • Hello John, you can simply this calculation with two things: you have a 60W pump and a battery with 12V*80Ah = 960Wh capacity. You divide the battery capacity by the pump’s wattage like this: 960Wh / 60W = 16h. In short, this battery can power your 60W pump for 16 hours.

  16. Hi! This might be a silly question as I don’t know much about wattage, but I have a 180ah AGM battery, 660 watts of solar, and a 2500 watt inverter, if I ran my hot water heater from the inverter (1440 watts) how long would it take to deplete my battery?
    (Realistically it would only be used for an hour ~ 30 minutes to heat up the water and 20 to use the water) would that work?

    • Hello Courtney, that’s not a silly question at all. The key here is how much energy the battery holds and how much power does hot water heater require. Let’s presume that when running, the hot water heaters runs on 1,440W. This will consume 1,440 Wh every hour. A 180Ah AGM battery has a voltage of 12V; that means it can hold (180Ah*12V = 2,160Wh) 2,160Wh of electricity.

      Now, we divide the battery capacity by per hour usage of the hot water heater like this: 2,160Wh / 1,440Wh = 1.5 hours. That means that you will be able to run (in ideal conditions) your water heater for 1h and 30 minutes before the battery is fully depleted (from 100% to 0%). Hope this makes sense.

  17. Hi LearnMstrics,

    Hope you are doing fine. Anyway, I have a computer mining rig and currently drawing 880w at the wall and powered by a 1200w/240V. My question is, how much battery Ah is needed to power to run 12h? Especially during night time.

    Thank you in advance.

    • Hello Kenny, alright, your rig is drawing 880W. That means that in 12 hours, you are looking at a battery capacity of 880W×12h = 10,560 Wh. If you are using standard 12V batteries, that’s 10,560 Wh/ 12V = 880 Ah battery. Hope this helps.

      • I have just done the calculation with the calculator on this page, 880w with 240v = 3.67 Ah per hour isn’t it?

        So if I wish to power it to run for 12h, which mean the calculation should be 3.67 x 12h = 44.04 ah battery is needed?

        • Hello Kenny, you have to think about the voltage. If you have 240V, you will use 3.67 Ah to get 880W, yes. However, most batteries have 12V voltage. In this case, you will need 880W/12V = 73.3 Ah battery to run it for 1h. For 12 hours, it’s 12 times 73.3 Ah. Hope this makes things a bit clearer.

          • Hello there!

            I am looking to buy an EcoFlow River Pro portable battery station that is 720wh. I want to use it for a dedicated power source for my Starlink that runs around 60w. How long would the portable battery station last running just the Starlink?

          • Hello Jen, you are thinking about this EcoFlow River Pro unit? Yes, this one has a 720Wh battery. Theoretically, your Starlink consumes 60Wh per hour. That means that you could run it for 720Wh/60Wh per hour = 12 hours. If you need more than that, EcoFlow also offers that extra battery for a combined 1,440Wh capacity. That should run the Starlink for 24 hours (a whole day). Hope this makes sense.

      • Hi LearnMetrics,

        I would like to find out the calculation is not correct according to the calculator on this website?

        880w / 240v = 3.52 Ah?

        Thank you

        • Hello Kenny, here is how you calculate the amp-hours: 880W / 240V = 3.67 Ah. The calculator gives this correct result.

  18. Hello,
    I am currently thinking of running my wash room off grid. I have a 2000w washing machine. Would a 12v to 5000w pure sine Inverter working off a 250ah 12v AGM battery which will be attached to solar panels work and wind turbine? Would I need more than one battery?

    • Hello Alyson, this setup will work. Looks like a great setup, actually. If you run the 2000-watt washing machine with a 250Ah 12V AGM battery, you will be able to run it for 1 hour and 30 minutes at 100% output. So, if you need to use it more than 1.5 hours, it would make sense to get additional batteries.

  19. I have a 250 ah 12v battery, I am also using a 2000 watt 120 inverter in my van.

    How many amp hours will a 1200 watt induction cook top use in 1 hour?


    • Hello Susan, alright, a 1,200 Watt induction cooktop will use 1,200 Wh (watt-hours) every hour if you run it at 100% output. The 250Ah 12V battery contains. 250A*12V = 3,000Wh. Theoretically, you could run such a cooktop for 3000Wh per hour / 1200Wh = 2.5 hours. Practically, there are losses when you convert DC to AC, and you will likely be able to run such a cooktop for 2 hours with a 250Ah battery.

      As for amp-hours (be aware that you can’t directly compare Ah from the battery to Ah for the cooktop since they don’t have the same voltage), a 1,200W cooktop on a 120V circuit will run on 10 amps. Therefore your cooktop will use 10Ah per hour on a 120V circuit, if you run it on 100% output. Hope this helps.

  20. Hi

    I have a 320 Watt surround speaker system. My portable power station is 296 Wh (it’s the HP500 Portable Power Station with Lithium Battery).

    It says it’s 80 Ah. I can’t tell if it’s 110 V or something different (instructions give a range of 12 V – 16 V but in DC?? The box says “110V/500W AC Outlet” … is this 110V?). I have found so many different formula to calculate the run time but I figured I’d ask.

    Can this power station power a 320 Watt surround system for at least 3 hours?

    • Hello Hendy, if the power station has 296 Wh capacity, it can run a 320W unit for 296Wh / 320W = 0.925 hours. That’s less than 1 hour. It’s simple watts and hours here; to run it for at least 3 hours you would need about 960Wh battery or power station. Hope this helps.

  21. A lot of this is answering questions I don’t even understand! I want to have (need, in fact) a Mobility Scooter. It is rated at 1000W and has a 60V battery (which may be 5 x 12 – I’ve no way of knowing). I live in a place that has plenty of sunshine all year round (though obviously less hours of it during winter). Could I charge my scooter from Solar panels? There’s no electricity supply anywhere near where I could store the scooter – and I struggle to get about.

    • Hi Elspeth, of course, you can charge a mobility scooter with solar panels. Solar panels usually produce a 12V DC current but you have all kinds of converters that will upgrade the current to 60V. Probably your scooter already has one (or just powers 5 12V batteries, as you have mentioned). Hope this helps.

  22. Hello guys, I’m in a bit of a dilemma,I am planning to get an Xbox series s which is said to run at 90w in full capacity, I’m also planning to get an anker 535(512wh) or 757(1200wh) power stations, I was thinking I’d get at least 512 ÷90 or 1200÷ 90 but apparently the maths isn’t so straight forward because I watched a YouTube video where a guy plugged a 76000mah(250wh) which I thought would give Him about 2 hours of gameplay but he said that since the console is drawing 120v it would give only half an hour, SO MY QUESTION IS DO I NEED AN AMPERE HOUR BATTERY TO GIVE ME UP TO 10 TO 12 HRS OF GAMEPLAY OR STILL USE A WATT HOUR BATTERY AND HOW BIG DOES THE BATTERY HAVE TO BE,THANKS AND GOD BLESS. PS the reason I’m planning to use power stations is because of poor power supply where I live so I want uninterrupted gameplay sessions.

    • Hi Fadil, uninterrupted gameplay is a must! 🙂 To adequately calculate how long will a portable power station last, you have to compare watts (W) and watt-hours (Wh). So, if you have a 90W power draw from the Xbox, you need a 90 Wh battery (with 100% discharge rate) to run it for 1 hour. Now, the YouTube guy: A 250Wh battery with 100% discharge rate should run a 90W device for 2 hours and 47 minutes; it’s just basic math. If the running time was about 2 hours, that means that either the discharge rate was below 100% (72% for example), the power draw was bigger (125W for example) or the battery wasn’t 250Wh. Temperature plays a role for the battery capacity as well.

      In theory, 10h to 12h game time for a 90W device means that you should get 900Wh to 1080Wh portable power station. So, Ankler 535 will not be enough (512 Wh capacity). The Ankler 757 will be enough given the 1200 Wh. Of course, if the discharge rate would be 72% here or Xbox actually draws 125W instead of specified 90W, you will get 9.6 hours (calculated to that YouTube guy metrics). Hope this helps, and good gaming 🙂

      • Thanks for the reply,so the voltage is not an issue? I rewatched the video and I noticed a distinction he made which is the 76,000 mAh powerbank which is capable of delivering 250w of power not 250wh capacity. The battery pack he was using has a 5v and 120v outlet, he said from the 5v outlet one would get 76,000 mAh but for the 120v outlet one would get only about 10,000 mAh,so I was wondering if the voltage would affect the powerstations I’m interested in although their capacity is rated in wh not mAh. Thanks again for your learned response.

  23. Hello, I’ve been fascinated reading all of this! I have a question about inverters and amp hours… I’m looking at getting a 330wh infrared heater.

    I can get one that runs straight off the 12v circuit, and using the calculations, that will get through about 30ah per hour.

    I have an inverter (12v to 230v) that uses I think 2ah per hour.

    If I get the 220w heater to run off the 230v inverter, does that mean that it only consumes 1.43ah per hour (or 3.43ah per hour including the inverter draw) and can therefore run for much longer?

    Or is it just that my 440ah bank (lead acid, so really only 220ah are usable) holds a maximum wattage of 5280wh (of which 2640wh are usable) and so it’s better to run directly off 12v and remove the inverter draw?

    • Hi Lily, now, if you think in volts and amp-hours (Ah), you always have to do a bit more complex calculations. The easiest thing is to just think in watt-hours (Wh); in such a way, you don’t have to worry about 12V, 23V, 2Ah, and so on. Using a 230V inverter, for example, doesn’t increase battery capacity. It will just transform 12V 30Ah current (that’s 330 Wh), to 230V 1.43 Ah (that’s also 330 Wh).
      You have the right idea at the end there; 440Ah power bank holds 2640 Wh of usable electricity (50% discharge rate). You don’t really need an inverter here; just run it off 12V as you have correctly suggested. Hope this helps.

  24. Good day sir. I wanted to say how awesome you are taking the time to help mathematically challenged folks like myself with these calculations. I have tried and failed to properly size a battery bank for my needs. I have a computer system that clocks in at 17.5 kwh per day. I have 1200w of solar panels and a 60amp MPPT charge controller feeding a 3000w pure sine inverter. I currently have a 24w 100ah lifepo4 battery. I would like to get this setup totally off grid. As of now it operates with solar during the day but at night needs ac power. Can you advise me on how many additional batteries I should need to make the rig able to run 24hrs on battery? Thank you!

    • Hi Stephen, alright, let’s look at it like this: 24W 100Ah battery has a 2400 Wh or 2.4 kWh capacity. LifePO4 batteries have a 90% discharge rate, so in practice, this battery can hold up to 2.16 kWh of electricity. To power your 17.5 kWh computer system, you would need 8 of these batteries (8.1, to be exact).

      Now, the reason why your rig operates during the day is because the battery is continuously being charged via solar panels. At night, you don’t get that charge; and even a full battery has only 2.16 kWh capacity. That means it will run a 2160-watt device for only 1 hour.

      Hope all of this makes sense and that you can use it to make adequate calculations.

    • Hi Steven, I’m assuming this is a propane generator? If it is, 3 gallons of propane can theoretically generate 72 kWh of electricity at 100% efficiency. Generators have an about 40% efficiency, so that 3 gallons of propane will generate 28.8 kW or 28,800 watts of electricity. If the light runs on 125W, we divide 28,800W by 125W, and we get the result: 3 gallons of propane in a generator will keep the 125W light running for 230.4 hours. That’s almost 10 days straight. Hope this helps.

  25. Ok! This comment and answer thread is incredible! Thanks for doing all of this. I’m dabbling with the idea of an off grid, indoor grow. I have rounded way up to 500 watts/hour for 18 hours a day. I’m getting 9000wh needed and will be on a 12v battery system. I’m looking at 220ah 12v batteries. At the 90% discharge I’ve gathered that I need 4.17 batteries, correct? If I can nail this down I can move on to a solar/wind hybrid charging system. Thanks for your time.

    • Hi AJ thanks for the comment. Your math is on point quite on point; just needs small changes. Each 220Ah 12V would have a 2,640 Wh total capacity; with a 90% discharge rate, that’s 2,376 Wh of usable juice. You have correctly calculated that you would need 9,000 Wh for 500 watt device to run for 18 hours. If you divide 9,000 Wh by 2,376 Wh, you get 3.79 batteries (220Ah 12V). In short, you need 4 of these batteries to make it work. Congrats on moving to solar/wind, it’s the best green hybrid at the moment.

    • Hi Matt, alright, let’s presume we have a 400Ah 12V battery with 400Ah×12V = 4,800Wh capacity. If the fridge would be running constantly at 50W, it would run for 4,800Wh / 50W = 96 hours before the battery ran out. That’s about 4 days. Hope this gives you an idea on how long you can run your fridge with a 400Ah battery.

  26. PYLE sells a bluetooth speaker they claim has an output of 1000W, but takes a 12 volt lithium battery at 3.6Ah.

    Is the output claim BS? Did they violate the laws thermodynamics?

    • Hi Billy, for 1000W, you would need something like 100V 10A current. 12V and 3.6Ah battery has a capacity of 43.2 Wh. Even at a 100% discharge rate, such a charge can power a 1000W device for about 2 and a half minutes. That’s the math. Nobody can really violate the laws of thermodynamics 🙂

  27. Your doing a fantastic job answering questions. I have a brain fart. Im wiring 3 35ah agm batteries in parallel, so 105ah-12v. If i have a .8amp small fridge, a 40w fan, and a cpap machine ( dont know power) cant be much – how long will, or should be, run? I ran the fan for like 8 hours my first use, did i do damage? Not sure of the 50% rule on agm type batteries. Thank you.

    • Hi Rick, alright, it’s a bit of complex systems, brain fart is natural. The total capacity of 3 35Ah 12V AGM batteries is 105Ah × 12V = 1,260 Wh. If we relly on this Battery University article, the depth of discharge for AGM batteries is 80%. So, the amount of actual juice you have in these 3 batteries is 1,260Wh × 0.8 = 1,008Wh (roughly 1 kWh).

      You ran the 40W fan for 8 hours; that’s 320 Wh, way below what you are allowed to use, you’re safe.
      Now, for all the things that use electricity here: Fan is 40W, small fridges are about 100W (if you have 120V 0.8A fridge, that’s 96W, makes sense), CPAP machine is between 30 and 60 W. So, if you run all 3 units at max. wattage, that would be a maximum of 200 watts. Given that you have a 1 kWh real juice in the batteries, it’s safe to run all 3 of them for 5 hours. Hope this helps.


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