Are there any ways of generating electricity for free*? It doesn't have to be 110/220/230V, but for example charging the mobile would be useful.

* - free in terms of money, e.g. without paying electricity/gas bill for its generation (purchase not included)

  • This question amused and enlightened me, I would say given the best answer, you should change this question to "how to charge my phone for free" :) Commented Mar 13, 2015 at 9:38

6 Answers 6



For this trick, you need an apple!

Charging Phone with a fruit

Just kidding, any acid-like vegetable/fruit is fine:)

In order for a fruit or vegetable be a battery, it needs to be able to conduct electricity (acids make H+ ions/charged particles, when put in a solution like water). These type of acid particles are the same as in electric current. So in other words, more acidic, then better (or more sour it taste, it more acidic). As you can guess, a lemon would make a better battery than banana, however less power than a potato!

To use lemons, for 1.5V you may need around 3-5 lemons connected in series. You can use a copper penny/nail and a galvanized/zinc nail into each side to create +/- terminals). In example:

4 lemon circuit Lemon Circuit - Anode and Cathode

To create fruit-powered Radio Control (RC) Car, you'll need more lemons as shown in the diagram below:

Fruit-powered Radio Control (RC) Car diagram

See this in practice below:

Probably fake, but interesting:

See also:


Power a Nokia phone by giving it some Coke (soda). This invention was done by China-based designer Daizi Zheng who modified mobile device to include a chemical board capable of converting carbohydrates and sugar into energy.

See more: Cell phone powered by Coke makes better use of a sugar rush than you ever will at Digital Trends


Nearly 1 of 10 Americans use smartphones during sex, therefore using body heat can be easily converted into electricity by a new creation from Vodafone. They've developed (something called Power Pocket) which is a thermoelectric material that is small enough to be stitched into clothing and body heat is absorbed by the material and converted into voltage that's able to charge up your device.

Source: Vodafone unveils the future of festival season tech: Charge your phone while you sleep at Vodafone blog


Researchers from England’s University of Bristol and Bristol Robotics Laboratory have found a way to convert your pee into an electrical charge, using bacteria grown on carbon fiber anodes, placed inside ceramic cylinders.



Yelling at a dead phone to charge it? Why not?

Scientists at South Korea’s Sungkyunkwan University found a way to convert a person’s voice into energy.

Source: The phone you can charge with your voice at The Week

A rotary charger

A company based in Mumai called Idea Forge aims to meet the demand for rural cell-phone power with the Roto Charger, a rotary device that works by either cranking the handle (by mimicking a fishing reel) or rolling the device on a surface, then connecting to a cell-phone (one minute of rotation gives around 3 minutes of talk-time).


See: Roto Charger in action (video).

Land line

If you have a land line, you can use it, but it's limited to a few milliamps so it should be enough to charge your mobile phone. See the video.

Please be aware of applicable local/federal laws regarding phone lines in your area.

How to Get Emergency Power from a Phone Line by DIY Hacks and How Tos


See also:

  • 4
    Don't be aware of local laws, be aware of federal laws. When MA bell was queen and the only phone company nation wide, laws were made at a federal level allowing for only phone company authorized devices to be plugged into the phone system.
    – Jon
    Commented Feb 12, 2015 at 22:02
  • 4
    Is the apple still pleasant to eat after it was drained to power a smartphone? If not, then it's not really free, is it? :)
    – gerrit
    Commented Feb 13, 2015 at 15:46
  • @jon so you are saying that every phone set and cables sold at radio shack, best buy, and wal mart have been officially approved by a telecom company?
    – celeriko
    Commented Feb 13, 2015 at 18:17
  • 1
    @celeriko Yes. It's called regulation. Every radio transmitting device is also regulated, whether you believe it or not. If you create a ham radio that is broadcasting too powerful a signal, after some time, someone will knock on your door to shut it off. If you do this, it is very easy to see that you are draining power from the telephone jack without making any calls.
    – Nelson
    Commented Feb 14, 2015 at 6:50
  • @gerrit: Anyway, the actual energy source in an apple / lemon / potato battery is the zinc metal in the nail. Zinc is not free. The fruit just acts as an electrolyte, and is not consumed as fuel (but the dissolved zinc ions do make it taste kind of nasty and metallic, so it's still ruined). Commented Mar 12, 2015 at 19:17

No way to do this without an initial outlay. Either of the following could work:

  • Solar panels
  • Electricity-generating stationary bike
  • A windmill on your roof.
  • 2
    Something to solar panels specifically: There are (as far as I know) two types of solar panels, if you're interested in getting one (small ones; for charging via USB): Monocrystalline and Polycrystalline. Monocrystalline ones are more effective (also work on a more or less cloudy day). Polycrystalline ones are less effective and only work with direct sunlight. Still, it has low amps. I personally use a Monocrystalline together with a power bank, though I never charge my phone directly with the solar panel.
    – Alex
    Commented Feb 13, 2015 at 7:50
  • 8
    Sadly the bike will consume your own energy, and that will show up on the food bill ;)
    – Quentin
    Commented Feb 13, 2015 at 10:39
  • @Quentin The solar panel isn't free either, then. It causes your house to warm up slower, which you will pay off on heating. Commented Feb 13, 2015 at 14:57
  • @JanDvorak If they're on your roof in the winter, yes. But solar panels can also be installed free standing in the middle of a lawn.
    – Mooseman
    Commented Feb 13, 2015 at 15:02
  • @JanDvorak Hmm... Interesting point. I'm now curious what the actual effect there is. I would think that most solar heating of a home comes through the windows rather than onto the roof (especially since roofs are generally insulated pretty well in order to prevent losing heat through them.) Still, a colder upper surface would lead to faster heat transfer away from the roof. I'm also curious what the actual temperature difference is, that is, I'm curious how the reflect/absorb ratio changes with the addition of solar panels. Now I'm going to have to do research. Thanks a lot. - lol
    – reirab
    Commented Feb 13, 2015 at 19:19

If you're like me, then you probably have at least one or two spare electric motors lying around the house. If not, check again: fans, remote-controlled cars, vacuum cleaners, electric lawnmowers, dishwashers, and even electric shavers are all examples of household devices that contain electric motors. (Basically, if it has moving parts, you're probably good to go!)

Why do I bring up the subject of electric motors? Simple!

Any electric motor can also be used as an electric generator.

DISCLAIMER: high-end "brushless" electric motors require special circuitry for use as generators, as do "A/C" motors.

Make sure you know what kind of motor you're dealing with before you start, and ALWAYS do your research! Otherwise, you might end up damaging your electronics (or yourself!) instead of charging them.

Also, ALWAYS make sure to test your rig before you connect anything to it--you might find yourself generating 110V A/C when you expected to find 5V D/C, or vice versa!

If you have any spare electric motors lying around (or are willing to sacrifice an old appliance to get one), then it's just a matter of finding some way to keep the motor spinning, and voila! Free electricity.

Here's few ideas to get you started:

  • Try adding a handle and cranking the motor-generator's shaft manually, or (when you get tired of that) attaching it to a bicycle and pedaling.
  • If you have a decorative windmill in your yard (or can rig one up), that's plenty to turn an appropriately-sized motor-generator. Assuming that you get plenty of wind where you live (this works great in farm country), a setup like this can be scaled all the way from AA-battery charging up to constant 12V power supply.
  • If you live in an apartment and water service is included in your rent, then look up DIY water turbines; it's easier than you'd think (albeit not particularly eco-friendly)!
  • If you have natural flowing water (stream, river) nearby, consider rigging up an old-school water wheel. They can push a lot of torque at a consistent(ly slow) speed, so even some geared motors might be within your reach; appropriately matched to an output, you could potentially get a solid 12-14V D/C out of one of these.
  • If you have one of those novelty hand-crank or shake-to-charge flashlights lying around, they've already done all the work for you; simply tap into the wires that feed its internal battery, and you can extract the power it generates for other purposes.

And while I'm at it, here are a few more best practices to help you make the most of your DIY generator:

  • I highly recommend connecting an appropriately-selected rechargeable battery to the output; as long as you put a diode in line with the wires to make sure that the power flows into the battery instead of out of it (once again, do your research), you can store the electricity you generate for later use!
  • Another option is to add a capacitor in line with the output (note: only works with D/C generators); it will help to smooth out the electricity you produce, so it will play nicer with others.
  • If you're willing to sink an upfront investment into this project, then you can never go wrong with a full-on voltage regulator; these circuits can take any given input voltage (within a certain range), and coerce it to a specific output voltage. If you're planning on directly charging/powering any real electronics with this setup, then one of these is a must!
  • Another fun project (which should only be tackled after you've got a powerful generator pumping a regulated voltage into one or more large 12V batteries) is to invert your D/C power supply so that you can drive 120/240V A/C appliances; this add-on requires that everything up to this point is solid and dependable, but you'll definitely be left with something worth bragging about!

There's enough information to get you going, but as always, do your research! You might be surprised to find how deep this rabbit hole goes. XD

  • 5
    Three problems exist with random electric motors laying around, each significant: how to turn, and how to interface, and stable voltage. Each of these are significant and the answer glibly ignores them. Much innovation and/or engineering is required. If not so it would be easier and fewer people would not be paying the power company. Commented Feb 12, 2015 at 22:56
  • @Daniel: +1 for Combined Humour and Power (CHP) system. (I would have included more links off the bat, but I was still stuck with the 2-links-per-post limit at the time!) Would you object if I cited that link myself? Commented Feb 17, 2015 at 19:30

Yes and no.

Any form of electricity generation can be used for free, if the source of power is free.

So, if you get free gas, a gas generator can be used "for free". If you have free wind or sun, then you can get "free" wind power or solar power.

If you can stick an inductance coil near a power line, you can leech power "for free", at least until you get caught and fined.

If you stick a dynamo on your bicycle, you can generate power "for free" for as long as you pedal. If you live near a stream, or get free water, you can put one wheel in the water, and generate power "for free".

There are a plethora of methods of providing small amounts of electricity to remote villages for lighting.

The big problems with all this are:

  • You're basically converting one form of energy into another, whether it's thermal, kinetic, or whatever. So, you need that form of free energy to convert from.
  • As others have mentioned, there's often an initial outlay to harness/convert the energy.
  • There's often a significant maintenance cost.
  • Once you have the energy, you need to get it to the devices that can use it. Which means laying wires. More cost.
  • Once you have it at the device (whether a mains device, or a battery) you then need to convert it to AC or DC, and step the voltage up or down and clean it to remove spikes and brown-outs and regulate it and smooth it and...
  • There's also the cost of batteries or some other method to store any power you do not use immediately.
  • You need to keep it safe for everyone who might come near it.
  • If you have enough surplus that you want to sell it back to the grid, that's a WHOLE 'nother can of worms!

If you have a chimney you'll also probably have one of those fan on top. They tend to spin quite fast.

You could combine that with a dynamo or better a DC electric motor (dynamo are usually offer more resistance and could stop the fan) to generate power from the wind. Where I'm from is not particularly windy, but the fan is ALWAYS spinning, I guess because of the air flux induced by the chimney.

Then you'll want to plug your home-made-windmill to a battery, so you can use the generated electricity when needed.

Be sure to put a diode in the circuit or you'll end up with the battery powering the motor ;)


Also there is Peltier element (http://en.wikipedia.org/wiki/Thermoelectric_effect) which can be used to convert free "heat" to electricity.

Peltier element allows to convert temperature difference to the voltage and vise versa. You can use any source of heat to produce electricity in that way (fire, sun, hands lots of them). See the video https://www.youtube.com/watch?v=QzTn9GtSpEU

  • Could you add more information on your post as to what this is rather than outsourcing the information to Wikipedia? Would be easier for people to find an answer on this site rather than following a trail of links
    – MrPhooky
    Commented Feb 13, 2015 at 15:49

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