A watt is a watt - there is no such thing as "watts per hour", or "watts per day". If something uses watts, that is simply the voltage times the amps. If it draws 10 amps at 12 volts, or 1 amp at volts, it is still watts. A watt is defined as one Joule per second, so saying watts per hour is like saying "miles per hour per day". A watt-hour or kilowatt hour, kWh is simply how many watts times how many hours that is used for. This is what most people mean when they say "watts per day".
If a light uses watts, and it is on for 9 hours, that is watt-hours. When you buy power from your friendly utility look at your last bill , they sell it to you at so much per kWh. A kWh is a "kilowatt-hour", or watts for one hour or 1 watt for hours.
An amp is a measure of electrical current at the moment. Amps do not come in "amps per hour" or "amps per day" either. Amps are important because it determines what wire size you need, especially on the DC low voltage side of an inverter. All wire has resistance, and amps flowing through a wire makes heat. If your wire is too small for the amps, you get hot wires.
You can also get voltage drops in the wire if it is too small. This is not usually a good thing. An amp is defined as 1 Coulomb per second. A Coulomb is the charge of 6. Therefore, 1 Amp is equal to the charge of 6. Amp-hours usually abbreviated as AH are what most people mean when they say "amps per hour" etc. AH are very important, as it is the main measure of battery capacity. Since most inverters run from batteries, the AH capacity determines how long you can run.
See our battery page for much more detailed information. An inverter needs to supply two needs - Peak , or surge power, and the typical or usual power. Inverters come in size ratings all the way from 50 watts up to 50, watts, although units larger than 11, watts are very seldom used in household or other PV systems. For this example, a 4 AWT cable is required to handle watts of startup power. That is huge cable. You may also want to consider an inline fuse.
A amp for this example is perfect. To figure out the size of fuse, you divide your AC watts startup by DC voltage. You would need a amp fuse or bigger. I recommend a amp just in case you were to max out the watt inverter. This is just a brief example. There are many different ways to set up your system. You can use solar panels, wind, etc. So, when asking yourself: What size inverter do I need? Remember that there are multiple factors that affect the necessary wattage.
While the process for calculating this may seem simple enough, you have to consider the surge power in addition to power loss and other details that involve your electronic systems.
Previous Next. What size of inverter do I need? Some common questions include: Can I run a freezer on an inverter? What can I run off a w inverter? What inverter do I need to run a microwave? Some appliances, particularly those with electric motors, need a much higher start up surge than they do when running. Pumps, compressors and air conditioners are the most common example and another common one is freezers and refrigerators compressors.
Typical is what the inverter has to supply on a steady basis. This is the continuous rating. The actual operating power requirement rating is higher than the cooking power rating for example, a microwave with "advertised" rating of W usually corresponds to almost W - W of power consumption.
The actual power consumption is usually stated on a label located at the back of the microwave. If the operating power requirement. A none LED camera flash generally requires a pure sine wave inverter capable of surging to at least four times the Watt Sec rating of the strobe. For instance, a camera flash rated at W requires an inverter capable of W or more.
A laser printer generally requires a pure sine wave inverter capable of producing at least three times the continuous wattage rating of the printer. For instance, a laser printer rated at W requires an inverter rated at W or higher. An inkjet printer does not maintain the same requirements as a laser printer. Although most inverters are shielded and filtered to minimise signal interference, some interfence with your television picture may be unavoidable, especially with weak signals.
Here are some suggestions that may improve reception:. First make sure that the television antenna produces a clear signal under normal operating conditions i. Also ensure that the antenna cable is properly shielded and of good quality. Isolate the television, its power cord and antenna cables from the 12V power source by running an extension cord from the inverter to the TV set. Ensure that any excess AC power cord is a distance away from the TV set. Coil the television power cord and the input cables running from the 12V power source to the inverter.
Attach a "Ferrite Data Line Filter" to the television power cord. More than one filter may be required. NOTE: Some inexpensive audio systems may experience a slight "buzzing" sound when operated with a modified sine wave inverter. This is caused by deficient filters in the audio system. Pure sine wave inverter can be used to reduce the buzzing noise. DO NOT use an inverter to directly recharge nickel-cadmium batteries through appliances. Always use the charger provided with that appliance.
DO NOT plug in battery chargers for cordless power tools if the charger carries a warning that dangerous voltages are present at the battery terminals. Some fluorescent lamps may not be fully compatible with an inverter. If the lamp appears to be too bright, flickering or fails to light up, do not use the lamp with an inverter. Some fans with synchronous motors may slightly increase in speed RPM and increase in noise when powered by an inverter.
Certain chargers for small nickel-cadmium batteries can be damaged if plugged into a modified sine wave inverter. In particular, two types of appliances are susceptible to modified sine wave:. Small, battery-operated appliances such as flashlights, cordless razors and toothbrushes that can be plugged directly into an AC receptacle to recharge.
Certain battery chargers for battery packs that are used in some cordless hand-tools. Chargers for these tools have a warning label stating that dangerous voltages are present at the battery terminals.
DO NOT use modified sine wave inverters with the above two types of equipment. The majority of portable appliances do not have this problem. Most portable appliances use separate transformers or chargers that plug into AC receptacles to supply a low-voltage DC or AC output to the appliance. If the appliance label states that the charger or adaptor produces a low-voltage DC or AC output 30V or less , there should be no problem powering that charger or adaptor. Safety Warning: V of electricity can be lethal.
Improper use of a power inverter will result in property damage, personal injury, or loss of life. Please read and follow carefully the instructions in the instruction manual provided with every inverter for important safety considerations and precautions.
It's best to run battery cables to a dry, cool mounting location. Keep the inverter dry. Do not expose it to rain or moisture. DO NOT operate the inverter if you, the inverter, the device being operated, or any other surfaces that may come in contact with any power source are wet.
Water and many other liquids can conduct electricity which may lead to serious injury or death.
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