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When people talk about appliance power hogs, a refrigerator or air conditioner comes to mind. But a washing machine can also use up a lot of watts and amps. So if you are going to run it off an inverter, what specs will you need to avoid overloading the system?
A 1000 watt pure sine inverter can run a fully loaded 7kg washing machine. But if you use hot water instead of cold, power consumption will go up to 1500 watts and will require a 3000 watt inverter.
Calculate Washing Machine Inverter Requirements
There are different types of washing machines and their usage varies from case to case. If yours differs from the example below, replace the usage hours and watts with your own.
To figure out how much power your washing machine consumes:
Rated watts x hours used + 100% = inverter size
An energy efficient washing machine uses 500 watts an hour on average. If you run it for two hours:
500 watts x 2 hours =1000 watts
1000 watts + 100% = 2000 watts inverter size
If you wash your clothes for an hour, a 1000 watt inverter will be enough. If the machine needs more than 500 watts you can use the same formula, but the inverter size will be larger. For a 1000 watt system, we suggest the BESTEK Pure Sine Wave Inverter.
In most inverter calculations the minimum reserve power is 25% or 50%. But for washing machines it is better to double the capacity to handle sudden power surges.
Doubling the capacity seems like a lot, but the more powerful the appliance, the higher the potential surge. With sensitive appliances and devices you should always have reserve power.
The inverter size given here is only for running a washing machine. A 1000 watt inverter works with a 500 watt system. But if you connect a fan, lights etc. to the inverter, there won’t be enough power to run everything.
How Many Watts Does a Washing Machine Use?
Older washing machines consume a lot of power and are not suitable for solar powered off grid homes. Newer, energy efficient models use 300 to 500 watts on average.
A small, energy efficient washing machine may use only 300 watts an hour. A single solar panel can run it or a small inverter connected to a 100ah battery. On the other hand, older less efficient models use 1500 to 3000 watts. Check the UL label on your washing machine to find out how much power it uses.
The power usage stated on these machines are for average use. The label may state 500 watts because it assumes you will be running the unit for an hour with cold water. If you use hot water to wash clothes for two hours, the usage could triple to 1500 watts or be even higher. From 1000 watts you will need a 3000 watt inverter to wash your clothes.
You can use solar panels to run a washing machine, so there is no reason why you cannot do so with an inverter and batteries. But you have to make sure your system has the right specs.
Before you decide buy an inverter, decide how you will use your washing machine. Buying an energy efficient model is required, but you also have to use it properly so your inverter can run it.
How Long Will My Inverter Run a Washing Machine?
If you are on a grid tied system, the machine can keep running as long as needed. If you are off the grid, it depends on the battery bank size. An inverter with a 150ah battery can run a 500W washing machine for an hour.
If like most homes you are tied to the grid, you have access to electrical power. Whether it is a washing machine, toaster, microwave there is no problem. If there is no solar power, the inverter can run off the grid.
If you are off the grid, the inverter will draw power from the battery. The battery size will depend on three factors: how long you need to wash clothes, its power requirements and what other appliances will be connected to the inverter.
Inverter Battery Size For Washing Machines
Battery capacity is rated in amp hours (ah) so you need to find its watts equivalent first. Assuming you have a 500 watt clothes washer, a 150ah 12V battery will do.
150 ah x 12V = 1800 watts
1800 watts seems too much for a machine that consumes 500 watts an hour. However most solar batteries used are lead acid or FLA which can only be used at half capacity. So while 150ah is 1800 watts, only 900 watts can be used.
900 watts is less than the 1000 watts recommended for an inverter, but it should be fine if used sparingly. But if you wash clothes regularly then get a 200ah battery as it is the next most common size available after 150ah.
Please note that a 1000 watt inverter and 150ah-200ah battery is only for a 500 watt washing machine that uses cold water. Even an energy efficient model will consume a lot of power if you opt for hot water. If you have an old model and run it with hot water, a 3000 watt inverter may be in order.
If you have a lithium battery you can use up to 90% or 100%. So it is possible to connect a 75ah lithium battery to an inverter and run a 300W or 500W washing machine. This will almost drain the battery completely after an hour but it will not cause damage.
For washing machines, a lithium battery is ideal. We recommend the Ampere Time LiFePO4 200ah battery especially if you will use a clothes washer similar to the scenario given here.
How to Reduce Power Consumption of a Washing Machine
The heating component uses the most power in washing machines. This is the part that heats water. If you do not heat water, you can reduce watt usage by up to 70%.
Wash with cold water. Washing machines can be used two ways, with hot water or cold water. Washing with cold water uses less power. It is not true that using cold water will damage clothes. In fact, it may help preserve the color and keep the fabric from fading.
Use an energy efficient model. If you have a relatively new model it is likely Energy Star compliant. If you have an old model, consider replacing it. It is an expense, but you will save money in the long run. A power hog is not good for inverters or batteries of any size.
Soak the stains first. Leave stained clothing in cold water for 30 minutes before putting them in the machine. This lessens the amount of cleaning required. The less work, the less watts consumed. Better yet, use a stain remover.
Use the most efficient cycle. All models have an efficient or economic cycle mode. This can reduce power usage significantly These modes run the shortest cycles and a great option if you want to save on the batteries.
Use solar panels. If you run the washing machine on solar panels, you won’t use up any batteries. Let the machine run off the panels so you can conserve inverter power. If the sun is out, why not save your 1000 watt inverter for other solar appliances and take advantage of free energy?
Turn the machine off. Do not leave the machine in standby mode. That does not turn the unit off and it will still consume power. This is one of the most common explanations for why charge controllers drain batteries, and it could do the same with inverters and batteries. When you are done, turn the machine off and unplug it. Do this for all your appliances and you might be surprised how much energy you save.
Wash at full load. A simple advice but every effective. A washing machine always uses the same amount of energy whether it is full or not. So wait until you have enough clothes to fill the machine. Most of us do not like to wait for dirty clothes to pile up, but it is the best approach in this case.
Just like refrigerators and AC units, going for an energy efficient washing machine is the way to go. By managing how you wash clothes, you can reduce the amount of power used by the appliance and cut on costs.