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When the topic of energy intensive appliances comes up, the dishwasher is rarely mentioned. But this appliance can use a lot of watts too, so make sure your solar panels can supply the power in case you decide to use it.
The average dishwasher uses 1200 to 1800 watts an hour, so it will take 7 x 300 watt solar panels to run. If you use the dishwasher heating option, you will need 3000 watts of solar power.
Calculate Dishwasher Solar Power Needs
Dishwasher power consumption ranges from 1200 watts on the low end to 2400 watts on the high. A typical dishwasher might use 1500 watts, but usage varies per household.
To find out how many solar panels you need:
Dishwasher watts x number of cycles = solar panel watts needed
The average household runs five dishwasher cycles a week. Each cycle can run from one to four hours depending on the settings you chose.
The following examples are for a 1500 watt dishwasher running at normal or typical settings.
You need 1500 watts of solar power to run one dishwasher cycle for an hour. If you use the dry heat option, this could double the power consumption to 3000 watts.
A 5 x 300W solar array can produce 1500 watts an hour in ideal conditions. If it is just one 60 minute cycle, this array can handle it. Our choice in this case would be five sets of the DOKIO 300W Solar Panel Kit.
However some dishwasher cycles can take up to four hours. If each cycle consumes 1500 watts, the solar panels can keep it running as long as there is sunlight available.
Most people do not use their dishwashers daily. Assuming five cycles is the average, you can run it five days a week or every other day. How you run the dishwasher will determine how much solar power is needed.
If you are wondering about running and starting watts, in most models it s the same. A dishwasher that uses 1500 watts to run also consumes 1500 watts to start up.
Why are My Solar Panels Not Running the Dishwasher?
So you installed a 5 x 300 watt solar array to run a 1500 watt dishwasher. Everything was running smoothly but now the appliance will not start. What could be wrong?
The most likely reasons are there is not enough sunlight reaching the solar panels. There could also be problems with the inverter or other system components, including the dishwasher.
The most common reason is the solar panels are not producing enough power. A 5 x 300W solar array can generate 1500 watts an hour, enough for the dishwasher in our example.
But this is presuming there is enough sunlight available. Under ideal conditions, a 300 watt PV module can give you 300 watts an hour. With five of those you get 1500 watts.
But there are many factors that can reduce solar power output such as shading, incorrect installation, cloudy skies etc. Or it could be your solar panels just need some cleaning. You can do this yourself or contact a professional solar cleaning service.
Even if the array is correctly oriented and installed, it might reach 300 watts only for a couple of hours, during noon.
If you wash the dishes during this time, it will run. But if it is early morning the array might not have enough power available.
This is why we recommend installing 7 x 300W solar panels instead of 6 for a 1500 watt dishwasher. More panels means more solar energy can be converted into direct current.
Of course it all boils down to how many sun hours are available. During summer days you can expect at least 5 hours, maybe up to 8 in certain areas. Running any solar powered appliance will be easy.
On the other hand, output will drop significantly during winter. You can have a large solar array up on your roof, but without the sun it won’t produce power.
Do You Need an Inverter to Run Solar Powered Dishwashers?
Virtually all dishwashers run on alternating current (AC). Solar power produces direct current (DC), so an inverter is required to turn DC into AC.
A 1500 watt dishwasher needs a 2000 watt inverter. On paper a 1500 watt inverter is an exact match, but due to inefficiency the system will need more power.
If you just want a recommendation, go with the Renogy 2000W Pure Sine Wave Inverter. For the calculations ,read on.
Inverter efficiency ratings are usually from 85% to 95%. This has a significant effect on watts usage.
For example, a 1500 watt dishwasher on an 85% rated 1500 watt inverter uses 1725 watts.
1500 x 115% = 1725
There is no 1725 watt inverter, the closest size available is 2000 watts.
Now if you run the same dishwasher through a 93% rated inverter the wattage is 1605 watts.
1500 x 107% = 1605
This is applicable not just for dishwashers but other appliances too. And this also shows why high conversion efficiency ratings matter.
Which brings us to the subject of pure sine and modified sine wave inverters. Most appliances run better on pure sine wave. Sensitive devices and power tools for instance, should only use pure sine wave.
With appliances it is more of a case to case basis. Some dishwashers only work with pure sine, but others accept modified sine wave inverters.
The best way to find out is to get in touch with the inverter or appliance manufacturer. They can tell you if the appliance can run on modified sine wave or if it requires pure sine.
Do You Need Batteries to Run Solar Powered Dishwashers?
An off grid home needs a battery bank or a solar generator to run appliances. Solar panels can run virtually any appliance, but there needs to be another power source when the sun sets.
A 1500 watt dishwasher running on a two hour cycle needs a 250ah 12V battery. The battery will be 100% empty by the end of the dishwasher cycle. Increase the battery bank to 500ah if you do not want the depth of discharge (DOD) to drop under 50%.
You can use gel, AGM or lithium batteries. Lithium offers the best DOD rate but costs more. It really depends on how you run the dishwasher, whether it is off the batteries or solar panels.
You do not have to choose one or the other. You can connect the batteries to the solar panel for instance. The solar panels (or array) will charge the battery bank, and you can use the batteries to power the dishwasher. As long as the solar panel is charging, the battery will not lose power.
Another benefit of having a battery bank is you can store unused solar energy into it. This way you can tap into this during low solar power days.
If your home is connected to the power company grid, batteries are not required. You can access AC power anytime and extra power produced by your solar system goes into the utility grid. You can access this anytime too.
How to Reduce Dishwasher Power Consumption
Dishwasher power consumption has gone down, but there are ways to save even more energy.
- Look for the most energy efficient dishwasher. There are a growing number of Energy Star dishwashers available. Their power consumption is lower than typical dishwashers, so they might be worth checking out.
- Set the dishwasher settings to as low as possible.
- Do not use the heat dry option. Let your dishes air dry. The energy savings will be substantial.
- Reduce the number of cycles used. Keep the number to five cycles maximum. If you can lower this, that is even better.
- Set the dishwasher to energy saving mode or economy mode.
- Only use the dishwasher when it is full. Running a half empty dishwasher is going to waste a lot of energy.
- Avoid pre-rinsing to save on power use. Just remove large pieces of leftover food to make cleaning easier and faster.
- And if it is possible, hand wash the dishes.
The great thing about modern dishwashers – and modern appliances in general – is they are more energy efficient than ever. Combined with more efficient solar panels, and you should have no issues keeping dishes clean.