How to run a washing machine/dishwasher on solar

You may have seen our larger kits listing a washing machine or dishwasher in the What Can This Kit Run? section - much like with running anything on solar, there's a couple things to keep in mind to make this more efficient. 

Washing Machines

Most modern washing machines these days are already very energy efficient, but there are a few things to consider to make the right choice for your off-grid solar system.

A machine with both hot and cold water connections is best, rather than units that heat the water. Heating water with electricity from solar is inefficient, and you likely already have an alternate method used for your other hot water needs that you can plumb in. If you are unable to connect your hot water, use the cold wash settings, especially in winter. 

Looking at most modern washing machines, they typically use only 50-150Wh per load, however they will still require a larger inverter at times. This is because they require a higher wattage (eg 1200W) for a few minutes to run spin-dry mode, and a larger inverter accommodates both this power surge and the continued running of other electronics (fridge, lights, etc) without the interruption of an overload cut-off. Some models use DC motors with soft starts, which have a lower surge. Full loads require higher start up currents, so it may be best to run smaller loads for a more efficient cycle. 

Keep in mind that with the efficiency of modern electronics also comes a more complex system that requires cleaner energy. This is no problem with one of our kits, as they use a pure sine wave inverter, however cheaper inverters and generators put out a modified sine wave which runs a small risk of damaging your appliance if it doesn't have a robust power supply. 

Some examples of power use in popular models:

• Fisher & Paykel Smart Drive Excellence 7.5kg - 80Wh per small load, 140Wh per full load.
• LG 5kg Fuzzy Logic WF-T502TH - 36Wh per small load and 54 Wh per large load. 
• Fisher & Paykel Smart Drive 600 Series - 107 Wh/load.
• Hoover Gemini 4kg - 110Wh/load
• Hitachi 5kg (10-year-old model) - 50Wh/load
• Asko (6 year old front loader) - 90Wh per 'short' cycle.
• 7kg Electrolux Ecovalve - 114Wh on the cold wash cycle & 360Wh with the temperature set at 60 degrees. 

All these models average 85Wh/load.

For help when you're looking at a model to purchase, they energy start rating gives a good average. Read carefully, but for most models they give you the yearly warm wash power use, based on running it once every day. Take this number and divide by 365 to get the daily power use figure. For example, a unit with a 2 star rating using 426kWh per year would use 1.1kWh per use. A similar sized 5 star unit using 180kWh per year would use 0.5kWh per use.

For reference, one 390W solar panel produces 390W per hour. To power a machine that requires 0.5kWh (500Wh) per cycle, you would need sun on that solar panel for 1.3 hours, or 2.8 hours for the 1.1kWh cycle machine.

Dishwashers

Dishwashers are a little more power-hungry than washing machines, due to the water heating required for them to run. 

When picking a washing machine, look out for one that allows you to connect a hot water supply, as some are designed only for cold water. Using pre-heated water will significantly reduce the power needed to run a load, rather than using the internal heater with cold water.

Also, look for a machine that doesn't have a heat drying cycle - hot air is pushed into the machine to turn the moisture into steam, which uses much more energy. Luckily it's being phased out in favour of an air/condensation dry cycle, which simply uses a hot rinse to warm the dishes and causes water to condense on the colder steel body instead.

To run your dishwasher efficiently, we recommend only running it when it's full (without overloading), and to use Eco or Light programmes where possible. For example, here's a table breaking down the power and water usage on various cycles on a machine with hot or cold water supply.

And here's a table breaking down the power and water usage on various cycles on a machine with cold water supply only.

For help when you're looking at a model to purchase, they energy start rating gives a good average. Read carefully, but for most models they give you the yearly cold connection usage, based on running an Eco cycle once every day. Take this number and divide by 365 to get the daily power use figure. For example, a unit with a 2 star rating using 352kWh per year would use 0.9kWh per use. A similar sized 5 star unit using 186kWh per year would use 0.5kWh per use.

For reference, one 390W solar panel produces 390W per hour. To power a machine that requires 0.5kWh (500Wh) per cycle, you would need sun on that solar panel for 1.3 hours, or 2.3 hours for the 1.1kWh cycle machine.

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In the case of both machines, the biggest improvement to energy efficiency comes from having a hot water connection, to allow you to use water heated without electricity, rather than relying on the machine's heater. Our kits are spec'd on middle of the road machines, so a particularly energy efficient model will allow you greater freedom with power use. As always, because these can be higher draw items, always keep in mind how much power you have available and the weather in the coming days before running them. Better to wash your dishes by hand than run out of power!