In hot water: a quick tip on how you could save power with your dishwasher

We finally have a kitchen after almost 4 months of no cooker and…well not much of anything. Yes, I know you are probably saying, “Here’s a dishwasher tip- don’t get one” or “Get rid of it” but we wanted one and we are pretty stingy with the rest of our power usage. We are currently using under 5kwh per day (average electricity use in Australia is 15kwh per day) and that is with an electric hob and oven (albeit the most efficient electric cooking I could find- we chose electric because gas is terrible for asthmatics like my wife Michelle). If we were using gas (or cooking with wood as we do in winter) our energy use can be as low as 3kwh per day.

When we were looking for  a dishwasher, I was more concerned about energy usage than water usage. The dishwasher we chose uses significantly less water than I was using hand washing and we are able to reuse our water in the garden, but once electricity is gone, it’s gone. We relied on ‘Choice‘ advice for the purchase (you might be surprised how many dishwashers don’t actually clean!). ‘Choice’ is an Australian grass roots consumer group. It is funded by subscription rather than advertising so it does not have any company allegiances and provides excellent impartial reviews and advice on all sorts of products. We ended up deciding on a Bosch “Classic”. It was a balance between water saving, energy saving, function, and price.

When I went to install it, the instructions said not to attach it to the hot water. I was gutted. I had made the assumption that they would just work with hot water like my washing machine. We have free solar hot water and I thought I would be able to take advantage of it. Still, I checked with the plumber and he thought it would be ok to hook it up to the hot tap.

power saving kit

Once it was installed, I borrowed an energy saving kit from my local library and conducted a “highly scientific” experiment to test the difference between running it on hot vs cold water. First, I hooked the dishwasher to the cold tap and ran the fastest cycle. This runs for 30 minutes at 45 degrees Celsius. The energy use was 0.5kwh.

Next, I ran it again using the hot tap and it used 0.3kw. That’s quite a large energy saving. In monetary terms it’s not huge but if you are a solar user it’s a big deal.

twin tap plumbing

If you think you might want to try this yourself, it’s a really easy retrofit for most kitchens with a sink mixer. A new tap (for the wall) can be bought that has 2 outlets on it. The sink mixer goes into one and the dishwasher in the other. Pretty easy fix for a significant energy saving. As always, it’s a good idea to get a professional to help you out.

Important:  my hot water comes through a mixing valve which makes it never hotter that 60 degrees Celsius. If you don’t have mixing valve, your water could be (in the case of solar) close to boiling point. This may destroy your dishwasher and harm your family or at least melt any plastic piping. You have been warned…don’t try this at home without checking first! 😉


About Healthy Harvest Kitchen Gardens

Healthy Harvest provides a permaculture-based kitchen garden service for existing food growers and people who are inspired to grow food. We sell fresh chemical-free seedlings, seeds and seasonal produce. We also provide educational workshops, courses, gardening consultations and services. We can help with new vegetable garden designs, maintenance of established gardens, or converting and improving existing gardens ready for growing food. Please see our website for more information: Check out our blog at for news and interesting bits and pieces.

Posted on November 13, 2012, in Sustainability and tagged , , . Bookmark the permalink. Leave a comment.

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