We basically have free hot water as surplus PV is diverted to a 65l tank. I noticed in the manual for the dishwasher that it can take cold water up to 30C. I had an old shower mixer, so I've shoe horned that into the cold and hot feeds under the sink. Early results show a 25% energy saving - the heating element is normally on 12 mins, and it's on 8 mins.
Before I start planning a cruise with the saved money, it's worth noting that it's 25% of the water heating phase. Why? Because the PV pays for the the period where the pump runs. Our modest PV will never cover the 2kW of the heater. Hover, this is the dominant cost of a dishwasher for most people. Today we are generating say 1kW. The DW heater plus other loads total around 2.1kW, so for a 12 minute period we pay for 1.1kW, or 220Wh. This happens twice for a 'run' so 440Wh. With hot water feed, the heater runs for 8 mins, so the 440W becomes 330Wh. Over a year assuming we run it every day and it's a sunny day that's 40kWh, or around 8€ saved!
There are days when we have little or no PV, but still have hot water from the day before. In that case the savings, assuming 300W PV, on say 1.8kW are 360Wh x 2 = 720Wh * 0.25 * 365 = 66Wh / 13€
I'm not convinced the savings even paid for the PTFE tape and certainly not the 2 hours or so I spent, but it all helps. I'm still trying to find a way to offset the router which takes 20W 24/7 (35€) and push it into the daytime. It takes quite a big battery to run it from say 8pm to 8am.
Some dishwashers, in particular Bosch and Smeg, can take cold water up to 60C which would almost double the savings.
~jan 2023. PSU failed. Threw in an old usb adapter.
12/11/23 Looks like the inlet valve is passing. Came to use the DW and found it had so much water in it, it flowed out when I opened the door. This tripped the flood alarm so I had to take it apart to dry it out. I have noticed increasingly that there is water in there and assumed that it wasnt pumping out correctly.
