Whenever I run the dishwasher, the temperature on the thermostat located on the opposite wall goes higher, even though the actual house temperature doesn't. This causes it to run for a lot longer, making the house colder than it normally would get. The wall feels the same as always (not hotter from the dishwasher). I have not the slightest clue why this happens.

My clothes dryer does the same thing to my thermostat. My best suggestion would be to turn the a/c off while the dishwasher is running to avoid an outrageous electric bill :)

Whenever i run the dishwasher, the temperature on the thermostat located on the opposite wall goes higher, even though the actual house temperature doesn't. This causes it to run for a lot longer, making the house colder than it normally would get. The wall feels the same as always (not hotter from the dishwasher). I have not the slightest clue why this happens.
Are you using a heated dry mode on your dishwasher? Even if your not the heat alone from the hot water maybe going up along the ceiling and to your thermostat. It only takes one degree to keep your thermostat to turn on the A/C. You may need to raise your A/C setting or introduce a fan to circulate more air.

It may seem like the heat, but it is not. I put two other thermometers there, and they both read the same temp as if it were off, but not the thermostat. One was another thermostat, and one was a mercury one. Weird!!

I doubt it is the ceiling, because the dishwasher is in an area of 7'9" ceiling, while the thermostat is under a 12 foot vaulted ceiling. The heat would not reach there, as the dishwasher is about 6 feet away, separated by a counter and wall.

BTW, the tstat is a RiteTemp C150 or something. Could it be the dishwasher is causing the electrical wire behidn it to heat up or something? This happened with my old tstat as well, and it only seems to affect it when it is plugged in.

I'm not an expert in this type of thing or anything like that, but maybe the wall is absorbing the heat from the dishwasher and that's what's causing the thermostat to go up.

I thought of that reason, but I have felt the wall and it always feels normal, just as if the washer were off. Unless the washer could heat up across the counter, then transmit all the way through the two panels of drywall, it doesn't seem that is likely.