Net Zero for 2010 by 73kwh

We made it. We were net positive on our energy use for 2010 by a tiny 73kwh. That's 1.25% (73/5799 kwh used). I guess my engineering work on sizing the solar relative to the geo and general usage was pretty accurate. But maybe it wasn't.

The tweak I made back in Nov raising the geo output temp for the radiant from ~95 degrees to ~105 degrees has initiated big savings. Last winter, we had days when it was cold where the geo ran almost the whole day (both in residence and away). It wasn't because it was struggling to keep up as much as the temp of the water feeding the radiant wasn't high enough to warm the house to the target temp. Thus, the geo kept running as the thermostats were never satisfied. The 95 degrees in the floor was not making our main zone 70 when it was under 20 degrees outside (and wasn't keeping up with 53 when it was below 10 degrees when we were away).

Raising the output temp by 10 degrees raises runtime energy use but only about 10-20% from what I can see. However, its had a dramatic effect on total runtime. The geo can now hit the interior temp even when its below zero (as it was a few days ago) and doesn't run nearly as much. Early signs point to about a 40% energy savings during this Jan compared to last. Projecting that out over the year we'll have upwards of 600-800kwh to spare this year. Looks like just the right amount to power an electric car ;)