Weekend Heat Experiment

This weekend was the first opportunity (cold enough to warrant heat) to experiment with some strategies to pickup the heat in the house from cold with the least amount of energy used. Fortunately, our geo system was fixed on Friday so we had all resources available. The plan was to turn the geo on and to use the fireplace at the same time for quick pickup. When we got to the house, the indoor temp was 57 and outdoor was in the mid-40s (declining to upper 30s overnight). The geo was started around 4pm and I started the fire around 5pm. I kept the fire at a decent mid burn. We got pick-up of about 4 degrees an hour in the main room (about 35x20 and 12-16 ft ceiling) primarily from the fire. Thus, by 8pm we were in the upper 60s and comfortable.

By that time the geo had the slab warming up (it takes 2-4 hours to heat the concrete slab to noticeably warm from cold). It then heated the bedrooms since the draft warmth from the main room into the bedrooms is only minimal. Those were in the upper 60s by bed time and the fireplace warmth lasted most of the night.

However, the geo did run more then I would have expected overnight. There was one anomaly affecting this as one electronic valve controlling radiant to the basement floor appears to be malfunctioning and always open thus diverting hot water there. However, this longer run most likely due to the main room slab (which is huge) still needing to warm up as the fire pushed the thermostat to stop calling for heat early in the evening. One thing I'll do next time is to not turn the geo on for the main room but just for the bedrooms while I'm heating up with the fire. The main room draws most of the hot water from the geo and thus is not heating the bedrooms optimally. Focusing the heat in the bedrooms will pick them up quickly while the fire warms the main room. I want to see this effect as the one downside is that the main room slab will remain cold (other then right around the fire) and at some point in the night will have to be heated which will be a long cycle. That's inevitable so I'm hoping that the run is only 2-4 hours to warm the slab and pick up the one degree. Geo is much better at maintaining temp then raising it rapidly.

We used about 100kwh total from Friday 4pm-Sunday 2pm. From historical usage, we know that about 30-40kwh was due to non-heating items (cooking, DHW, washing machine, etc.). Thus, 60kwh was for heating. Too high for this temp and time of year. Hoping to keep that around 30kwh.

Summer "Netting"

This summer we netted 2,440kwh of electricity to carry us through the winter heating season. This was 740 hours more than last summer. This was partially due to higher generation this summer (about 220kwh) as July in particular was a banner month vs. a rain filled summer '09. However, the additional 520kwh was purely from conservation.

First, we still had some trailing construction work last summer so usage was higher due to that but it was minimal. It has mostly come from learning about our usage patterns in no small measure from our TED whole house monitoring system. That's really provided deep insight into what appliances use what amount of energy. We've done things like only use one hot water heater in the summer (and probably will continue to into winter except when we have overnight guests) and using our oven more intelligently (cooking items at the same time or consecutively to leverage the previous cooking heat already in the oven).

And so far this fall we haven't had to use the geo heat (and good thing since that's still being repaired). The temps have been warm, we've been getting good passive solar gain, and the fireplace has supplied a nice pick-up for cooler nights. I'm hoping not to have to use regular geo heat until mid-Nov on our way to a net zero year.