For sure last week was the last heating day of the season, so I’m happy to report a 2nd winter of completely trouble-free geo (see welserver.com/WEL0961/). Total cost was on a par with last year, about 2940 kWh for the season, or $320 at 11 cents/kWh. In October I topped up the flow center with about a quart of water and flipped on the breaker, that was it. I find I don’t even have to bleed the radiators anymore because with the lower geo temperatures, air doesn’t accumulate there. This year we had a couple of consecutive 5°F nights, and we still didn’t need backup heat, although the system did run for 3 hours straight, so that is probably about the limit of cold it will handle. The radiators were topping out at about 118°, with LLT at 125°, which is the recommended max for the unit. One big change was addition of 15 more solar panels in the backyard last June, for a total of 32. The tilt can be adjusted seasonally, using a crank. Fortunately, here in Virginia we can still get straight net metering. We basically break even over summer and fall and go into deficit in the winter, but build up a small surplus in the spring. Overall, we use about 10,000 kWh a year while the panels generate about 7,000 kWh. That includes about 1500 kWh for an electric car and another 1500 kWh for air conditioning with an old 10 SEER air-source unit. I plan to retire next year so driving should be cut by half at least, and planned conversion of the A/C to geo should cut that by at least half as well. So with a little more insulating maybe I can get to zero net usage. But never mind the cost, we love our radiant geo heat. My wife finds the purr of the compressor very soothing, especially compared to the periodic ka-boom of the old oil burner.