Getting off Oil in Damariscotta
When people look for "a list of options" instead of an optimal, system-level energy solution for their houses, it betrays a perspective of buildings as collections of optional parts. If one proposed, as the most economical option, the purchase of your next automobile from NAPA Auto Parts for assembly in the back yard, one would likely be considered a bit of a nut. Yet that is the exact counterpart of looking for the cheapest "parts list" for improving a house. In the real world nothing can be "externalized": everything – gasoline spilled into wetlands, a badly built building – has a price someone will end up paying. Be they due to tradition, misguided economies, or just plain not knowing any better, you will pay for your home’s shortcomings just the same. We either pay what it costs to correct mistakes of the past or stay stuck with them. And the sooner we pay to correct those mistakes, the less being stuck with them will cost.
Every house deserves a thoughtful, comprehensive set of energy solutions. Our early 20th century Damariscotta house, for example, burned 916 gallons of oil plus 2 cords of wood for winter heating at the time of our 2010 energy audit. Since then, with a systemic plan in mind to cut our energy consumption by at least 75% and get off oil, we fabricated and installed double-glazed inside storm panels on all windows, insulated the basement ceiling and did some air sealing around the house. Though last winter was much colder than winter 2010, we only burned the equivalent of 808 gallons of oil, mostly wood pellets in a fireplace insert, cutting our fuel bill by 52%.
But handling 300 40 lb. pellet bags each winter, not to mention frequent cleanups of the stove, is an increasingly daunting prospect for old folks like us. We decided against continuing with the pellet insert and explored converting to a pellet-fired boiler instead. It would feed itself automatically from a bin filled up periodically by a bulk delivery truck. Installed cost came to $15,784, including materials for the support structure of the pellet-silo kit. Neat system, reasonable cost, good match for our hydronic heating system. Unfortunately, we would also have to pay for lining the chimney and removal of the oil fired boiler and tank. Even with a $5,000 rebate, the net cost rose to almost $17,000.
Next we explored geothermal heating. Great concept, combining a high efficiency heat pump with constant ground temperature as its heat source. But the bore hole would have cost more than the heat pump, we would have had to install expensive duct work in virtually every room, and there would have been landscaping costs as well. Total price, including removal of old equipment: $28,583
Today our 4.08kW solar system of sixteen 255 Watt Canadian monosilicon photovoltaic panels delivers up to 600 volts of direct current (depending on sunlight intensity) to a German-made inverter, which converts it to standard 220/240 V 60Hz alternating current, compatible with the public power grid. The inverter is connected to the main power panel of the house through a circuit breaker. The system can be monitored remotely via the Internet, or through a display at the inverter. Power is generated with no moving parts, no noise. There is some power available even when it is raining -- as long as there is daylight. Such systems perform at their peak during the greatest power demand times of summer. This permits us to build up a lot of credit with CMP, to be used during the winter heating season.
Having forsworn oil, we will now heat with a mini-split electric heat-pump (with wood back-up, if needed). The motivation to install this system was simple: we couldn't afford not to do it. According to the latest EIA figures, it costs $37.17 per million Btus to heat with oil, compared with $19.43 with wood pellets and only $14.62 with an air source heat-pump. To comfort-heat our house takes about 140 million Btus of heat per year, i.e. $5,203 with oil, $2,720 with wood pellets, and $2,047 with the heat-pump. Our savings, compared to heating with oil, will be $3,156 per year, not counting any oil price inflation. The installed cost of the heat-pump, less a $500 rebate has been $3,397. The solar PV system is expected to feed into the grid 5,012 kWh of renewably generated electricity per year, resulting in an annual credit of over $800 against our electric bill, increasing annual cost savings to $4,197. The net cost of the solar system, after discounts/tax credits, was $8,584 installed, for a combined total outlay of $11,981. Our system will therefore pay for itself in less than 3 years. Just as important: the PV system alone will reduce our carbon emissions by 4,601 lbs. annually, in addition to the 21,250 lbs. reduction from not burning oil for heating. That's 12.93 tons of carbon dioxide reduction per year.
Additional economies will be realized from yet to be undertaken improvements to the house, reducing the heating load further. I’ll throw in summer cooling as a bonus.