My entire sense of carbon footprint reduction has been radically reshaped.

Our AC at home died this week (not fixable, we’re in for a whole new system).  So we were considering upgrading to a geothermal heat pump.  It’s more expensive, but it’s also more efficient.  I worked out roughly what the break-even point is, and i’s very roughly 25 years in our situation (your mileage may vary) versus buying a new regular heat pump (after the federal subsidy).  This means that getting the system amounts to a 4% investment of funds over what we would pay anyway, which is enough to make it about financially neutral if you have the funds on hand.

But what about carbon?  We are the sort that are willing to spend extra to reduce our footprint, both because it is important and because we want to support the green industries, many of which still have economies of scale to realize.

I looked up our mix of power sources here (relevant number: 69% coal, 26% nuclear) and the carbon footprints associated with various sources of electricity here (relevant numbers: coal: 65 tons of carbon / GBTU, gas: 15 tons /GBTU, wind 0.37 tons /GBTU).

Note the factor between coal and wind:  it’s a factor of 175.  With our actual mix of sources, the exact number is more like 100.  I assume the reason wind is not zero fossil carbon is because the installation and maintenance of wind power equipment require things that run on gasoline and non-wind electric.

We found that for about $500/year, we could switch our electric to 100% wind power.  Of course, at any moment the electricity we get came from a mix of sources, but economically speaking at 100% wind we can be sure that, to a good approximation, the total output of coal plants was not marginally effected by our energy usage, and that the wind generation plants did put 100% of our use onto the grid, at some point.

Roughly speaking, this would save about 5 Mg (megagrams) of carbon, bringing us down to 50 kg  of carbon.

Switching to a geothermal heat pump would be financially neutral, but if we financed it at 4% (ballpark) it would cost about the same, roughly $500/monthyear, and improve our heating, cooling, and water heating efficiencies by about 50%.  If our carbon footprint with wind is about 50 kg, this saves about 7.5 kg of carbon per year (since only some of our electric use would be affected).

Two investments: geothermal heat pump, or switching to wind energy,  5000 kg of carbon per year versus 7.5 kg of carbon per year.

I think lots of people would feel virtuous getting a geothermal heat pump, but if they aren’t also on 100% wind energy then they are really misappropriating their resources to the tune of at least 100:1.  And by “they” I mean “we”;  I’m chagrinned that we just today switched to wind.

If you live in PA go here to switch your power;  otherwise call your provider. 

An interesting twist:  if you are on wind energy, your carbon footprint is so small as to be negligible compared to, say, trips to the grocery store.  This totally changes my attitude about energy use and flips my sense of global stewardship on its head:  to what degree is the tiny carbon footprint of wind turbines offset by the support of the industry and the economies of scale you introduce by buying more wind energy?   Does it even make sense to buy LED bulbs any more?  To have a programmable thermostat?   Shouldn’t we now go buy an electric car?