Buy a Nest thermostat to save the planet.

I have a history of turning down the thermostat. In 2009, when I was broke, I started to reduce the heat down below 60 degrees (F) at night. That was our model for years, until last winter, when I got up to go to the bathroom and ended up fainting due to the cold and loss of blood pressure. I got a serious concussion from falling. That is a separate story, but once that happened, the use of my old thermostat model went out the window, and it was set to manual. 

I began this research on the Nest by digging into the decision of whether to upgrade my 20-year old furnace, but I also started to see a $5,000-8,000 price tag pretty quickly to get to 95% efficiency from 80%. My total heating bill is $1,000 a year, so the rough economic and environmental decision on a new furnace, where in theory I could save $200-$300 per year while my current one is working seemed economically suboptimal. My furnace will get upgraded soon, but not until it fails completely, and in the meantime, I am pretty good at fixing things on it. 

Our house is a glass house and is hard to heat, but we don’t live in a place where heating is a daily requirement to keep pipes from freezing more than ten days a year. There are many times when the house is empty during the day but still heated. Now that I understand the fainting risk, I will handle the cold better. 

But I started to look at control systems and how I operate my old furnace, and I ended up modeling the Nest thermostat. 

So the Nest is the second lowest-hanging fruit I can to do at my house: tiny amounts of money spent but a pretty substantial environmental shift. 

I am planning on spending $249, and I will get $50 back in rebates. I expect to reduce my carbon footprint by 20-plus tonnes (assuming I will get A/C, or use the Nest on extreme settings). 

The nIR score of the Nest after the rebate is 11.80 (assuming we have A/C), or we expect for the $199 we spend to get ~$2,337 in environmental and economic returns. 

We don’t have A/C, but the nIR score without it will be similar to what I modeled because I will use it for an extreme reduction in the heat for the day time when no one is home, and more than a few degrees at night after people are asleep. 

What are the drivers? 

• $161 per year reduction in my energy bill
• 2.25 tonnes of CO2 not emitted per year
• And that’s just assuming a 10-year life; my current thermostat is 20 years old. 

That magnitude of the impact is hard to understand, but I want to break it down. What is the scale of this financial impact?

• If I bought a 4% annuity that paid $161 per year for the rest of my life, I would expect to spend $4,025. 
• If an average American wanted to earn $161 after taxes, they would have to work one more full day a year. 

If I wanted to reduce my carbon footprint by 2.25 tonnes per year, my other choices would be:

• Install 3 kW of solar on my roof; ~$9,000 investment
• Sell my Accord and buy a Prius; $6,000 investment (WAG math)
• Drive 7,500 miles a year less; $70,000+ investment, as I could not work (WAG math)
• Install 47 LED light bulbs in my house, $23-70 marginal investment, and already done. 

How does the nIR of the Nest stack up? It is excellent; the only thing a homeowner can buy that has a higher nIR is LED light bulbs. So if you are on a limited budget, first buy LED light bulbs, but the Nest appears to be a solid second place. 

Why can’t I just buy 10 to save the environment? (You can.) I would recommend buying Nest as gifts this Christmas, but the Nest does not remove carbon, or produce 0 emissions. It falls into the category of saving by conservation. It is only the first stage in making a real environmental change. Every HVAC system should have a smart thermostat, and I encourage pushing for 100% rebates for homeowners. 

So if you have $9,000 for solar, go buy 45 nests or 9,000 LED light bulbs and donate them to low-income people in your neighborhood. You will not look as green, but you will do far more for the planet than planting solar on your roof.  

What is coming next in my nIR work? I am working on infographics to tell these stories better. I am also working on modeling utilizing multiple choices, like cars or slurry pumps. The best questions I always get are, “Yes, doing X is better, but is it the best option? And what is the marginal dollar savings of doing X + Y versus just X?” I still can’t answer that question, but I am working on it.