The easiest way to calculate the carbon footprint of your home

It is easy to calculate the carbon footprint of your home. You can calculate your carbon footprint from your heating and electricity bills. Just find the most recent ones and follow the guidance in this article. All the conversion factors are in a table at the end of this article.

For electricity, the bills usually have the full last year of energy use. The energy in electricity is measured in kilowatt-hours (kWh). Each kilowatt-hour of electricity you use that is generated by a power station costs you between 15-23c depending on where you live. Rooftop solar panels (after the subsidies and tax credits) can generate power from your roof at between 3c and 9c per kilowatt-hour, see hereso it is much cheaper to generate your own electricity than to buy it from a utility. Using one kilowatt-hour of electricity causes, on average, about 1 pound of carbon dioxide to be emitted by a power station. Generating electricity from solar panels emits zero carbon dioxide, see here. The carbon footprint of electricity varies from about 0 pounds of carbon dioxide per kilowatt-hour if the electricity is generated by hydropower to about 2 pounds per kilowatt-hour at coal-fired power stations. So just take the number of kilowatt-hours of electricity on your bill for the last year and it is roughly equal to the number of pounds of carbon dioxide emitted.

Heating oil and propane are usually reported in gallons delivered rather than gallons used but if you take what is delivered over a full year it will be pretty close to actual use. If the full year’s delivery is not written on the bill just call your delivery company and ask for the last full year’s deliveries. Burning heating oil emits about 24 pounds of carbon dioxide per gallon so just multiply the number of gallons by 24 to get the pounds of carbon dioxide emitted from heating oil. Propane emit about 13 pounds per gallon so just multiply the gallons delivered in a full year by 13.

Burning natural gas emits about 12 pounds of carbon dioxide per Therm or 120 pounds per million BTUs. BTU is short for British Thermal Unit. A Therm is 100,000 BTUs. Like kilowatt-hours, both are units of energy. So just multiply the number of Therms used by 12 to get the pounds of carbon dioxide emitted from burning natural gas. If your bill is in millions of BTUs (sometimes written MMBTU) then multiply the number of million BTUs used by 120.

You can greatly reduce the carbon footprint caused by heating your house by installing heat pumps to replace, or supplement, your furnace. See here. If you have heat pumps powered by your own solar panels then you can heat your house with a zero-carbon footprint. See here. Heating your house with heat pumps powered by electricity is from solar panels is now the cheapest way to heat your house, even cheaper than heating it with natural gas.

Then just add up the total pounds of carbon dioxide emitted by your house from heating and from electricity. This gives you the total primary carbon footprint of your house in pounds of carbon dioxide. If you prefer to see it in tons, just divide the number of pounds by 2,000. If you came out to somewhere between 5 tons and 50 tons you probably did the calculations correctly.

For example:

If you had 1,000 gallons of heating oil delivered in the last year, which is fairly typical in Massachusetts, then you emitted 1,000 gallons x 24lbs CO2/gallon = 24,000lbs of carbon dioxide from burning heating oil. If you used 1,000 Therms (100 million BTUs) of natural gas, which is also fairly typical in Massachusetts, then you emitted 1,000 Therms x 12lbs CO2/Therm = 12,000lbs of carbon dioxide from burning natural gas. If, in addition, you used 7,000 kilowatt-hours of electricity, again about average in Massachusetts, then you caused about 7,000lbs of carbon dioxide emissions from power stations burning fuels to make the electricity you used. So in the heating oil example your total emission of carbon dioxide was 7,000lbs + 24,000lbs = 31,000lbs (15.5 tons). In the natural gas example it was 7,000lbs + 12,000lbs = 19,000lbs (9.5 tons).

If you found this post helpful you will almost certainly find the book, Zero Carbon Home, even more helpful. It is written in the same easy-to-read style backed by the same rigorous scientific approach and financial analysis. The book costs $20 and is available by clicking here.

Carbon Footprint of Heating Fuels
Pounds of CO2 emittted by burning the following fuels for heating:
Per million BTU’s Per kilowatt-hour Per delivery unit
Natural gas 117 0.40 12 per therm
Heating oil 161 0.55 24 per U.S. gallon
Propane 139 0.47 13 per U.S. gallon
Coal (average) 216 0.74 6002 per ton
Note: Kilowatt-hours, BTUs and therms are all units of energy
There are 3412 BTU’s per kilowatt-hour There are 29.3 kWh/therm of natural gas
There are 293 kilowatt-hours per million BTU’s There are 43.9 kWh/gallon of heating oil
There are 0.0034 million BTU’s per kilowatt-hour There are 26.8 kWh/gallon of propane
There are 29.3 kilowatt-hours per therm There are 8141 kWh/ton of coal
There are 100,000 BTUs per therm
To convert pounds to kilograms divide by 2.2
To convert pounds to tons divide by 2000
Carbon dioxide per million BTUs from US EIA 2018
https://www.eia.gov/environment/emissions/co2_vol_mass.php
Conversions from:
https://www.convertunits.com
http://www.kylesconverter.com
Energy per delivery unit from Google

 

 

 

 

 

How much money did we save and how much carbon dioxide did we cut?

A Summary Of:

Money Saved, Carbon Dioxide Cut, 

Investment and Financial Return.

In addition, the DOE estimates our house value has increased $111,000.

Please note that for triple-glazed windows the investment and savings are the additional costs and savings above that for double-glazed equivalents. Please see Chapter 4 in Zero Carbon Home for details.

If you found this post helpful you will almost certainly find the book, Zero Carbon Home, even more helpful. It is written in the same easy-to-read style backed by the same rigorous scientific approach and financial analysis. The book costs $20 and is available by clicking here.

What is Passivhaus? Should I make my house a passive house?

PassivHaus (Passivehouse), PHIUS

PassivHaus is a standard for low-energy or zero-energy houses. It was developed in Germany by the PassivHaus Institute. There is a U.S. branch of the PassivHaus Institute called the Passive House Institute US or PHIUS. PassivHaus certification requires compliance to their exacting standards for both building materials and methods of construction as well as the final result in terms of energy efficiency. Every element of the construction must be audited back to its source. The PassivHaus standard for total energy use is 60 kilowatt-hours per square meter of floor space per year. This is equal to 5.6 kWh per square foot per year. If your house has 2,500 square feet of living space then your total energy budget to meet the PassivHaus standard (including heating fuel like natural gas or heating oil, plus your electricity use) is about 14,000kWh per year. The average U.S. house uses about 11,000kWh per year in electricity alone. When you add in the extra energy used to heat the home, often five times the amount of energy used in electricity, the average U.S. house uses about 500% more energy than the PassivHaus standard.

After we installed the fab four (insulation, heat pumps, solar panels and triple-glazed windows) our house is using about 6.5 kWh per square foot per year or only about 16% more than the PassivHaus standard. This is a remarkable result given that the Passivhaus standard was created for new houses and our house is a 1970’s design with no sealing of the walls against air infiltration and with only average insulation in the walls. Zero Carbon Home and PassivHaus have similar approaches to reducing energy consumption such as better insulation, low-E triple-glazed windows, heat pumps and solar panels. But because of the prescriptive details and audit trail on building components required by PassivHaus it is almost impossible to apply it to the renovation of an existing house and it is only applicable to new construction. It is both expensive and time consuming to do the audit.

If you found this page intriguing you will almost certainly find the book, Zero Carbon Home,  helpful. It is written in an easy-to-read style backed by a rigorous scientific approach and detailed financial analysis. The book costs $20 and is available by clicking here.

Is a zero carbon home the same as a net zero energy home?

Zero carbon footprint and net zero energy

The terms zero-carbon footprint and net-zero energy mean essentially the same thing. Since even a single light bulb uses electricity (which is a form of energy) a house can never use zero energy. However, since you can generate electricity from solar panels it is possible to have a house that generates all of the energy it uses over the course of a year. If you generate enough energy to power your home every single day of the year then you have gone “off grid”. If you generate as much energy as your house uses over the course of a full year, but not every day, then you have a net-zero energy house which, unless you are able to read in the dark, will require a connection to the grid via a net meter so you have power, and light to read by, at night.  If the energy used by the house is all generated by zero-carbon sources (such as solar panels or a wind turbine) then the terms net-zero energy and zero-carbon footprint mean the same thing. In theory, if you used a diesel-powered generator to make all the electricity your house used (and that was all the energy your house used) then you would have a net-zero energy house, but this is not usually how the term is used. In common usage a net-zero energy house means a house which generates all its energy on site and that energy is made from zero-carbon sources like solar panels or wind turbines. Hence it is equivalent to a zero carbon house.

To see an explanation of other energy and zero-carbon terms click here:

If you found this page interesting you will almost certainly find the book, Zero Carbon Home, helpful. It is written in the same easy-to-read style backed by the same rigorous scientific approach and detailed financial analysis. The book costs $20 and is available by clicking here.