The Home Page for Emporia’s app provides graphical views for current power and historical energy usage. For user convenience and preference, the app users select various unit settings (i.e., Watts, Carbon, Dollars, etc.) and views of time increments (i.e., Now, Minute, 15-minute, etc.). Explaining the units and CO2 emissions that underlay these settings, this post further helps users better understand the math behind the numbers!
But First, Try Emporia’s Software
If you haven’t already done so, please download Emporia’s app on either the App Store or Google Play. Any user can sample a demo version and doing so will enhance your understanding of this post.
All raw data for app graphs derives from measurements made by Vue hardware installed in a user’s home. Although this post seeks explaining units and CO2 emissions to anyone, it applies best to those who already own or intend to purchase appropriate hardware. If you do not yet own a Vue, click here to purchase!
Vue Hardware Measurement
The Vue measures current (aka ‘amperage’) flowing through breaker-box electrical lines. It also measures voltage from the power supply, which can be either an outlet plug or hardwire in the panel.
The Base Unit of Power: Watts
The Vue uses amperage and voltage data to calculate power (in Watts, W). For reference, a single Watt represents a small unit of power; therefore, it is more common at the homeowner level to speak in terms of kiloWatts (kW – or 1,000 Watts).
1 kW = 1,000 W
Power vs. Energy
As indicated above, W and kW are common units of power, which is distinct from energy. To aid understanding, think about power like water flowing from a faucet. If you open the faucet valve only a little, a small flow results. Open the valve all the way to produce maximum flow. Imagine power as the force your thumb would experience if you tried stopping the flow by hand. Of course, you can feel free to try this experiment at home. Just be prepared to clean up if you use your kitchen sink rather than an outdoor spigot!
In contrast, think about energy in terms of the volume (or weight) of water captured in a container under that faucet. Clearly, that volume is determined by the flow rate and the amount of time the faucet is left on. Obviously, a small flow left on for a long time can produce as much volume (or weight) as maximum flow for a short time. Identical with energy, where small power uses over a long time can use as much energy as short bursts at high power. The most common unit of electrical energy is the kilowatt-hour (kWh), making clear the component of time.
|1 kWh =||1,000 Watts of power used for one hour|
|100 Watts of power used for 10 hours|
|10 Watts of power used for 100 hours|
Power, Energy, and Dollars Viewed in Real Time and in Aggregate
With explaining the basic units of power and energy behind us, we can now look at another setting, Dollars, before proceeding to CO2 emissions.
Starting with the Watt setting, the Now view shows real-time power in W or kW, depending on your current rate of use. Data updates at a rate of once per second with the Vue. Moving to the Minute and 15-Minute views shows average power experienced over those increments. In contrast, once the view pans out to Hour, Day, Week, Month, or Year, it is more convenient to think in terms of energy (kWh). Of interest, this is the unit for which utilities charge for usage. The average charge rate in the US sits at about $0.129 per kWh, but varies by state and utility. Using the appropriate rate for your utility, calculations for the Dollars setting are pretty straightforward.
kWh x price per kWh = cost of energy
The next setting option is Carbon, which for app purposes is shorthand for carbon dioxide, CO2. However, prior to explaining options for expressing the units of CO2 emissions, let’s first examine why carbon is important.
Carbon Dioxide Gas
CO2 is the greenhouse gas most responsible for climate change. It is a natural byproduct of burning plant matter and fossil fuels. The amount of CO2 produced relates directly to the mass and chemical structure of what is burnt. Therefore, we calculate the amount of CO2 sent into the atmosphere using simple conversion factors — just like the charge rate for utility billing. The current conversion factor for grid electricity across the US sits at about 0.4565 kilograms CO2 per kWh (or right at 1.0 pounds CO2 per kWh).
|1 kWh =||0.4565 kg CO2 per kWh|
|1.004 lbs CO2 per kWh|
Fuel to Produce Grid Electricity
We note that the conversion factor sited above is a weighted average across the US. However, we will see that this value can vary greatly depending on how electricity is produced in a given location at a given time.
Grid electricity may be produced from various carbon sources, including coal, natural gas, oil, and woody plant matter. Alternatively, it may derive from non-carbon sources including nuclear, hydro, wind, solar, and geothermal. By region or state, the mix of fuel sources producing electricity causes the average CO2 emission rate to vary widely. It can also change greatly when extra power is required to match demand spikes. For example, the conversion factor may be as low as 0.1345 kg CO2 per kWh for the Upstate NY grid with lots of hydro and nuclear. In contrast, it may be as high as 0.7633 kg CO2 per kWh for parts of the Upper Midwest relying mainly on coal and natural gas.
Carbon Emissions for Our Homes
We now appreciate mass units for CO2 emissions from the grid and can set about explaining their relevance to operating our homes.
To Produce Electricity
At about 1,850 square feet, the average American home uses 11,764 kWh of electricity per year. Consequently, the average home emits about 5,370 kg CO2 per year. However, this number increases in proportion to square footage. In other words, at 2,500 square feet, the average new home is about 35% larger than the average of all homes in the US. Therefore, it emits 7,250 kg CO2 per year.
For the average US home:
|11,764 kWh/yr x 0.4565 kg CO2/kWh=||5,370 kg CO2/yr|
|5.37 metric tonnes CO2 per year|
|11,814 pounds CO2 per year|
|5.91 US tons CO2 per year|
But for the average new US home:
|5,370 kg CO2/yr x 135% =||7,250 kg CO2/yr|
|7.250 metric tonnes CO2 per year|
|15,950 pounds CO2 per year|
|7.98 US tons CO2 per year|
To Produce Heat
In addition to using electrical power, many homes require heating. Most typically, heat derives from burning natural gas, propane, or heating oil. Nevertheless, electrical heating is also common.
Those of us using natural gas or propane tend to produce just over 4.1 metric tonnes of CO2 per year. In a similar manner, those relying on heating oil release just over 5.0 metric tonnes of CO2 per year. Given that new homes tend to be larger than existing houses, we choose to use the larger value for the purposes of the rest of this article. As a result, the average US home produces on the order of 5.0 metric tonnes of CO2 per year for heating. Clearly, not every home will require this level of heating (see: A Note on Numbers below).
Other Ways of Explaining Units and CO2 Emissions
Gallons of Gasoline and Miles Driven
No surprise at this point, but it is also possible to use conversion factors to put energy use in other terms. Just as we succeeded in explaining CO2 emissions units for electricity and heating, so too can we develop other units. For example: gallons of gasoline or miles driven in a car. Again, the math is straightforward using the following conversion factors:
- 8.887 kg CO2 per gallon of gasoline
- 0.404 kg CO2 per mile driven (by an “average” car at 22.0 miles/gallon)
So far, we have addressed only the amount of carbon released to the atmosphere through burning. However, it is also possible to store carbon. After all, that is how carbon finds itself in plant matter and fossil fuels in the first place! In short, plants use CO2 as a building block for growth. And ultimately by eating plants, animals do as well. As a result, CO2 is pulled from the atmosphere to become part of any living thing. This statement applies to everything from bacteria in the soil to plants growing in that soil. Of these plants, trees are the most visible – and perhaps the most effective – living things for long-term storage of carbon.
For this reason, Emporia’s app also provides a Trees setting to view usage in terms of an “average” 10-year-old urban tree. That is to say, this setting corresponds to the amount of CO2 contained in a 10-year-old tree. Of note, this is not a “real” tree, but rather a mathematical composite of common leafy and evergreen varieties.
Again, with appropriate conversion factors, the math is relatively simple:
- 1 average urban tree = 60.6 kg CO2
- 1 average urban tree = 133 pounds CO2
Impact of the Average US Home
As we have seen, the average US home (at 1,850 square feet) releases about 10.4 metric tonnes CO2 per year. Of this, about 5.4 metric tonnes derives from electricity and another 5.0 metric tonnes from heating. Using the conversion factors above, we calculate that this equates to 172 average urban trees per year. We can further calculate that for every 133 kWh we consume in electricity, we on average release the equivalent of one tree’s worth of carbon to the atmosphere. By this math, the average US home releases carbon equivalent to 7.4 trees per month in electricity — and another 7 through heating.
In addition to the trees of carbon we emit for electricity and heat, we also release CO2 through other activities. We have already seen the relationship for driving our cars. But what about our airplane travel? The food we eat? Or the products we purchase? Each of these behaviors comes with its own impact with respect to climate change. Often, these activities will double our annual CO2 output — to 20 metric tonnes CO2 per year or more!
Offsetting Impact with Carbon Credits
Recall the two-way conversion of plant matter to CO2 and CO2 to plant matter. Given that relationship, we can easily use the Emporia app to put our own energy consumption in terms of trees burnt. This provides a strong image for the impact of our energy decisions at home. Most of us will find that image alarming.
However, Emporia offers a method to reduce or even to offset completely this impact! By purchasing certified carbon credits, you can help reduce your net carbon footprint. At a minimum, you may wish to use your Vue to track the credits needed to offset your electricity footprint. Next, you may choose to offset your heating impact. Then you could chip away at other elements: car miles, flight miles, food, or an average basket of consumer products. Finally, the most motivated among us may even consider not just this and future years of impact, but those years that came before. Or perhaps decades — or even a lifetime!
Regardless, Emporia makes purchasing certified carbon credits easy and convenient. Further, you may be surprised to learn how affordable it is to reduce your impact. Click here to learn more about certified carbon credits. Or proceed directly to offsetting your own carbon emissions by clicking here.
A Note on Numbers
Individuals Can Get Lost
Admittedly, this post presents a fair amount of math as well as example calculations. Many of these examples use more than a few decimal places for conversion factors, power, or energy. This level of detail may imply more precision than is valid. So be aware.
As cited throughout this post, these values come from reliable third-party studies. However, we should also acknowledge that the studies look at large and complex data sets. Therefore, a phrase comes to mind regarding statistics, the field used to examine large data sets. Specifically, “it is great for populations, but really poor for individuals.” In other words, the results of large studies can net really good information: for the large group and at the high level.
However, using those numbers to apply to each individual in the group will likely lead to large errors. Few of us are average — and most of us will only approximate average behavior. Think about the “average” tree described above. No real tree is part deciduous and part coniferous! Nevertheless, it is helpful to imagine — and to calculate — what that tree could look like when thinking of a large population of trees. The same goes for humans.
So Find Your Place in the Crowd in Three Easy Steps
Consequently, the numbers derived from large-scale studies can yield plenty of good information to guide our behavior. Further, tools such as Emporia’s Vue platform can provide the insight to translate large study results into terms in scale with individual impact. For this reason, Emporia puts great stock into customizing its app experience for unique users and households. Take advantage of Emporia’s ability to deliver bespoke data in three easy steps.
Step 1: Try Emporia’s Software
Download Emporia’s app on either the App Store or Google Play. Any user can sample a demo version of this app and provide feedback. But the app becomes so much more powerful when installed with Vue hardware! So be sure to complete the second step below, either before or after downloading the Emporia app.
Step 2: Purchase Emporia Vue Hardware
Installed behind your home’s main breaker panel, the Vue works in any market. Though homeowners can often complete this installation in 15-20 minutes, Emporia nonetheless recommends hiring a qualified electrician. However, as a reward for installation, the Vue provides highly granular data and the ability to monitor individual circuits.
Click here to choose your Vue!
Step 3: Reap the Rewards of Success
Simply put, Emporia seeks to put consumers in control of their energy data. By viewing this data in real time, consumers can expect to save between 3% and 13% through awareness and simple conservation. However, Emporia has established the bold goal of saving consumers up to 50% on energy spending over time. Consumers will achieve this level of savings through a combination of app-recommended strategies that will compound over time. Better yet, these opportunities for savings will only increase as utilities proceed further into the renewable-energy transition.