Energy Consumption Comparisons

An energy analysis breaks down usage and its sources—data that can help identify places to make energy upgrades

Part of an energy auditor’s job is energy analysis, which includes historical energy consumption data to determine if usage is as expected. One method is to compare a home’s energy use to some average—the local rural electricity provider I contract with calls this ‘compared to your neighbors’.” This average could be the national average, but it’s better to compare at a more local level, such as by state.

There are a few sources for this information including the U.S. Energy Information Administration – EIA – Independent Statistics and Analysis. This dashboard provides several energy consumption metrics, expressed in MMBtu and kWh, broken down by state; it also displays U.S. national averages. (Sorry, Canadian friends.)

Measuring energy use

Before we dive into the analysis, we should look at the two measurement units used to compare energy usage: Million British Thermal Units (MMBtu) and kilowatt-hours (kWh). One Btu is defined as the amount of energy required to raise the temperature of 1 lb. of water 1 degree; 1 MMBtu equals 1,000,000 Btu.

A watt is a unit of power, one joule (J) per second. As an energy auditor, I look for electricity consumed, which is billed by kWh, or 1000 watts per hour. We can convert kWh to Btu and vice-versa. One kWh equals 3412 Btu; 1 MMBtu is equal to a little more than 293 kWh.

Calculating energy use

Now that we have a basic understanding of the metrics we use for an energy analysis, let’s use the data to perform a basic energy assessment. We’ll use my home as an example (lead image). The house is located in northern Minnesota, Climate Zone 7. It has a conditioned floor area of 2054 sq. ft. It’s primary source of heat is a natural gas forced-air furnace (the only gas-burning appliance). There is also a central ducted…

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1. | | #1

A 35 year old water heater, they don't make them like that anymore !! I always liked to use BTU's per square foot of conditioned space per heating degree day as a measure of energy efficiency. With metered gas a lot of data can be mined from daily, monthly and yearly gas meter readings. Quite easy to flesh out the non-heating portion of gas usage by taking summer readings as well. Btu/sf/hdd is a nice way to track incremental energy improvements for those of us who do a bit at a time. The Btu/sf/hdd measurement is also handy in doing side by side energy use comparison for heating of homes in a neighborhood or city.

Doug

2. | | #2

I always enjoy Randy’s post — he did a great job on reviewing my house plans and offering suggestions!

3. | | #3

For your air source heat pump water heater you might wish to use a split unit that prevents the heat stealing.
https://www.eco2waterheater.com/product-info

4. Expert Member
| | #4

Solid information, as always.

5. | | #5

Randy-
Any experience and thoughts with waste water heat recovery? I have one in my house with gauges and in the winter months when someone is taking a shower it pre-heats the incoming water by 15-20 degrees. Installed it 14 years ago, all copper, cost about \$500 back then, has no moving parts and needs no maintenance.

1. | | #6

Hi Jud,

I am familiar with wastewater heat recovery. Over the years I have worked on a few projects where they were installed. My understanding is that they have a faster payback when used in buildings where a lot of hot water is used, multi-family, laundry facilities, etc... but, if you are constructing a home with the plan of it being around for a century or more, why not.

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