Actual Energy Use - 20 Thousand Home Challenge Projects & 20th Project to Meet 1000 Home Challenge

We just approved the 20th Thousand Home Challenge project! Congratulations to Ruth von Goeler and Kelly Slough of Northampton, MA. They participated in National Grid’s Deep Energy Retrofit pilot in 2012. Their OPTION B threshold was 13,071 kWh (OPTION B inputs - fossil fuel heat, 4 in household, 3,208 FFA, and 6,208 HDD (base 65). Andrew Webster of Coldham & Hartman Architects was the project manager.


Their annual energy for the post retrofit monitoring period was 8,136 kWh. Their 110-year-old home was previously insulated and had a relatively efficient heating system. As part of the retrofit they substantially increased the finished floor area and still achieved a 61% reduction in energy use from their baseline. 


Attached is a spreadsheet with data from our twenty completed projects. 


Interesting numbers, ranges, means, and comparisons!  I welcome your observations. What is most interesting from the attached spreadsheet?  Please provide suggestions for charts and graphs to tell the story of the 1000 Home Challenge projects to date.



6.9 kBtu/ Ft2:  Avg Energy Use Index (EUI)[2]; US National avg. 44.8 kBtu/ Ft2 (single family homes)

1.91 kWh/ Ft2: Avg. THC Whole House Energy Use; US National Avg.: 14.27 Ft2

(5) Net Zero or Better

(3) Also charge Electric Vehicles

1,709 kWh/year: Average Energy Use per Occupant

4,554 kWh Average project energy use; 31,389 US National Avg: 31,389 kWh/yr

8,108 kWh Average project Thousand Home Challenge threshold



(17) Homes have PV; (8 of 20) Projects met the Thousand Home Challenge without PV

(93 kW) Total installed PV Capacity (17 homes)



1869 Oldest home; 2008 Newest home

Year Built: (20%) 1850-1899; (25%) 1900-1930; (15%) 1931-1960; (30%) 1961-2000; (10%) 2001-2010

Correlation between indicators of energy performance and age: None

576 Ft2 Smallest home; 3,208 Ft2 Biggest single family home

2,271 Ft2 Average house size (per household)

1.73 Occupants: Average household size

(18) Single-family homes; (2) Duplexes

[1] Energy use is site energy, total household energy; house size is finished floor area (FFA)


[2] This is an average from the 20 projects, not the average energy use for the total square feet of all projects

Tags: 20th, Challenge, Deep, EUI, Energy, Existing, Home, Project, Reductions, Retrofits, More…Thousand, Use

Views: 1278


Replies to This Discussion

I used this as the subject line "Measured Performance - Avg EUI 6.9 KBtu/ft 2 -  Twenty THC Projects - US Avg 44"  of an e-mail to some folks who I thought would be interested in the Home Energy Pros post.

It worked. It got your (and others) attention. 

Regardless of how misguided of a metric it may be, 20 projects with an average EUI of 6.9 kBtu/ft 2 is impressive.   If a person is not familiar with the term, it is still obvious that is is substantially less than 44 kBtu/ft 2 (national SF residential average). 

I think it is important to translate the performance in a wide variety of ways. 


Assuming there is a "best" metric is silo thinking.  It assumes there is one "best" answer.  

I really like how Linda looks at things, she shares what is likely to interest most people, then if you want to slice or dice according to the metric that you find meaningful - go ahead.  

Certainly one might want to look at consumption per occupant, another per sf, maybe another wants to do it by bedroom or get even more granular.  Your objective will define how you want to perform your sort.  

What is pretty clear is we need to move away from picking winners and losers because perspective can make anything a winner, and if there is one way of looking at "best" markets get perverted by that rigidity of thought.

We need to move away from ratings as proxies for energy efficiency, those are obsolete nearly the moment they are defined as the market will evolve beyond them, the average will shift.  Moving to measured energy use is a giant step in the right direction, without it we don't get to the next step of narrowing in on the subset that we are interested in with measuring tape that is meaningful. 

In my mind everything Linda does is moving in the right direction, seeing that only requires not getting stuck in our current schemas.  

RE: Your suggestion re Conveying Carbon Emission Reductions

We have carbon emissions embedded in the Thousand Home Challenge application (based on national averages), so that could be tracked. Even if it is full of assumptions, it would help to convey that projects that meet the THC thresholds achieve a substantial reduction of carbon emissions regardless of the energy sources they choose. 

Here is a comparison of carbon emissions from hypothetical projects. These emissions are calculated from PG&E emission factors. Their electricity is not as carbon intensive as the national average.

Congratulations Linda! 20 projects is really great, and their energy performance is stellar. I assume that since you are sharing this, that the attached data are open for use by others? I've just finished aggregating DER performance across the U.S. from available case studies, and I might want to include these (some already are, of course). As for carbon emissions, I've derived carbon emissions factors for delivered electricity by U.S. state, based upon the US eGRID 2009 data (attached here, in case you're interested). While not exactly up-to-date (i.e., 2013) and not technically perfect in terms of grid structure, these values provide a much more nuanced and valuable metric in terms of carbon emissions, as they may actually direct project teams in different regions to retrofit differently. Anyways, well done on all this! 


Brennan -

Always great to her from you. I would like to learn more about what you have found out from your aggregation of US DER case study performance. If you find projects that appear to meet the 1000 Home Challenge please send them our way. 

The data I posted is public - fine to use or disseminate, though I request that you contact me to make sure that there is no misunderstanding about any of our categories, and that you have the latest version. I am working on an update that I should post within a week.

One of the challenges of posting source energy or carbon emissions is that some of our projects do not have separately metered PV production. They just have net energy use. In some cases it is reported and recorded, but only on an annual basis, and the reporting year may not match our monitoring year. In other cases there was no metering installed to track PV performance. In addition, I have not tracked energy performance by energy source, though we have that data in the project application and actual project documentation. I could flag the projects that are all electric. Even so, not knowing the breakout between PV production, PV exported, electricity consumption from the grid and electricity used from the PV array would render an analysis of carbon emissions inaccurate.


Most of our 1000 home challenge project contacts place a very high value on learning and sharing so they would be open to providing additional info if a 3rd party was interested in digging deeper.

Hello, Brennan!

I am also very interested in what you find from aggregating DER performance across the U.S.  Performance data is going to be key to the general public's evaluation of this level of retrofit.  It is exciting to see such a rapidly growing body of published performance data and analysis!

We (BSC) recently finished a report for Building America that analyzed data from the National Grid DER Pilot Program (2009-2012).   This Pilot yielded 42 DER projects (37 comprehensive retrofits, 5 partial DERs).  As far as energy use, we focused on what the building used.  In other words, we want to know how low the retrofit measures were able to get the energy use and we were not interested in how much any on-site generation facilities produced (not that producing energy on site isn't interesting, but on-site generation is not the same thing as building - and building occupant! -  performance).   As Linda experienced with these THC projects, it was difficult to find the actual use for buildings with PV given that the utility data is, for the most part, net use.  In other cases, the utility data is fraught with apparent attempts to reconcile estimated reads and a hugely changed energy use profile.  Some projects did not have sufficient full occupancy since completing the project.  Some folks just didn't respond to requests (contractual obligations relative to the generous financial incentives from National Grid) for information.  In the end, we were able to get usable post-retrofit energy use data for 29 projects. 

I haven't had a chance to compare these projects in detail to the THC projects (there's a small overlap of projects) except to note that the THC projects kicked rumpus even relative to the amazing National Grid DER projects (it's only partly a difference of comparing gross use to net use)!

The Building America report on the National Grid DER Pilot has been approved for publication but I do not see that it has been posted yet.  The report is titled "Performance Results for Massachusetts & Rhode Island DER Pilot Community".   I know we included tables of data so I think this should provide some projects to add to your aggregation study.



Ken, can you send me a copy of the report ( I would love to review it. I'm not sure I can include the data points in my summary (as we're nearly finished writing the report), though I've already used what was provided in your prior summary of the pilot homes, as well as the 7 Cold climate projects summarized by BSC (can't remember if you're author or not?). I will definitely add your paper as a pre-pub reference, at the very least. Thanks for reaching out and I look forward to hearing from you and learning more about the project. As we get things finalized, I can also send you a copy of our paper.



Brennan, you can find the report here:



Thank you Ken, I'll read this with much interest.


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