Since September 2021, the automated monthly reports we send to our clients summarizing their portfolios’ energy savings have contained a footnote that normally reads something like this one:

Greenhouse gas (GHG) emissions measured at hourly intervals throughout the month were 641,161 kg CO2-eq; 126,132 kg (16%) lower than the estimates generated by using official (static) greenhouse gas emissions factors.

At first this was an academic exercise. We were interested to see whether the rapid growth in non-dispatchable renewable electricity generation (e.g. from solar and wind) was being reflected in the ‘emissions factors’ that form the basis for our clients’ ESG reporting. In Australia, for example, 27% of electricity in the National Electricity Market (NEM) came from solar and wind in 2022, up from 9% in 2017 and less than 1% as recently as 2009.

What we found surprised us. The use of official factors to calculate GHG emissions from commercial and institutional buildings typically overstates measured emissions by 10-20%. That’s a big difference and reflects the fact that published emission factors are not designed for use in reporting GHG emissions from buildings.

There are two main reasons for the discrepancy. The first is that official factors are calculated in arrears by governments following the IPCC’s Guidelines for National Greenhouse Gas Inventories in order to meet their UNFCCC reporting requirements. They therefore lag physical reality, often by more than a year. Government calculations simply don’t keep up with the growth in renewables and the retirement of fossils.

The second reason is more interesting and is neatly summarized in the following plot of a client’s building in Los Angeles, California, taken from our live dashboard. The brown dashed line shows the official GHG emissions factor provided by the U.S. Energy Information Administration (EIA) for electricity sourced from the local grid. The unbroken brown line shows what the emissions look like in real-time (15-min intervals) when the variable generation supply mix is taken into consideration – it drops during daylight hours, and for a few hours of the day it is in fact ‘zero’.

The consequence of using accurately calculated real-time GHG emission factors versus the ‘nominal’ (official) factors is illustrated in the difference between the red and the blue lines. The blue emissions line reflects the building’s electricity consumption pattern (energy demand multiplied by the EIA’s constant), including a slightly worrying spike at 4:15PM in the afternoon. The red line shows the building’s emissions reality. It also shows that the spike in emissions at 4:15PM is not real – because the building has no emissions at 4:15PM in the afternoon as the grid is 100% renewable at that time. On the other hand, the spike at 7:00AM had significant carbon pollution associated with it and is worth the building manager’s attention.

Wherever the sun shines and the wind blows, renewables are driving down the price and carbon intensity of electricity. Grid-interactive efficient buildings are essential for making our energy infrastructure more stable and resilient and for targeting demand to accelerate renewable energy investment. They are also cheaper to run and provide better indoor environments.

That’s why all Buildings Alive clients now receive real-time GHG emissions profile data and analysis as part of their subscription. As one of the 40 founding signatories to the UN’s 24/7 Carbon-Free Energy Compact, Buildings Alive is proud to support building owners and operators that want to run on Carbon Free Energy 24/7.