The problem with Net Zero: The grid is not a bank

George Bailey
Video screen capture No, you can't withdraw energy when you want it, either.

Sponsored posts are a form of advertising; they help keep the lights on at TreeHugger. They are usually anodyne and uncontroversial. So it was odd to see one on Utility Dive that is strongly dissenting of the accepted wisdom about Net Zero.

Now I have to preface this by noting that I am confused about Net Zero and never quite sure what people mean by the term; there are so many standards and variations. The simplest definition that I do understand comes from the International Living Future Institute: "One hundred percent of the project’s energy needs being supplied by onsite renewable energy on a net annual basis." That seems all very admirable but what I don’t get:

  • As solar power gets cheaper and cheaper there is less and less incentive to actually design a good energy efficient envelope delivering a really comfortable interior;
  • Rooftop solar disproportionately favors those who have rootops, preferably big ones on one-story houses on big suburban lots. Those people tend to drive a lot.
  • And finally, and the issue the article addresses, is the question of “net annual basis” -- Net Zero projects generate excess electricity in the summer and need a utility to accept it, and then rely on the utility to supply power in the winter.
Katherine making pizza© TreeHugger Katherine making pizza which is converted to money which is put in a bank

One analogy might be the pizza and bagel joint just up the road in cottage country (it’s run by TreeHugger Katherine’s sister, read about it here). Sarah Jane works like mad during the tourist season and makes enough money to put in the bank and get through the winter. Financially, she net zeroes between the seasons. But she can convert pizza and bagels into something that she can store. Because, as the anonymous author of the post notes,

The grid is not a bank.

Run on bankIt's a wonderful life/Screen capture

During the run on George Bailey's savings and loan in the movie, "It's a wonderful life," he had to explain the loan part.

You're thinking of this place all wrong, as if I had the money back in a safe. The money's not here. Your money's in Joe's house ... and a hundred others.

There's no vault full of energy either, when you deposit it into the grid. The post author notes:

Understanding that the grid is not a bank is key to recognizing that current ‘net zero’ accounting could lead to suboptimal building design outcomes. Buildings are being incentivized to include on-site renewable generation, but their arrays are not being sized according to their winter peak load, but rather as if the grid was functioning as a credit system that stores energy for later use.

But the grid doesn’t store energy from the summer for use during the winter. It can barely store energy at all except in the form of coal and natural gas and uranium.

energy summer and winter© Bronwyn Barry

The reality is that the grid does not have the capacity to store all excess energy generated in summer, so buildings employing this ‘fuzzy math’ still require that the grid supply their winter deficit. Unfortunately, this winter energy is more likely to be generated using fossil fuel sources and therefore buildings designed in this manner are still responsible for the higher carbon emissions generated by non-renewable energy sources.

What’s the Solution to The Winter Problem?

The author suggests that instead of writing net zero into the codes, we should “tackle the issue on the customer side, by actively minimizing the building’s winter heating demand.” This is what I have been advocating for years, using New Zealand architect Elrond Burrell’s term, Radical Building Efficiency, to build levels of insulation into our homes and buildings so that they don't create the peaks of demand at times when the renewables aren't there to meet it. Or, as Elrond Burrell describes it,

Stringent space heating and cooling energy targets along with comfort targets ensure that the building fabric has to do the majority of the work. The building fabric, which will last the lifetime of the building, will be highly energy efficient and ensure a comfortable building by design, regardless of how and where the required energy is generated.

We have a summer problem too.


The winter problem is serious, but right now in parts of America we have a summer problem, where temperatures have reached ridiculous highs in the Northwest and people are installing air conditioning systems like mad. Getting to net zero is a lot tougher when you have to supply AC in summer, especially if you didn't design for it. Those solar panels also probably don’t work as well when the air is full of smoke and they are covered in soot.

When you can’t even rely on the sun anymore, it’s time to get serious about reducing demand with Radical Building Efficiency. Call it Passive House, call it whatever, but it’s better than the "fuzzy math" of Net Zero.

Tags: Energy | Energy Efficiency | passive house

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