Going beyond ‘Net Zero’ to Passive House

By Tad Everhart

Going beyond ‘Net Zero” to Passive House by Bronwyn Barry, President of NAPHN, and Mei Shibata at Essense Partners was published by Utility Dive, a trade publication for electric utilities, but it is instructive for those of us who look at the grid from the other side of the meter, from the homeowner’s point of view.

Even a Passivista might read the title and think, “Wait a second, they’ve got that wrong.  Isn’t a Passive House something that’s less than a Net Zero home?  Passive House is how we reach our highest goal, the Net Zero energy home.”

And in the popular imagination, there is no more energy-efficient building than a Net Zero building since it imports no energy.  Yet we all know that is not the case unless the Net Zero building is also off-grid.

Simply defined, the Net Zero building simply exports as much electricity as it imports.

And it need not be as energy efficient, let alone more energy efficient, than a Passive House.

Does it matter?

Yes.  From the utility’s point of view.  Energy efficiency and generating capacity are much different.  And the difference matters to utilities.  A lot.

If you think of the relationship of a consumer and a producer as a partnership, the Passive House may be a better partner customer for the utility than some Net Zero buildings.

In many regions, utilities are customers as well.  They buy electricity from others.  And transport and distribute to us.  They always consider maximum seasonal loads.  That’s when there is little excess generating capacity and electricity may be more expensive.  Much more expensive.  If that is in the dark, cold winter, the Passive House may be a better partner for the utility than a Net Zero building.  If the Net Zero building imposes a greater daily load and seasonal demand than a Passive House, it is a customer which is harder and more expensive for the electric utility to serve.

Our electric utilities provide the electricity a Net Zero home needs when onsite generation is insufficient to meet hourly, daily, or monthly demands.  It’s easy to think of the electric utility as a bank.  However, that’s an oversimplification.  And the authors show why.

In banking, money has the same value regardless of when it is withdrawn or deposited absent inflation.  With a bank, you can make deposits and withdrawals regardless of regional and seasonal system-wide supply and demand, and your money has the same value.  Banks are as happy to take your deposit when many other depositors are depositing their checks after payday as banks are for you and many other depositors to take money from your account or use your credit line at the end of the month before you get paid.

With energy, time of use matters.  Electricity’s value depends on supply and demand at a particular point in time.  And not just during a day where we know the shifting balance of supply and demand from the well-known duck curve contrasting daily peak onsite electricity generation and demand.

Time of use during the year matters.  The season matters.  Especially in cold climates with skimpy winter solar gain, the winter season taxes utilities.  Even if all buildings in the grid are Net Zero, on a cold, dark winter day, aggregate onsite solar PV production will likely be a pittance compared to the peak loads.

Recent regulatory skirmishes between utilities and the solar industry illustrate the mismatch of onsite solar electric supply and electric demand.  Utilities are loathe to pay retail rates for excess electricity from customers’ rooftop PV if there is little or no demand for it at the time it is generated.  If they don’t need it, then it has little or no value to them.  It may actually be a nuisance.  Yet regulators are forcing them to buy it.  And they are not enthusiastic about simply netting the annual balance of electricity imported from and exported to a Net Zero homeowner.  Especially if they must pay higher costs for electricity they purchase during periods of peak demand and resell at the same fixed, annual retail rate to the Net Zero customer.

 

The article does not bash Net Zero buildings, and nor should we.  Passive House and onsite PV are a great match.  Both are necessary for a 100% renewable electricity-powered world.

Passive House and the Net Zero community should be allies.  Every Net Zero home should also be a Passive House to ensure the lowest load on the grid.  And Passivista should encourage their homebuyers to install renewables onsite if appropriate and/or purchase offsite generating capacity to offset their load.

Going forward, both communities must consider the challenges electric utilities face and work with them.  Passive House is one of the tools for creating a Net Zero building that goes easy on the utility’s grid when onsite renewable resources are scarce.  And the inherent appeal of a Net Zero building is a great way to inspire consumers and building occupants to achieve Passive House energy-efficiency.  Inspiration and enthusiasm are necessary for people to tackle the challenge and higher first cost of Passive House buildings.

The article helps start a conversation about how we best and most quickly achieve the 100% renewable energy future.  Thanks to Bronwyn Barry, Mei Shibata, Essense Partners, and Utility Dive.