@Andrew, when you monitor kW
@Andrew, when you monitor kW (demand), it becomes obvious that improving the shell or installing high efficiency A/C or heat pumps has a relatively small impact on peak demand (only to the extent that the AC or heat pump is downsized). There are plenty of studies that bear this out. Of course, hvac could be downsized on most homes without even touching the shell.

But without controls and storage, there’s nothing to prevent these loads from occurring simultaneously with other electrical loads, thus creating the peaks. For example, a second (or 3rd) air conditioner, hot tub, pool pump, electric water heater, range, electric drier….

The economic rationale for managing peak kW is fundamentally different than for energy efficiency. I agree that controls and batteries are expensive. But things look different from the utility’s perspective.

As I said, as long as residential rate structure ignore capacity costs in favor of energy charges, there’s no incentive for homeowners to invest in storage and control technologies. And without a mass market, costs are likely to remain high for the foreseeable future. But if and when demand charges become the norm for residential customers, controls and storage will become more relatively important than insulation and SEER in terms of reducing energy costs. So the question is whether the objective is to reduce carbon emissions, or to manage the cost of delivering power. Until and unless we have a carbon tax or cap/trade system, utility regulators (and politicians) will remain focused on the later. And the movement toward net zero homes and buildings is at odds with that.

David,
David,

Yes, it’s the Duck curve.

For those who don’t know what the duck curve is there is a pretty good chart here… http://www.greentechmedia.com/articles/read/california-needs-more-than-solar

Anyway, it seems to me that it would be cheaper to deal with peak demand, because of heating and cooling loads, with insulation. Battery storage and grid management has to be more expensive than insulation?

@Allison – Could you throw the duck curve chart up in this post?

“Zero Energy Home
“Zero Energy Home Program” in second paragraph should have been a link: http://1.usa.gov/1KyzciD

@Andrew, as I’m sure you’re
@Andrew, as I’m sure you’re aware, utilities around the country have recently been clamoring to dismantle net metering. Thus far these efforts seem to be driven by political forces, not by any serious or immediate threat to grid stability or revenue. But the problem is real. Just ask utility regulators in Hawaii. The problem is that today’s rate structures never anticipated homes that require full capacity support without billable energy charges. Yet, the economic rationale for rooftop solar and net metering rely on this dichotomy. At some point, something has to give. Or break.

The DoE understands this. Sam’s Zero Energy Home effort (formerly DOE Challenge Home) requires that participating builders meet aggressive EE requirements: DOE Zero Energy Ready Home Program. But this obviously doesn’t fully address the problem.

Prior to installing a net-zero+ PV array on my own home, I reduced consumption to about 3.3 kWh/ft2/yr. Hardly what you would consider an ordinary home. Yet coincident consumption averages less than 32% since peak loads are out of sync with peak production, even in summer (the duck curve).

Longer term, energy storage and smart controls provide the answer. However, traditional residential rate structures are a disincentive to customer-side storage and other load shifting technologies. Ironically, if rate structures were modified to encourage energy storage and smart controls, then we would be talking about how grid defection would eventually destroy the grid, as fewer and fewer customers would be left to bear the enormous cost of power plants and distribution infrastructure. So in a real sense, what’s beginning to play out is the battle for who will “own” these new technologies. But since neither the DoE or FERC have authority over retail rate design, this battle will play out in the states. Unfortunately, that foretells a very messy road ahead.

It actually does make sense.
It actually does make sense. Every kWh of PV generated you send into the grid prevents ~3 kWh of energy used at the plant. See my article on the four definitions of net zero, where I wrote that for an all-electric home, the site energy and source definitions are exactly the same.

That makes no sense. Exported energy would (should) be subject to a very different (lower) conversion factor for all sorts of reasons. Anyway, if that’s how they do it, then the net effect (for an all-electric house) is the same as net zero site energy.

It looks like ZEBs will meet heating demand with electricity (heat pumps). The sun won’t be shining much when it’s cold outside, and it won’t be shining at all when it’s coldest outside. So ZEBs in large part have to import electricity to meet their heating demand. This has implications for the grid, grid management and the need to build centralized generation to meet winter peak demand. This additional winter peak demand generation will likely have to be met with the construction of natural gas electricity generation. And with all that ZEB solar PV sitting on the ZEBs roof all those gas peaker plants will be sitting idle but for the period of peak winter demand.

And gas peaker plants will still be burning fossil fuels.

With the rapid decline in cost of PV on the roof top, it’s quite possible to foresee ZEBs with relatively high winter heat demand. It might be cheaper to build ordinary and then put an extraordinary amount of PV on the roof. This might be cheaper for the builder or future homeowner, but a much more expensive approach from a system, grid, perspective.

A ZEB is just a node in the grid, if it’s a ZEB with a greatly reduced heating demand then it’s one that will make the grid more resilient. If it’s a ZEB with a high heating demand then the challenge of meeting climate change obligations and transitioning to a post-carbon energy system are that much greater and more expensive.

I’ve focused on winter heat demand, I’m cold climate centric. : )

That said I do live in a jurisdiction where peak electricity demand is at the coldest time of the year.

On the flip side peak cooling demand also lines up with peak electricity demand in warmer climates, and the sun doesn’t shine on hot humid nights.

It’s nice that ZEBs are being better defined but I still get the feeling that they are being treated in isolation instead of being treated as part of the grid.

A couple of links from the EIA

Natural gas use features two seasonal peaks per year
http://www.eia.gov/todayinenergy/detail.cfm?id=22892

Does EIA publish data on peak or hourly electricity generation, demand, and prices?
http://www.eia.gov/tools/faqs/faq.cfm?id=100&t=3

David, no, that’s not that
David, no, that’s not that the way they do the calculations. For an all-electric home, you’d multiply both the delivered and the exported energy by the source energy conversion factor. That means that you just need to export the same number of kilowatt-hours or more to be a ZEB.

Their definition of delivered energy is:

“Delivered energy: Any type of energy that could be bought or sold for use as building energy, including electricity, steam, hot water or chilled water, natural gas, biogas, landfill gas, coal, coke, propane, petroleum and its derivatives, residual fuel oil, alcohol based fuels, wood, biomass and any other material consumed as fuel.”