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Honda opens Smart Home US in California; produces more energy than it consumes; direct DC-DC EV charging

The Honda Smart Home US integrates a number of technologies, and is managed by Honda’s Home Energy Management System (HEMS). Click to enlarge.

Honda marked the opening of Honda Smart Home US, showcasing technologies that enable zero net energy living and transportation, including Honda’s home energy management system (HEMS), a proprietary hardware and software system that monitors, controls and optimizes electrical generation and consumption throughout the home’s microgrid.

The home, located on the West Village campus of the University of California, Davis, is capable of producing more energy on-site from renewable sources than it consumes annually, including enough energy to power a Honda Fit EV for daily commuting. Honda Smart Home is expected to generate a surplus of 2.6 MWh of electricity over the course of a year, while a comparable home will consume approximately 13.3 MWh. The home’s occupant will be able to use less than half of the energy of a similarly sized new home in the Davis area for heating, cooling and lighting. The home is also three times more water-efficient than a typical US home.

A 10 kWh battery energy storage system in the garage, using the same lithium-ion cells that are used in the Honda Fit EV, allows stored solar energy to be used at night, when household demand typically peaks and electric vehicles are usually charged.

Honda’s HEMS leverages the battery to balance, shift and buffer loads to minimize the home’s impact to the electric grid. The system will also enable Honda to evaluate the second life, or re-use, of EV batteries in grid applications, home-to-grid (H2G) connectivity and other concepts.

Honda’s HEMS is also capable of improving grid reliability by automatically responding to demand response signals and providing other grid services. If the electricity grid is overloaded, for example, Honda Smart Home is capable of shedding its load and even supplying power back to the grid. This type of smart grid connectivity will enable the mass deployment of electric vehicles and renewable energy without sacrificing grid reliability, Honda suggests.

Among the technologies and green building concepts showcased in the Honda Smart Home US are:

  • Solar photovoltaics (PV). A 9.5 kW solar photovoltaic (PV) system mounted on the roof will generate more energy than the home and Fit EV consume on an annual basis, due in large part to the efficient design of the home. All of the energy for space heating, space cooling, ventilation, lighting, hot water, appliances and consumer loads, in addition to the transportation energy for the Honda Fit EV, is supplied by the solar panels on the home.

  • Fit_EV_Direct_Solar_Charging
    The Honda Fit EV included with the home has been modified to accept DC power directly from the home's solar panels or stationary battery, eliminating up to half of the energy that is typically lost to heat during DC-to-AC and AC-to-DC power conversion. Photo by Dorian Toy. Click to enlarge.

    DC-to-DC electric vehicle charging. The Honda Fit EV included with the home has been modified to accept DC power directly from the home’s solar panels or stationary battery, eliminating up to half of the energy that is typically lost to heat during DC-to-AC and AC-to-DC power conversion.

    When the solar panels are generating electricity at full capacity, the vehicle can fully recharge in approximately two hours directly from sunlight.

  • Geothermal radiant heating & cooling. In homes and cars, heating and air conditioning systems consume significant amounts of energy. In the ground beneath Honda Smart Home’s backyard, eight 20-foot deep boreholes allow a geothermal heat pump to harness the ground’s relatively stable thermal sink to heat and cool the home’s floors and ceiling throughout the year. Researchers from UC Davis will evaluate the performance of the system to determine its adaptability to mainstream use.

  • Pozzolan-infused and post-tensioned concrete. Concrete accounts for approximately 5% of global anthropogenic CO2 emissions. This large CO2 footprint is a result of producing cement—the concrete’s “glue”—by heating limestone to more than 1,000 degrees Celsius. This heating requires the burning of fossil fuels, while the chemical reaction itself also releases CO2.

    A naturally-occurring substance called pozzolan was infused into the Honda Smart Home’s concrete to replace half of the cement typically needed. A technique called post-tensioning, which uses steel cables to compress the concrete slab, was also used to reduce the amount of concrete and steel needed. Watch videos on pozzolan and post-tensioning.

  • Advanced lighting. The LED lighting used throughout the home is not only five times more energy-efficient than conventional lighting; it is also designed to support the health and wellness of the home’s occupants. Honda worked with researchers from the California Lighting Technology Center at UC Davis to explore new circadian color control logic.

    Mimicking the natural shifts in daylight that occur from morning to night, the circadian-friendly lighting design allows occupants to select lighting scenes that complement occupants’ circadian rhythms and support nighttime vision. The amber hallway night lights, for example, provide enough light to navigate through the home in darkness without depleting a photopigment in the human eye called rhodopsin that helps humans see in low-light conditions. This allows occupants to move about safely and return to sleep quickly and easily. Exposure to bright, blue-rich light during the day helps put body and mind in an alert and energetic state, but at night, blue light can disrupt circadian sleep cycles. Therefore Honda Smart Home minimizes the use of blue light at night.

  • Passive design. Honda Smart Home is designed to be extremely energy efficient by taking into account local weather conditions, sun direction and the home’s outer shell. Known as “passive design,” these techniques reduce the energy needed for heating and cooling while maintaining comfortable living conditions.

    The Honda Smart Home’s south-facing windows are optimized for heating and cooling, while the north-facing windows are positioned to maximize natural light and ventilation. This will keep the home naturally cool in the summer and warm in the winter. Double stud walls, cool roofing material and a fully insulated concrete slab all contribute to the home’s energy efficiency.

  • Sustainable materials & waste management. Sustainable materials were used throughout the construction process. Rather than cover the concrete foundation with wood, diamond pads were used to create a smooth, polished finish. For the roof, metal was selected, which is more recyclable than asphalt. All lumber used in the construction process was sustainably harvested from forests certified by the Forest Stewardship Council (FSC), while advanced framing techniques were used to reduce the amount of material needed. Honda Smart Home will seek a number of “green” certifications, including US Green Building Council’s LEED, National Association of Home Builders’ National Green Building Standard and U.S. EPA’s Energy Star. Finally, 96% of the construction waste associated with the project, including drywall, brick, plastics and lumber, was recycled.

  • Water efficiency. In a typical home, the toilet alone can use 27% of household water consumption. Dual-flush toilets with WaterSense certification, along with low-flow faucets in the sinks and showers and a high-efficiency washing machine and dishwasher all contribute to water savings. A technique called xeriscaping was used in the garden, where 30% of a typical home’s water is consumed. Plants that thrive naturally in arid climates were selected, while filtered greywater recycled from the home is the only source of water other than rain.

The Honda Smart Home US was designed to address specific challenges associated with the transportation and energy sectors in the United States. California’s Energy Efficiency Strategic Plan, for example, sets a goal for all new homes to be zero net energy beginning in 2020.iii Through a combination of advanced technology integration, energy efficiency measures and sustainable design techniques, Honda Smart Home surpasses that goal by producing enough energy to power the home and an electric vehicle on a daily basis.

Hundreds of channels of energy data generated by sensors throughout the house will be shared with PG&E and UC Davis researchers. In addition, Honda’s Environmental Business Development Office, in conjunction with Honda R&D, will use the home as a living laboratory to test new technologies and evaluate new environmental business opportunities.

Honda Smart Home US, construction of which began in April 2013, will serve as a residence for a member of the UC Davis community; the selected member will soon be announced. The fully-furnished home comes equipped with a Honda Fit EV battery electric vehicle for the resident’s daily transportation.

Together, energy used to power homes and light duty vehicles contributes to approximately 44% of US greenhouse gas emissions in the United States. Technology that enables distributed renewable energy generation to supply power to homes and cars seamlessly is one of the key potential pathways to address climate change, Honda notes.

UC Davis’s West Village, where the Honda Smart Homes is located, is the largest planned zero net energy housing development in the US. Opened in 2011, West Village is home to university research centers focused on energy efficiency, sustainability and transportation.



The use of DC particularly intrigued me, but of course there are a raft of developments here to be assessed.


More efficient houses are being built in Japan and Germany. Those new houses use less energy from the grid than they push back in. In other words, you get enough free solar energy for all house usages including charging the home EV or two and more.

A country with enough of those smartly built houses would not have to build more Power Generating Plants nor have to improve the power distribution grid.

It could be an excellent solution for California and all other Southern US States. If it works in Germany and Japan, it could work in almost 100% of the USA and southern parts of Canada.


Harvey, being energy neutral over the course of the year is NOT the same as being energy neutral.

In Germany demand in winter is massively greater than in summer, and plenty of fossil fuels are burnt to cover that.


I wonder if it is affordable with 9KWh of solar panel, 10KWh of batteries, geothermal heat pump and others nice devices....technologies are only beautiful when they get affordable, otherwise they are just expensive work of art


Harvey, being energy neutral over the course of the year is NOT the same as being energy neutral.

This is true, but the solution to that is to build an energy-plus house. One that has enough PV + batteries to almost always be putting energy into the grid rather than taking it out. If not blocked from direct sun the roof of the average house is large enough for that even in winter.



It all depends on where the house is.
In southern California the gap can be bridged as there is substantial demand in the summer for air con, and winters are not usually very cold.

That is not the case in other climates and especially not at higher latitudes.

Even your remark about the size of the roofs depends on where, as US roofs are bigger than most other places.

Treehugger has made the critical point though.
Throwing more resources and putting more and more capital equipment in is not a free ride, and depending on the climate can become very expensive indeed.

This set up would not be cheap even sized for the modest winter heat needs of Southern California, and their comparatively low latitude.


Which begs the question of

  • who or what is going to be able to make use of these surpluses, and
  • how are they going to cope with the (very frequent) event when those surpluses suddenly disappear?

It's the "duck belly" problem writ large.  The only real solution is to force the PV owners to either install or buy a share of some form of storage which time-shifts their noon-peaking generation to the evening demand peak.  Since this is only for a few hours but is cycled daily, some form of storage can be uesd that may be relatively expensive per kWH but is cheap per cycle.  A flywheel might be ideal so long as the losses be kept to 1% per hour or so.


The grid will be required to share-manage,

1. short and long term energy surpluses
2. short and long term energy shortages

unless each house or group of apartments are equipped with enough short term storage such as (batteries?) and/or long term storage such as (electrolyser + H2 storage + FC + DC/AC convertor).

Solar systems work best in sunny warm places where high demand corresponds with high energy production. That is not the case in northern places.


"The Honda Fit EV included with the home has been modified to accept DC power directly from the home’s solar panels or stationary battery..."

I recall someone on here saying that you never do a battery to battery charge. That was stated in a most absolute way, conveying total knowledge.


Even your remark about the size of the roofs depends on where, as US roofs are bigger than most other places.

This is true, but smaller roofs usually go with smaller houses which are more energy efficient.


It's true that it's a bad idea to connect two large batteries of different terminal voltages to each other; the surge currents can be immense.

Using DC-DC converters is another matter entirely.


Building to passive house standard would make any of these technologies smaller and therefore more affordable. For example, Builder Rich Millburn of Sonoma California, told me while I was making the film Passive House Revolution, that because he had retrofitted the house he was showing me to passive house standard it only needed 14 PV panels instead of 34. That's a considerable financial savings.

I believe that we have to start with reducing energy use - then look at all the technologies for producing and saving/storing energy from renewables. If I recall correctly, Germany's energy mix is about 25% from renewable sources - yet last year their energy use and CO2 out put increased.

If we really believe that climate change is happening and that we humans might possibly be making it worse by burning fossil fuels, then we can't ignore the need to curtail its use.


My first post, hadn't meant all that last to be italic - I will review before posting next time!


Posters on this site have been critical of the idea of using excess electric output to produce hydrogen and then reuse it through fuel cells. While not currently cost effective, I think it sounds like a viable solution for storing excess renewable energy to manage load both short-term (daytime variations) and long-term for seasonal variations. Maybe it is not a total solution, but one of many.


"Germany's energy mix is about 25% from renewable sources - yet last year their energy use and CO2 out put increased."

This is true but it's not the whole story. Their energy use went up more than they CO2 so they were actually burning less carbon per kw generated. In fact their big fossil fuel powered utilities were losing money - that should tell you something.

They were also emitting less CO2 per GDP. That should also tell you something. BTW it's not just power plants that emit CO2. Germany is recovering from the global recession and as Europe's most industrialized nation that means CO2 from the building sector (cement production), more consumer goods sold (CO2 from steel production), more CO2 from vehicle traffic (those goods/building materials & people have to be moved around), add in the fact Europe also got hit by the other side of that polar vortex which means greater home heating and it's surprising their CO2 emissions only went up 1.6%

Bob Wallace

Actually it appears that Germany's CO2 output did not increase in 2013. Some reporter jumped the gun and used partial year data to project CO2 emissions for the entire year. Now that data for the rest of the year is being released it looks like 2013 will be a bit lower than 2012.

Bob Wallace

The California duck graph is somewhat of a cherry-picked worse case day.

There will be a need for morning and late afternoon supply to fill in around solar. Thermal solar with storage is one answer. Importing wind from Wyoming is another.

Work is underway to build a HVDC line from Wyoming to the Pacific Intertie and Intermountain Intertie. That would create a loop that would tie together the Pacific Northwest, SoCal, Utah, Nevada and Wyoming and allow sharing of PNW hydro, SoCal solar, Nevada geothermal, and Wyoming wind.

SoCal (Arizona and New Mexico) can provide solar during the day. Wyoming wind starts really kicking in in the late afternoon. The PNW has hydo to smooth things out. Storage and backup can be shared.

Bob Wallace

"That is not the case in other climates and especially not at higher latitudes."

Europe has been building 'zero energy' houses for a while. Houses that produce as much energy as they use. Here's an example from Denmark.


Here's one in Sweden...



Yes BW, USA and Canada spread out over 5 different time zone and could share clean Solar and Wind energies.

As more and more Solar and Wind energy is harnessed, more storage will be required. Batteries may be OK for short time storage but the H2 avenue may be required for long time seasonal storage.


"Actually it appears that Germany's CO2 output did not increase in 2013. Some reporter jumped the gun and used partial year data to project CO2 emissions for the entire year. Now that data for the rest of the year is being released it looks like 2013 will be a bit lower than 2012."

Well I took the "last year their CO2 out put increased" statement to mean 2012 not 2013 because I had heard 2013 was showing CO2 going down again.



    I agree that efficiency is not the only consideration all the time. We turn on lights when power plants are 30% and lights are 10%.

Here is a hopeful italic killer comment.  (crosses fingers)


Well, foo.

Nick Lyons

To Fay: to use Italics, please use tags <i> to begin Italicized text, </i> to end. Thanks.


Thanks Nick

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