All posts by Kyle Field

Putting A Price On Home Energy Efficiency

Originally published on CleanTechnica

Buying a house is an exciting part of life, the start of a new chapter, and frankly…freakin’ scary! Typically that’s not because of any spooky creatures but because of the massive mortgage that people usually take on to afford one, the number of things that can go wrong, and unforeseen financial burdens that these ‘money pits’ can become.

Many of the financial pitfalls can be identified early on in the buying process as part of a quality home inspection, but there’s one big dirty secret that many homes have that is a bit harder to wrap your head around when buying a new place – energy. I’m not talking about the qi (or ch’i) of the house or anything like that, but literally about the energy used by the house on an annual basis in all forms – electricity, natural gas, propane, heating oil, solar, wind, solar thermal, geothermal, etc

Let’s back up a bit. Pretend you’re buying a new car. Do you check the window sticker to see what options it comes with? How about the fuel efficiency? Estimated cost to operate for a year? Me too! …and it’s the same for a house. We want to know which energy options it comes with. Does it use natural gas for heating? Have a high tech heat pump in the basement that is dirt cheap to own and operate?

Fuel efficiency similarly translates into energy intensity. You thought I was going to say energy efficiency there, right? The actual metric for putting data behind this is the amount of energy used per square foot of the house. Roll that up over the size of the house and the months of the year and you get the mega-metric – the total cost of energy to operate for a year.

Before cars kept track of fuel efficiency, knowing what miles-per-gallon your car got was irrelevant to the market – you don’t care what your car gets and the market doesn’t value it…and it’s the same thing with a home. You can invest $15k in solar panels, $10k in energy efficiency improvements, and $3k in a new heat pump, but you’re not going to see much of that money rolling back into the valuation of the house because people don’t speak that language yet.

We need to retrain our brains, and the market, to accurately value not just the cost of the house but the cost to run the house month to month. For example, let’s dig in to the numbers on two houses:

  • House A is $1000/month to buy for 1700 square feet, but costs $300/month for the electricity bill and another $150/month to heat it.
  • Across the street, House B is also $1000/month to buy for the same 1700 sq ft footprint, but due to the solar panels on the roof and the extra insulation in the walls, floors, and ceiling, only costs $50/mo for the heating bill, with no electric bill to speak of.

Obviously the second house is worth more, and is a better value for the same purchase price. But just how MUCH more does an energy bill that’s $400 lower (every month!) make the house worth? Backing up a bit, how do we even quantify the monthly cost of energy for a house?

Putting a price tag on the cost of energy is the first step in getting a handle on the value of residential renewables – such as solar – into the valuation of the house. That allows homeowners to see the month-to-month cost and quickly extrapolate the cost of energy over the life of the house (the long term cost of energy).

This could be accomplished by reapplying the concept of the Energy Star label on appliances:


Beyond just the base concept of putting a dollar value on, and an increased visibility of, the cost of energy, less efficient homes are actually more risky to banks. Think about it. In the example above, house A carries an energy bill of $450/month vs house B with just a $50/month bill. That’s an extra $400 of monthly debt on house A that will never go away for the homeowner.

That effectively takes the monthly payment for the house from $1000 to $1450 whereas House B is only going to cost $1050/month – a huge difference. One of my favorite sayings that I’ve heard about solar is that it takes a monthly liability (the monthly bill) and turns it into an asset (increased value of the house).

Homes with higher energy bills are riskier investments for banks, as the monthly energy cost is not taken into account when the home is financed. It’s essentially a highly variable chunk of debt (particularly in this era of increasing efficiency and solar) that the bank not only doesn’t know about, but doesn’t seem to care about.

In markets where the energy bill is a large percentage of the mortgage, this can play a large factor in whether a homeowner can actually afford the full cost of the home or not. Further, the variations in energy price can, and likely often do today, single-handedly sink the homeowner’s monthly budget and kick the loan into default.

Finally, these energy costs can be rolled up over the life of the loan as part of the purchasing process. House B might only cost $18k in energy costs over 30 years whereas house A would tip the scales at $162k!! Granted, not many people are interested in stepping back and looking at the total cost of energy over 30 years, but lifetime costs often paint a picture compelling enough to trigger small changes.

If we looked at energy costs this way more often, solar and energy efficiency would be much more likely to have increased value when the house hits the market. Markets value what is measured. We need to measure energy use and turn consumption into an easy to understand comparable metric – like MPG is for fuel efficiency.

Doing that will trigger banks and financial institutions to dig a bit deeper into the value of energy efficiency and residential power generation as a part of the lending process and overall risk assessment. If Energy Use Intensity is being looked at by financial institutions, services like Zillow will start reporting EUI, which completes the cycle back to the consumers.

Homeowners would have more incentive to invest in technologies that are better over the long run and often for the planet, such as making that $5k investment in more insulation, spending $300 on LED light bulbs, or $15k on solar. Homeowners can have the confidence that they are making an investment in the house and in a reduction in monthly operating costs over the life of the home, or at least of the product being installed. For LEDs, that’s just 22.6 years…what a ripoff :)

EV Charging — The Time For A Single Fast-Charging Standard Is Now!

Originally posted on CleanTechnica

The EV charging network is the gas station network for EV owners — the only place to fill up and top off when out on the town, driving around the fringes of an EV’s range. What’s more, charging up an EV takes longer than fueling up an ICE vehicle, so the quantity and availability of charging stations makes a huge impact on the functionality of EVs. To further complicate matters, the growing fleet of plug-in hybrid electric vehicles (PHEVs) that don’t have the same “need” to charger can frequently be found charging at public EV charging locations, blocking out battery electric vehicle (BEV) drivers that, as a result, might not be able to get the charge they need to continue to their destination.

As BEVs and PHEVs increase in popularity, the current public EV charging infrastructure will also need to be scaled up to support the fleet. The lack of an EV fast charging standard further complicates the landscape, fragmenting the already struggling infrastructure with several standards competing for dominance, and manufacturers are drawing lines in the sand and picking teams to determine which standard will reign supreme.

Where We Came From — Level 2 Charging

With the initial deployment of EVs, what we now call Level 2 chargers were deployed far and wide to incentivize the public to purchase electric vehicles. These chargers provide charging rates of 6.6 kilowatt-hours for each hour of charging. In a Leaf, that equates to around 24 miles of range per hour of charging. These chargers were a fantastic start at developing a public charging network and gave early adopters the confidence to purchase a $30,000 vehicle with a reduced range.

Level 2 public chargers allowed people to extend the practical range of their EVs with just a few hours of charging required to top off their charge before heading on to another destination. Level 2 chargers are now installed in garages of many EV owners and the public network of chargers has only continued to grow as EV adoption has increased.

Building a Better System — Early DC Fast Charging

To complement these chargers, Level 3 chargers — or DC fast chargers — have started popping up. Level 3 chargers brought a significant advantage to the table in terms of charging speed and were able to push ~19 kWhs in a 30-minute session, equating to the addition of roughly 80% of the charge or an extra 76 miles of range. Charging rates slow as the battery nears the 90% full range, so, your mileage may vary.

DC fast chargers have grown into the gas stations of the EV charging network in most areas, as they allow ~80% charge in the time it takes to enjoy a cup of coffee or grab a bite to eat.

Similar to early Level 2 chargers, Level 3 chargers are expensive, with installations requiring significant electrical infrastructure in addition to a hardware cost upwards of $100,000 each in the US. Due to the high capital cost required to install Level 3 chargers, early installations have been slower and mostly implemented by companies dedicated to charging infrastructure likeNRG EVgo and ChargePoint. These chargers started popping up in major cities, then made their way into smaller cities across the nation.

DC Fast Charging Today

Which brings us to today. In the southwestern United States, we have a healthy network of Level 2 chargers supported by a sprinkling of Level 3 DC fast chargers. On top of this mature network, EV sales have ramped up and are weighing heavily on our primarily Level 2 charging network. Many modern EVs are equipped with fast charging capability, with many supporting higher speeds than the current networks even provide. As we approach the next step change in EVs — with ranges of 200 miles requiring batteries of 60 kilowatt-hours and more — we are again approaching a point where even our fastest chargers today will not meet the needs of the masses.



Kia Soul EV CHAdeMO Adapter (on right) | Image Credit: Kyle Field

CHAdeMO plugs are the size of a large firehose, making its charging cables unwieldy, and it is the fast charging adapter of choice for the Kia Soul EV, Citroen, Mitsubishi EVs, Peugots, and of course, Nissan and the established Leaf (as an option). CHAdeMO offers charging speeds of up to 70 kW, with real-life 30-minute charging sessions delivering just over 19 kWh of charge or around 75 miles of extra range (on a Nissan Leaf). CHAdeMO is seeing extremely rapid adoption in Japan, with around 5,500 stations deployed today (crazy considering how small Japan is!). The US — specifically, California — is ramping up deployment of CHAdeMO stations quickly as well, where over 1,300 stations have been deployed.

SAE Combined Charging Solution

Competing with CHAdeMO for the DC fast charging crown is the newer SAE Combined Charging Solution (aka SAE Combo, or CCS), which is a standard J1772 plug with 2 additional DC fast charging ports below it (hence the combo moniker). This newer standard is the fast charging standard of choice for Audi, BMW, Daimler, Ford, General Motors, Porsche, and Volkswagen. Most notably, this port can be found on the BMW i3, the Chevrolet Spark EV, and the Volkswagen eGolf. Combo adapters are similar in size to CHAdeMO, though due to the utilization of the existing J1772 plug, only require a single port on the car, whereas CHAdeMO requires 2 separate on-vehicle ports.

These Combo plugs offer maximum speeds of up to 90 kW (DC Level 2) with theoretical speeds of up to 240 kW. In real life, SAE Combo charge rates are comparable to CHAdeMO, delivering roughly 80% of the range of ~100 mile EVS in a 30-minute fast charging session.


Tesla Supercharger in Oxnard, CA | Image Credit: Kyle Field


Finally, the Tesla charging format supports all charging levels from Level 1 (normal wall outlets at 110 volts) up to the Tesla-only DC Supercharging network which boasts the fastest broadly available charging speeds, cranking up to 400 miles of range per hour (design rate) with a real-world miles delivered in 30 minutes of Supercharging sitting at 170 miles. This does not scale up linearly (170 x 2 = 340 miles of range delivered per hour), as charging slows when the battery approaches capacity — but it’s still extremely impressive and much faster than any other fast charging standard with a substantial deployed footprint.

The Tesla charging standard is also much more compact than the other standards and can be used for all charging speeds — from 110v wall charging @ 15 amps all the way up to Supercharging.

The Road to the Future

Where to from here? Ultimately, the market will decide which manufacturer and, thus, which standard prevails. Manufacturers are realizing the negative sales impact the current, scattered public charging network is having and building out branded charging networks. Much like the VHS vs Beta or the HD-DVD vs Blu-Ray battles of the past, fragmented landscapes rarely last for long. We will likely converge on a single standard, but the longer the transition is drawn out, the more consumers — and EV adoption rates — will suffer. We need a fast charging standard now to give manufacturers and consumers confidence in EVs long into the future.

Several clear paths exist — though, with sides having already been chosen, no option will be pain-free. An NGO or charging alliance could be formed as a neutral self-governing body to select a dominant standard moving forward. Though, this is challenging as these organizations cost money and offer little financial upside for participants. Government mandates can also create results and that feels like what may be required to unify manufacturers as an effort to protect consumers from non-value-added infrastructure fragmentation.

Whatever the path forward, the time for action is now. Consumers are calling out for a single EV fast charging standard to carry us several decades into the future….

My Epic Tesla Road Trip

Originally published on CleanTechnica


Upon rolling out of the Tesla Dealership… er… Service Center in Columbus, Ohio, a few things hit me right off the bat: The new-car feeling, realizing that this was my car. The realization that now I really was pretty much on the other side of the country and actually had to drive back across the ~3,700 kilometers at around 33 hours of driving. The fact that I only had one room booked between Ohio and Vegas … and what the heck, I just bought a Tesla!?!

I wanted to take off like a bat of hell and drive 120 miles an hour down the road, tearing up the asphalt… but I’ve been there and done that and tickets (and accidents!) are expensive no matter what state you’re in. So I calmed myself down, took a sip of the coffee CJ had so generously hooked me up with, set the cruise control for 65, and pointed the wheels to the west.

The next day, after a few hours of rest, several stops at Superchargers, hundreds of miles, and too many cups of coffee, I had a good feel for the car and how it worked on long road trips. While the car generally met my expectations, a few things stuck out to me about the car that I hadn’t expected.


Supercharging in Columbia, MO

Automagic Unlocking

Locking the car, for one. The Model S automagically locks (it’s an optional setting) when the driver walks away with the key fob. At first, I would nervously look out at the car from the gas station, coffee shop, or lunch stop to confirm that the handles were in, lights were off, and all that. After several stops, I realized that it just works. Put it in park, get out, walk away, and you’re good. It’s awesome. No parking brake, no locking or unlocking the car… easy.

Power at Your Fingertips

The power of the car is also amazing. With a single-motor, non-performance version of the Model S, I was not expecting amazing performance, but it blows me away. I used to have a ’97 Pontiac Trans Am, which I had done some work on, so I’m familiar with performance cars, but the smooth, torquey power of the Model S is a different beast altogether, and a lot more fun in my opinion.

Going 30 but want to go 65? Done. Going 65 and want to pass the smoggy diesel pickup in front of you? No problem. It’s something I’m still working on dampening, as it just begs to go faster than most laws allow. My favorite is pounding the pedal while cruising at around 20–30 miles per hour. It jumps like nothing else… okay, except may be a P90D with Ludicrous Mode :D.


Supercharging in Colorado


I will go into more detail about Supercharging in a separate article, but suffice it to say that it blows the competition away. Triple the speed of the next fastest charger, predictable, built into the navigation, and easy to use. It’s great. I loved being able to punch in whatever destination I wanted, however far away, with the confidence that the car would navigate to the nearest charger automatically.

Most of the Superchargers were located at hotels, gas stations (of all places!), shopping plazas, and otherwise near facilities that could occupy 30 minutes of a day, which was nice. A few stops required a bit more creativity to answer the calls of nature or get a bite of food. I found the ability of the car to keep the heating on while charging to be a great feature that I took advantage of extensively on my journey.


My favorite Supercharger — at a BP gas station in Effington, IL

Indecisive Navigation

One glitch that I noticed in the navigation is that, after topping up at a Supercharger then heading down the highway, the navigation would occasionally try to route me back to the charger I had just left (after charging for the amount of time it told me to charge for).

This even happened a few times after I was 20 minutes down the road like it suddenly realized I needed more capacity to make the next charger. It did not make sense to me, as I typically had 50–80 miles of “spare” range above and beyond what was required to get to the next charger. It was not a deal breaker and I was able to manually navigate through it by turning off charging stop recommendations, but it seems like a bug in the logic that could be corrected.

Navigation Range Estimation

Along similar lines, the navigation is conservative, but with caveats. First — it is conservative as it tries to ensure that you have WAY more charge than needed to get to the next destination. If I’m going 65 miles to the next charger, it wants me to have at least 110 miles of range to move on.supercharging

The caveat to the estimated range is that external factors like elevation gains, climate controls (heating/cooling), driving speeds, and outside weather can (and did!) have large impacts on range. It was not clear if the navigation was actively taking those factors into account — or at least for the static, predictable factors — but it seems like it could more accurately describe why it wants more charge at certain times.

On my trip, I drove over the Rocky Mountains (very steep, cold mountains in the Western United States), drove in sub-zero temperatures, and as a result, used the cabin heating frequently. I was aware of the impacts these would have, but an unfamiliar driver, not realizing the interrelationships between these factors could easily end up stranded in their Tesla. These factors are also present in gasmobiles, but with gas stations on every corner and most freeway exits, it is less of an issue. Growing pains…

The video below details some of my jumbled learnings from the road. I was happy to find that the speedometer display was the right angle to capture this specific angle with my phone, making it easy to record videos and video chat with my kids while out on the road. Technology is amazing.

All images and videos by Kyle Field

EVs & PVs — You Can Drive on Sunshine!

Originally published on CleanTechnica

This is an overview for how to assess a solar installation for a residential property and pair the system with an EV or two to generate your own power and drive on sunshine. This is not an attempt to document every scenario, but rather to share the overall direction and flow from which you can, with your newfound knowledge, move forward with an installation of your own. Let’s get started!

When we first put solar panels on the roof of our 2-story home here in sunny Southern California, I understood the concept but had some questions about how it all actually worked. It was quite the learning process, and since then, I have continued to add panels to the roof to offset our base usage while also adding more load to our system with the addition of 2 EVs in the last 12 months. With all this, we are now living the dream and effectively “driving on sunshine.” As there were so many learnings with both systems, this article will help frame both pieces of the puzzle in order to help others understand some of the nuances and how they work together.

The Roof today with our 17 solar panels

The first step towards getting solar panels up on your roof is sizing the system. This is one of the first steps a solar installer will typically do for your site, but you can also go through it yourself to understand the details or for a DIY installation. Many factors dictate system size but the two big ones are the usage you want to offset with new solar generation and the solar potential of the installation location.

Calculating your estimated usage is very straightforward, as your utility has a vested interest in tracking usage accurately so it can bill you for it. Look up the last 12 months of bills and capture the monthly usage in kWhs for each month. The resulting total is your starting point for annual usage. Next, take into account any big project that could impact your usage in the next few years — adding an EV (I’ll review estimating EV usage below), removing a hot tub, installing LED lighting, etc., and either add or subtract those from the annual usage total. Finally, determine what % of that usage you would like to offset. Most installers will use 90% of the production, as any excess is typically not a good investment for the homeowner. My personal goal is to continually generate at least 105% of my total usage.

To understand the solar potential of your location, use an online solar production potential calculator like PVWatts. You enter the key details of your system — some which take more work than others, like installation address, system size (from your work in the previous step), tilt, module type, etc., and the system spits out a nice annual chart of estimated production by month, including the value of the energy produced.

PVWatts Estimated Production

One of the first question folks normally ask about residential solar is “but, what about the batteries?” In most residential installations, the PV solar system will be connected to the grid, meaning that any excess energy produced will be sent to the grid. In a net metering arrangement, the utility will track how much the PV generation sends to the grid and keep a tally sheet, “netting out” usage vs generation at the end of the year. Why annually? This allows systems that generate more in the summer and less in the winter to level out over the year instead of the utility paying the customer in the summer and vice versa in the winter. This could be a whole separate article but I’ll leave it at that for now.

Now that we have our system sized up, let’s go get some bids from installers! I went with SunRun (previously REC Solar and recommend Evergreen Solar as a great unbiased solar installer finder) I’m not going to go into full detail on how systems are priced out, but there are primarily 3 options:

  • Buy this system outright with cash. The system is yours and all generation is “free” after the initial purchase.
  • Sign up for a Power Purchase Agreement (PPA). The installer will front the money for the system and you agree to buy power from them for a predefined term of 20, 25, or 30 years. Terms such as annual % price increases, duration, upfront cost, and savings vary. Do yourself a favor and read the fine print… that’s a long period of time to be locked into bad terms. 🙂
  • Financing. Finance the system through the installer. These contracts are getting sticky so definitely another one to watch out for. It may be better to finance through an unrelated bank to pay for the system vs finance through an installer. A great article on Solar Love flagged some key details on a new SolarCity financing scheme that seemed less than consumer friendly.

My Solar System's Production Summary

Before you lock in and sign papers, dig into the return on investment that the solar salespeople (yes, they are trying to sell you the system, even if it’s a zero-down deal) pitch to you. A few tips — look for price increases in the retail electricity they are comparing to. For instance, in my area, Tier 1 rates were $0.12/kWh when I signed up and they projected 5% increases every year. To validate that, I went in and flattened the price of electricity for a “worst case scenario” payback. Since 2011, however, we did offset the small amount of Tier 2 power we had been paying for ($0.19/kWh) and our Tier 1 pricing has gone up quite a bit and is now $0.15/kWh which is inline with the solar company’s projections.

I have also built an Excel sheet (as I’m prone to doing) to track our solar production, home usage, efficiency savings (improvements in total usage vs base), payback, etc. There’s a notable blip in Jul ’13 when we went from 5 to 12 panels, with each calendar year change as we “net out” and either add or subtract the annual bill or credit into the equation and add in any pricing changes in the “SCE $/kWh” column. I dropped a copy into my Dropbox public folder if anyone wants to find all my errors/reapply/make it your own (link).


What a whirlwind of data. Now that your head is spinning with numbers, take a break, grab some coffee, and come back in 5.

We’ve determined what your usage is for the year, adjusted for all the great efficiency improvements you’re going to make with your tax returns (right?), sized the system based on your specific location, and worked through the financial side of the system. What now? Let’s throw an EV into the mix! Put some miles on those solar panels! But seriously, how do you figure out how much power you’ll need to get back and forth to work? Come with me, friend…

When buying an EV, you enter a new world of numbers and metrics. Nobody will tell you the most important factor in calculating your energy usage, but it’s simple — miles per kwh. Basically, how far you can drive on one unit of electricity. Boiling it down to the basics, your EV has a certain battery size — say 24 kWh — and gets a certain range — like 84 miles. Roll those two together and you get the manufacturer’s estimated miles/kWh rating. In this case, that’s 84/24 or 3.5 mi/kWh for my 2014 Nissan Leaf. I must have a light foot because I have averaged 4.1–4.3 mi/kWh since we’ve had it… which also means I get more miles out of a charge, which is nice.

Now that we know how efficient your EV (or EV-to-be) is, just roll that into the number of miles you drive per year or plan to drive in the years ahead to get your EV’s annual kWh usage. You can run this through the same usage-to-system-size calculation to determine what size PV system you need to power your car. In my case, I used the actual production averages from my panels to calculate this at a “high” miles per year number (12,000) and a “low” miles per year number (8,000) to understand what those thresholds looked like, then sized accordingly.

Our Leaf Charging in a Santa Monica, CA Parking Structure FREE!

Tracking solar generation allows us to understand our system payback vs retail pricing, aka “what you would have paid for the power” — or the cost of the solar system per month. Keeping a running total of the savings allows you to estimate payback time for the system, at which point the system is effectively producing free power. Tossing an EV into the mix, I track EV savings as :

[miles driven / mpg of the car we replaced * price of gas for the month (actuals)]


[miles driven / (mi/kwh of the car) * retail cost of electricity/kWh]

Or… in simple terms, the amount of money we would have spent on gas minus the money we would have spent on electricity = savings from the EV vs a gasmobile.

Solar-powered charging at home is the most cost-effective, environmentally friendly form of vehicle-based transport that fits our lives (today). After we added the first EV in late 2014, we decided to go all-in and added a second EV just a few months ago. We are currently saving money on our electricity bill with the 17 solar panels we have up on the roof, with another 10 panels that we’ve already purchased that are currently waiting for a home electrical panel before we can add those to get back to a state where we are producing more power than we use. The second EV put us back “into the red” but also gets us off gas, which is a bigger win in my book. :)