Net Zero mission accomplished

One of my major goals for our home renovations has been achieving Net Zero, meaning our house produces as much energy as it consumes. As one might expect, producing as much energy as we consume yields energy bills of less than $0.  Today I consulted my energy meter and extracted the following data points for calendar year 2017:

  • Energy Produced: 9,288 kWh
  • Energy Consumed: 12,396 kWh
  • Energy Consumed by Auto: 3,216 kWh
  • Energy Consumed by Building: 9,180 kWh

For the purposes of measuring building consumption, I subtracted the auto consumption (measured by our chargepoint home charger) from total consumption. Since our building produced 108 kWh more than it consumed, I can claim the Net Zero goal as accomplished.

Our home and EV together consumed 1,500 kWh less in 2017 than 2016. Looking forward, I anticipate a similar reduction in 2018 because we were using space heaters for part of the house in Jan-Apr of 2017. The heat pump for that area is now installed. Also, the concrete basement and downstairs walls aren’t insulated yet. I have the insulation (XPS & poly-iso) standing by and it will be installed before the next heating season.

I don’t expect an substantial efficiency improvements after 2018. All our energy systems are super efficient, our insulation levels are super, and our energy surpluses (say hello to Energy Plus) will be consumed by our current and future EVs. Any further efficiency improvements would have no economic justification.

Reference points

  • Average home energy consumption: 23,000 kWh
  • Average auto energy consumption: 15,000 kWh
  • A super-insulated (aka: ultra efficient) home typically needs 1/5 the energy for HVAC.
  • On average, EVs consume  1/3 the energy of an ICE vehicle.

Is A Powerwall Worth It?

Primarily for economic reasons, I covered our roof with 10kW of solar panels. As a producer of electricity, it no longer made sense to pay a utility company for natural gas so the furnace was replaced with heat pumps and the water heater was replaced with a HPWH. The fireplace and chimney were anachronisms I was happy to get rid of. I removed all the gas lines and had PSE remove the leaky gas meter as well. From a safety perspective, ridding our home of combustion appliances was a big win.

While on the topic of safety, the Big One is coming. Our home was built in 1955, way before the Nisqually Quake and updated building codes. I’ve done a few seismic retrofits as suggested by the City. The most important thing, literally, is surviving the quake, so making sure our house doesn’t collapse is a good start. The next most important thing is potable drinking water. I warehouse a weeks worth. For lighting we have camping headlamps, Mr. Beam night lights around the house (with rechargeable AA batteries that last about a month) and outside, I’ve got solar LED lights attached to the house. They’re really nice when walking around the house at night and would suffice during a power outage.

What I don’t have is energy storage. For the safety of linemen, when the grid is down, so is my array. I want a Tesla Powerwall so I can operate off grid. For $6k, Tesla provides a 14kW battery and the transfer switch that enables off grid operation. In the summer, our array produces double what we use (including EV charging) so a single Powerwall could easily power our house, plus extension cords to the neighbors for their fridges, indefinitely. In mid-winter, with no visible sun and freezing temps we could drain a Powerwall in just two days. But after a winter disaster, we could turn the heat off, dress warm, and power the house for weeks. Or heat just one room. That’s a compelling use case, but I have yet to conclude that the potential losses from not having a battery (spoiled food, no lights, no cooking, no heat) during an outage outweigh the $6,200 price tag.

Solar ROI update

I now have a full year of electric production and consumption measured. I also have the SCL rate updates for 2017 and 2018 so I have updated my solar ROI estimates. The significant change is that the Net Metering benefit has substantially increased due to:

  1. SCL electric rates are higher in Shoreline than Seattle.
  2. The 2017 and 2018 rate increases are 5.6% (estimated at 4%)
  3. An added RSA surcharge of 1.5%
  4. The coldest winter in 32 years
  5. More electricity use than I predicted.
    • I was still insulating deep into the heating season.
    • I guesstimated the kWh it would require to heat a 1955 house with heat pumps.
    • I installed a fast (level 2) charger for our Leaf. We were able to use it more, offsetting gasoline with electricity.
  6. The increased usage is all at the higher 0.14¢ price tier.

Reasons 1-4 weren’t known during my initial estimates. Reasons 5 and 6 were planned but their scale was unknown. I knew I’d be removing all natural gas appliances (furnace, water heater, fireplace) but I hadn’t yet decided whether to install tankless electric or a heat pump water heater. I hadn’t chosen the heat pumps for house heat yet so I didn’t know their HSPF. I also didn’t know how much more we’d be able to use the Leaf.

The net result is that I now estimate a 100% return on the solar array in the 6th year instead of the 8th year.

Notes

  • I did not include the cost of the heat pumps or the heat pump water heater. Those were efficiency upgrades that I’d have done anyway. If I were keeping natural gas, I’d have replaced the old 80% furnace with a 97% modulating furnace and the “well past its expected lifespan” gas water heater with a gas tankless. In both cases the costs are comparable and just like replacing the fridge, the efficiency increases have their own ROI schedule.

Solar 11-month update

On a typical “it rained every single day in April” month, we still managed to skate across the finish line at nearly at Net Zero:

April 2017 household energy
April 2017 household + auto energy budget

Last year I removed all the natural gas appliances and converted everything to electric heat pumps. I sized the 10kW array aiming for Net Zero during the calendar year. That would mean producing enough surplus during the summer to carry us through the winter. It looks like we’re going to miss this year:

2016-2017 household energy budget

Even though we’ll be banking surpluses in May, it won’t close that 7MWh deficit. Our household usage includes over 3MWh of car charging and this last winter was Seattle’s coldest in 32 years. The heat pumps were working overtime to keep the house warm.

Apple data centers on 100% renewable power

Apple is spending an eye popping $850 million to build a ginormous solar farm (280 megawatts) that will power their entire California operations. This new solar farm is not to be confused with the 70MW solar farm they’re building in Arizona, the $55 million “under way” third solar farm (17.5MW) in North Carolina, the two 20MW solar farms they’re building in China, or the existing 20MW solar farm near Reno, NV, or the two existing 20MW solar farms in N. Carolina.

The backstory is that in 2010, Apple wanted to buy renewable energy from Duke to power their Maiden N.C. data center. It wasn’t even legal in N. Carolina. In 2011 Apple bypassed the N.C. coal lobby by purchasing 100 acres of land and in 2012 they finished building (est. $100 million) the first non-utility 20MW solar farm. At the same time, they also built a 5MW fuel cell farm. In 2013 they doubled their fuel cell farm to 10MW and built another 20MW solar farm. Apple has since been producing 100% of the power they need in N.C.

While I believe that Tim Cook is sincere about reducing Apple’s carbon footprint, I also think it’s likely that spending over a billion dollars on solar panels is a very good investment. Apple is famously cash rich and by spending today and owning the solar farms, Apple fixes their energy prices at today’s rates for the next 30 years. Apple has taken a large and variable cost and turned it into a fixed cost that is no longer subject to price inflation or fluctuation. What Apple is also purchasing is energy stability.

Apple is also becoming an energy supplier. For the first 10 years, PG&E will purchase 150MW of production and Apple gets 130MW.  In the last 20 years, Apple gets 100% of production. It’s likely that their operations will have expanded to utilize the power (as has the NC data center) but if not, they’ll have little trouble selling their surplus capacity.

While Apple was first in the, “okay then, we’ll build it ourselves” solar game, the even bigger story is that 2014 was the year solar arrived in Main Street USA. In just 2014, nearly 70% of the worlds solar power generation came online with several companies having more installed solar than Apple: Wal-Mart (105MW), Kohl’s (50MW), and Costco (48MW). IKEA is not far behind with 39MW. Apple isn’t even the largest purchaser of solar as Intel, Kohl’s, Whole Foods, Dell, and Johnson & Johnson all purchase more solar power than Apple. What was so special about solar in 2014?

Swanson’s Law observes that solar modules tend to drop in price by 20% for every doubling of cumulative shipped volume. Apple deployed 60MW between 2012-2014 and during that same time, photo voltaic capacity more than doubled. By being out in front and building not just demand, but also solar capacity, Apple helped 2014 be the year of solar grid parity in 3 NE states, California, Arizona, and Hawaii. It is predicted that grid parity will arrive in “many” US markets in 2015 and Deutsche Bank predicts solar grid parity for all 50 states in 2016. With Apple deploying another 407MW of solar In just 2015-2016, that prediction seems like slam dunk.