Converting a House to Zero Net Energy

Converting a House to Zero Net Energy

Buildings consume 40% of our energy, most of that for heating and cooling. Almost all of this energy is supplied by fossil fuels, resulting in tremendous CO2 emissions. Building electrification solves this problem. Instead of burning fossil fuels in homes and businesses, we can heat, cool, wash and cook using electricity generated from clean, renewable sources.

San Jose is one of the first cities to establish building codes that pursue a  zero net energy policy by strongly recommending all electric new homes. But what about existing homes? To find out first hand what was involved in getting to a zero net energy home, my wife and I embarked on a project to completely electrify our 50 year old home in San Jose.

I’ve done quite of bit of energy upgrading on homes and businesses over the past 40 years. Nevertheless, I checked in with a few friends who had done some electrification of their homes (thanks to Howard, Jeff and Dick). The steps we took mostly followed conventional wisdom: address the easy and cheap items first (LED lights, controls), extra insulation, solar with battery backup, EV charger, heat pump HVAC, heat pump water heater and induction cooktop.

There were only two real hassles with this electrification project. The first hassle is familiar to anyone doing a renovation or maintenance project: finding the “best” contractor for each individual task. Because building electrification involves so many different types of contractors, there is no one “general contractor” who can do everything both efficiently and cost effectively. We ended up with five different contractors: insulation, pool, solar, electrical and HVAC. Since I’m capable of screwing in a lightbulb, I took care of the LEDs lights and controls. The biggest hassle was on the electrical permitting side and coordinating with our local utility. Nevertheless, when everything was done and connected, we are enjoying a net negative (for the year) electric bill — including all of our heating, cooling, cooking and most of our driving.

Perhaps the most rewarding event was when our local gas utility PG&E sent an inspector to our house to find out why the gas meter almost stopped completely! To learn more about electrifying your home or business, please listen to this week’s Energy Show. And if you are thinking about making the switch from fossil fuel home appliances to electrical appliances run by solar and battery storage solutions, take a look at our 10 steps to whole house electrification.

Solar Tracker Systems with Alex Au

Solar Tracker Systems with Alex Au

Whether it’s a residential, commercial or utility solar project, contractors strive to install systems that generate the most energy at the lowest lifecycle cost. Solar panels operate at their peak output when the sun is perpendicular to the panel. So for maximum energy collection, tilting the solar panels at the local latitude (37 degrees here in San Jose) facing south is generally best.

Because of existing building structures, compromises are necessary when installing solar panels. Residential systems are generally installed flush to the roof because tilting the panels is unsightly, and the efficiency benefit of tilting the panels is not worth the additional mounting system costs. Commercial systems on flat roofs are generally installed on racking at a relatively low tilt so that more panels can be installed — but almost never horizontal since flat surfaces collect dirt and debris.

But large-scale solar installations do not need to compromise when it comes to tilt angle and orientation. Systems can be more easily oriented due south and tilted at the angle of the local latitude. Taking things one step further, since the sun moves throughout the day, an additional 10-25% efficiency can be achieved if the panels track the sun.

Single axis solar tracker systems generally towards the east in the morning and west in the afternoon. More complicated dual axis solar tracker systems tilt east-west daily and adjust north-south seasonally. Because of the increase in efficiency, trackers have become a standard feature on large solar farms. Essentially, the added complexity of moving parts is worth the big increase in energy output.

NEXTracker was recently ranked the number one tracker company globally. They provide tracking systems and engineering for large utility scale projects all over the world. My guest on this week’s Energy Show is Alex Au, CTO and co-founder of NEXTracker. Alex was one of the pioneers in the solar industry as a key member of the team that developed the first integrated racking AC solar module, and then developed NEXTracker’s core tracking technology.

Please listen up to this week’s Energy Show as Alex shares his insights on NEXTracker, their technology and their recent work in incorporating flow battery technology to help eliminate the imbalance between peak demand and renewable energy production for utility scale applications.

Which Solar Panels Should I Buy?

Which Solar Panels Should I Buy?

The most common questions that prospective solar customers ask is “Which solar panels should I buy?” That’s a tough question to answer, and arguably maybe not the most important question (more about that later).

I initially got into the solar business for altruistic reasons — save the planet and all that. The planet still needs saving, perhaps more than ever. But I quickly realized that the vast majority of customers were interested in saving money first (the planet could wait). So I am biased towards finding the most cost-effective system for customers. To that end, people want an inexpensive system that is reliable, high efficiency (especially if they have limited roof space), and looks good on their roof.

When it comes to the solar panels themselves (also called solar modules), all solar panels generate the same amount of electricity on a per watt basis. A 300 watt panel from Manufacturer A will generate the same amount of energy as a 300 watt panel from Manufacturer B. 24 panels with a 275 watt output will generate the same amount of energy as 22 panels with a 300 watt output (6,600 watts). Your appliances can’t tell the difference if they are using electrons from a super high efficiency panel or from a less expensive system. Nevertheless, there are clear cut differences among solar panels in terms of efficiency, aesthetics, cost and availability. On the other hand, some of the sales pitch distinctions are subjective, such as brand, quality, durability, and long term energy output.  

To learn more about critical decision factors in purchasing solar panels for your home or business, listen to this week’s Energy Show. For those of you who have read to the end of this summary, the most important question to ask is: “which contractor will install the best solar power system for my home or business?”

Weather Impacts on Solar Power Systems

Weather Impacts on Solar Power Systems

This past winter season has been the rainiest I have ever experienced in California. The good news is that the state is no longer in a drought condition. The bad news is that severe weather is occurring around the country. We are likely to continue on this trend: a polar vortex recently hit the Midwest, heavy snows on the east coast, and even Seattle was devastated with big snow storms. 2018 was the 4th hottest year on record globally. On average, the summers are getting hotter and the winters are not as cold. 

But this is a show about energy — particularly solar. Although the output of solar systems can be predicted fairly accurately, weather has the biggest impact on annual energy fluctuations [side note: the biggest monetary fluctuations come from your local utility as they raise electric rates]. Several of our customers were concerned about lower energy output from their solar system in November, December and January. We pointed out that rainy weather — including smoke from wildfires — obscured the sunlight enough to make a noticeable difference in energy output. Even our customers who had battery backup systems contacted us, but for different reasons. Many of them had multiple weather-related blackouts this winter. These customers were delighted that their refrigerators, TVs, lights and heat were all still working even though their power was out. 

While one cannot change the weather (unless your name is Dr. Evil), we can prepare for a changing climate. Please listen up to this week’s Energy Show as we discuss how weather impacts solar power system performance.

Cleaning Solar Panels

Cleaning Solar Panels

When a business or homeowner gets a new rooftop solar installation, the second question they always ask is “how often do I need to clean my solar panels.” We’ll answer that question on this week’s show — taking into account the different effects of rain, dust and electric rates. BTW, the first question people always ask is “how do I read my electric bill;” but that’s a topic for another show. (more…)

The Commercial Solar Opportunity

The Commercial Solar Opportunity

There are there are three market segment for solar in the U.S.: residential, utility and commercial. Based on some rough math, in 2018 we expect to install 5 to 7 million solar panels on homes in the U.S. In areas with high residential electric rates, paybacks are usually in the range of 4-8 years. But the utility solar segment is much larger: about 20 million solar panels will be installed by utilities in 2018. Utilities realize that it is cheaper to generate power with solar compared to coal or nuclear generation. Moreover, the combination of solar and batteries is projected to be even cheaper than natural gas in a few years. (more…)