The Myth of Whole House Battery Backup

The Myth of Whole House Battery Backup

Will batteries keep your AC cranking and electric vehicle charged up during an extended blackout? Probably not.

We like to believe the myth of whole house battery backup or the notion that our 21st century lifestyle will continue unabated despite fire hell or high water. The reality is different: Typical battery backup systems work best when they are designed to ration battery capacity and minimize the use of major appliances. These systems must also be integrated with rooftop solar so that the battery can be recharged as soon as the sun comes up.

There are two fundamental engineering limits that make it impractical to run a whole house on battery power alone. First, the energy capacity of typical lithium-ion battery systems is insufficient to power an entire house through a nighttime blackout. Second, battery backup inverters are not powerful enough to start and run many large appliances. Adding multiple batteries and inverters can overcome these engineering limits – but at a very high cost.

Nevertheless, a well-designed solar and whole house battery backup system can provide limited power almost indefinitely. To learn more about the reality of backup power in the event of a blackout or Public Safety Power Shutoff, please listen to this week’s Energy Show.

SolarEdge-Perspective for a Distributed Grid

SolarEdge-Perspective for a Distributed Grid


People talk about solar panels and batteries a lot (at least the people I talk to). The reasons are that solar panels are conspicuous on rooftops — and batteries are what keep the lights on during increasingly frequent blackouts. But the real brains of a solar and battery storage system is the inverter.

With increased global production, solar panels and battery cells have become commodities — differentiated mainly by price and efficiency. For a variety of reasons, inverters are still quite specialized. Initially, inverters simply converted DC current to household AC current. Modern inverters also provide a variety of safety features (rapid shutdown and arc fault protection), monitoring, and grid support services. The next generation of inverters extends beyond solar, providing backup power, EV charging and home energy management capabilities.

Through a combination of great technology, disciplined execution and industry vision, SolarEdge has become the leading inverter company. Based on my experience in the field (and roof), they have the best combination of efficiency, safety, installation ease and overall value. Most importantly, SolarEdge continues to push the technology envelope as they expand into backup power and distributed grid services.

Our guest on this week’s Energy Show is Peter Mathews, General Manager of North America for SolarEdge. He has done a terrific job growing SolarEdge to over a 60% market share in the U.S. Please listen to this week’s Energy Show as Peter shares insights around SolarEdge’s business, how SolarEdge is addressing the power crisis in California, their new commercial products, and the company’s ongoing product vision for a distributed grid.

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.

What’s a Watt – Energy & Power Explained

What’s a Watt – Energy & Power Explained

On this week’s The Energy Show, we’re talking about energy — duh. And power. Not just because we’re short on both energy and power. But because solar and battery customers need to understand these properties so they can properly size and operate their systems. This show is a bit on the geeky side, so buckle up.

Power is the measure of the amount of work that can get done over a period of time. We measure power in units of watts in the metric system, and in units of horsepower in the English system. Even though the English use the metric system and horses are basically just recreational vehicles for rich people. Commonly we refer to the power of a car in horsepower, or the power requirements of an appliance in watts.

Energy is the measurement of work, or force over distance, or an amount of heat. Not a watt, but instead a watt hour or kilowatt hour (kwh). Your utility bills you for electrical energy in terms of kilowatt hours, and for natural gas thermal energy in terms of Therms (geeky rhyme). A Therm is 100,000 BTUs, which stand for British Thermal Units — which is a measure of energy in the English system — which only the Americans still use (my high school English teacher would have referred to this sentence as a which hunt).

In the solar world, we measure the power output of a solar panel in watts (360 watts per solar panel under ideal conditions), or the total size of a 20 panel system as 7,200 watts. Home battery storage systems are measured in terms of kwh (most commonly a 10 kwh or 13.5 kwh battery), and commercial systems are measured in terms of mwh (megawatt hours).

Feel free to download this week’s Energy Show for more information about the energy and power terms we use in the solar and storage industry to measure size and performance of solar and battery storage systems.

DOE Continues Solar & Storage Progress

DOE Continues Solar & Storage Progress

In today’s accelerated and politicized news cycle it is easy to confuse White House pronouncements with the policies that government employees are actually implementing. The U.S. has about two million hard working government employees (disparagingly referred to as the “deep state”) who are dedicated to their jobs and following well-established laws and policies.

There is perhaps no better example of this dedication and progress than the 100,000 people at the Department of Energy (DOE). Although based on recent events I would say EPA employees are in the running for the hardest working and politically least recognized branch of our government. But I digress.

As a result of long established policies and investments, the U.S. is continuing its worldwide leadership in energy and efficiency technology. Although we could obviously be doing a lot more on many dimensions, it is not complete gloom and doom. Once new energy technologies prove they are better and cheaper, no amount of political backsliding can bring back the old ways of doing things. We are no more likely to resort to heating our homes and offices with wood than we are to replace LED bulbs with short-lived, hot and energy-wasting incandescent light bulbs (regardless of the affects they may have on our complexion).

For 2019 Congress authorized $35 billion in funding to the DOE – more than the $30 billion the President recommended. This $35 billion will be spent as follows:

  • $15b for the National Nuclear Security Administration — basically for weapons and cleanup from past nuclear programs (almost half of the DOE’s budget)
  • $7.2b for environmental management
  • $6.6b for pure science
  • $5b for energy programs – of which $2.5b is for energy efficiency and renewable energy, $1.3b for nuclear energy research, $1b for fossil fuel research and the rest for miscellaneous programs.

The good news is that the DOE is continuing great research into a broad range of renewable energy technologies. The even better news is that there are almost a hundred thousand people hard at work at the DOE striving to make solar, storage and newer technologies better and cheaper – regardless of temporary political headwinds. To learn more about the work being done by the committed people at the DOE, please tune in to this week’s Energy Show.

Reducing Peak Demand Charges

Reducing Peak Demand Charges

Unless you have rooftop solar, you’re probably incredibly unhappy about rising electric bills. This misery is even worse for commercial customers since — in addition to energy charges (billed on a kilowatt-hour basis) — they also pay for peak demand charges (billed on the maximum kilowatt demand each month).

For example, let’s say your business uses industrial equipment and a variety of office equipment. Your company uses 50,000 kwh of energy per month; at a rate of $0.15/kwh, your electric bill is $7,500 per month. In addition, your peak demand may be 300 kilowatts in a typical month; at a peak demand rate of $20 per kilowatt, you also pay $6,000 in demand charges every month.

As a conscientious and generous employer, you decide to install 20 EV chargers in your parking lot so your employees can charge up their cars while at work. Each employee may charge up their car with about 10 kwh per day — or $1.50 worth of electricity each, or $600 for all employees each month. A nice employee perk, and not too expensive. However, since 20 employees plug in their cars at about the same time every morning, and each charger draws about 5kw, your extra electricity peak demand will be 100 kw, or an extra $2,000 per month. Ouch!

So for many commercial customers, peak demand charges are a bigger cost than energy charges. Ordinary rooftop solar systems may not have a big impact on demand charges. However, batteries or special control systems in conjunction with rooftop solar can significantly reduce these demand charges.

To learn how your company can reduce peak demand charges, listen to this week’s Energy Show as we speak with John Powers with Extensible Energy. Extensible Energy has software that helps commercial solar buildings to use electricity intelligently and reduce peak demand charges.