To slow the global warming trend, a number of states have committed to the aspirational goal of 100% carbon-free energy. As a species that literally evolved from burning wood and hydrocarbons, how can we possibly run our modern lives and economy without fossil fuels?
We can indeed achieve this transition quickly and economically. First, by converting all power generation to renewable, non-carbon sources. And second, by converting all fossil-fuel burning vehicles and appliances to electricity. Steady progress towards these conversions is being made. For example, 32% of California’s retail power came from renewable energy in 2018. The state is well on the way to converting to 100% renewable electricity. Use of EVs is growing steadily, and new building codes mandate the use of rooftop solar and electric appliances instead of natural gas.
The challenge is with the existing stock of residential and commercial buildings. Homes and businesses predominantly use natural gas for space heating, hot water heating and cooking. That’s where the concept of Whole House Electrification come in. Whole House Electrification is conceptually simple: replace gas appliances with electric appliances. In reality, one needs an energy audit to prioritize these conversions, then hire five different specialty contractors to do the work: insulation, solar, HVAC, plumbing, electrical and pool. It can be a daunting task.
Fortunately there are some pioneers out there – one of whom is my friend Howard Wenger. Howard was also a pioneer in the solar industry, with stints at AstroPower, PowerLight and SunPower. Please listen up to this week’s Energy Show as Howard discusses his experiences as he converted his house to 100% electricity, supplied — naturally — by solar.
We’re talking about hot water this week. No — I’m not in trouble with my local utility again — just discussing the best ways to heat water for your home. Our focus is on domestic hot water (DHW). This is hot water that you use for your kitchen, bathing and laundry. In the U.S., the average home uses about 68 gallons of hot water a day, with huge variations based on the number and age of occupants in the home. (more…)
There’s no doubt in my mind that the home of the future will be solar powered. Intuitively it would be great if the roofing material provided that solar power. But historically it’s been a challenge to combine efficient solar cells with a durable roofing material at an affordable price. Tesla’s new solar roof tiles hope to solve these challenges.
Without a doubt Tesla’s solar tiles are the best looking solar roofing products I have seen. Using Tesla’s solar roof tile calculator and information for a 2,000 square foot home in California with a 2,500 square foot roof and $200 monthly electric bill, here is how their solar roof tiles compare to an ordinary rooftop solar panel installation:
Tesla Roof Tiles
Ordinary Solar Panels
Up front cost
Simple payback (years)
Of course I expect the cost for Tesla roof solar tile installations to come down in the future, so their economics are likely to improve. Nevertheless, at these high prices it is clear to me that Tesla really has a product that only makes sense for new construction on high end homes. For the average homeowner considering solar, by far the best choice is a traditional rooftop solar power system. For more about Tesla’s solar roof tiles, Listen Up to this week’s Energy Show on Renewable Energy World.
When someone 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).
Rooftop solar panels get dirty primarily from wind-blown dust and pollen. Birds are usually not a problem unless your last name is Hitchcock and you live in Bodega Bay. As panels get dirtier, their output declines. A small amount of soiling — say a light dusty film — may only cause a 5 percent output decline. However, when panels get very dirty — perhaps in an agricultural area or location that does not get regular rainfall — the output decline can be greater than 20 percent. A good heavy rainstorm will usually wash away most of the accumulated soiling.
I use the term “usually” because on panels that are tilted at about 5 degrees or less, the rain may leave a puddle of muddy debris along the lower edge of the panel. When this puddle dries, sometimes a thick layer of dirt accumulates along the lower row of cells (sometimes moss and weeds may even grow in these areas). Depending on the design of the system, this small accumulation of dirt can cause a very significant decrease in output.
So the answer to the question: “how often should I clean my solar panels” really depends on five factors: your location (does it rain regularly or only during certain months), the tilt angle of your panels (steeply tilted panels tend to stay much cleaner than panels that are close to horizontal), the amount of wind blown dust, your electric rate (if your electric rate is high then it is more worthwhile to clean your panels), and the cost to clean your panels. For more about cleaning your solar panels, please Listen Up to this week’s edition of the Energy Show on Renewable Energy World.
Almost all solar panels sold in the U.S. carry a 25 year warranty, most inverters are guaranteed for 10 to 25 years, and as long as you get occasional heavy rain your panels do not need regular cleaning. So if you are thinking about solar for your home, the most important considerations – besides price – are the quality and reliability of the installation itself. With these factors in mind, here are my top ten tips for 25 years of trouble free solar power:
Find an installer who has been in business for 5+ years and uses their own installation crews (not subcontractors).
You get what you pay for – so be careful about selecting an installer based on the lowest price.
Prices for battery storage systems are coming down fast, storage incentives in many states will be available soon, control software is being developed, and the reliability of this new technology is improving rapidly. My advice is to get a battery-storage ready system, while waiting for these improvements to settle down in the market over the next few years.
Panels from the major manufacturers are all very reliable; the biggest difference is simply that higher efficiency panels cost more. In most cases it does not make sense to pay extra for highest efficiency panels if you have enough roof space for slightly lower efficiency panels.
The most common customer service issue relates to inverter monitoring. A distant second is a problem with the inverter itself.
Squirrels and rats like to nest under rooftop panels and chew wires. Pigeons prefer barrel tile roofs. If you have any of these pests on your roof, talk to your installer about installing screening around the perimeter of your panels.
Make sure your installer uses the proper flashing and sealing techniques on your roof mounts. Flashings are mandatory on all composition shingle roofs.
Heavy rain does a great job of cleaning off debris from rooftop panels. NEVER hose off your panels – mineral deposits from tap water can permanently damage the glass.
Wiring should be securely tucked-up beneath the panels and racking. Contact your installer if there are any wires hanging down on the roof surface.
To make sure your system is operating properly, keep an eye on your inverter display (or online display), as well as your monthly electric bill. Even if your installer is monitoring your system they might not always notify you if there is a problem – especially if there is a problem with your monitoring.
For details on these ten tips for 25 years of trouble-free rooftop solar, Listen Up to this week’s Energy Show on Renewable Energy World.
It may seem counter-intuitive, but you can have too many solar panels on your roof. With conventional net metering, your utility will not reimburse you at the end of the year if you produce more power than you consume. For example, last year my electric bill was -$46.86. Our roof has a 6kw solar system on it, but because we installed a new thermostat, LEDs and new windows, we generated a net credit with our utility last year. So I’m replacing my LEDs with old-fashioned incandescent light bulbs so I can use more power and get closer to a zero bill this year. The number of panels you need is based on two factors: the available space on your roof and the size of your electric bill.
A good installer will not take advantage of you by installing modules where there is a lot of shade or a poor north-facing orientation on a steep roof. Along the same lines, your installer should analyze your current electric bill and recommend the number of solar panels that will get you close to a zero bill.
Once you know these two boundary conditions – the number of panels that fit on your roof and the number of panels that you need to zero out your bill – you can see what size system fits in with your budget and method of financing. At the same time your installer should step you through the options for different levels of solar panel efficiency, module electronics (optimizers or microinverters), and changes in your future use of electricity (such as an EV or energy conservation measures). For more about determining the optimum size of your solar power system, Listen Up to this week’s episode of The Energy Show on Renewable Energy World.
Barry Cinnamon has been blogging about the Solar Industry since 2007.
Barry hosts The Energy Show, a weekly 30 minute talk show that runs every Saturday at 1:30 PM on KDOW Radio AM in San Jose California.
Every week Barry provides practical money-saving tips on ways to reduce your home and business energy consumption.
Barry Cinnamon heads up Cinnamon Energy Systems (a San Jose residential and commercial solar and energy storage contractor) and Spice Solar (suppliers of built-in solar racking technology). After 10,000+ installations at Akeena Solar and Westinghouse Solar, he’s developed a pretty good perspective on the real-world economics of rooftop solar — as well as the best products and services for homeowners, manufacturers and installers. His rooftop tinkering led to the development of integrated racking (released in 2007), AC solar modules (released in 2009), and Spice Solar (the fastest way to install rooftop solar modules).
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