According to Doc Brown, Marty McFly’s DeLorean needed 1.21 gigawatts to travel back in time. To put this in perspective, new gas power plants are about 0.5 gigawatts, typical large utility scale solar power plants are 0.1 gigawatts, and the average rooftop solar system is 0.000005 gigawatts (5,000 watts). Although it takes a lot of solar panels to generate the power our society needs, solar is now one of the cheapest and cleanest sources. And “clean and cheap” is now the world’s preferred power source: in 2013 the world added 143 gigawatts of new renewable energy generating capacity compared to 141 in new plants that burn coal, natural gas, or oil.

Fossil fueled power plants have not just taken a temporary back seat to renewables - we are witnessing a long term transition in the world’s energy sources. The price of wind and solar power is on par or less than fossil fuel electricity. Renewable energy prices are on a steady pace to get cheaper, while gas and oil will inevitably go up as supplies are constrained and climate change effects are considered. Coal plants are being decommissioned, and new nuclear plants are effectively doomed -- it took 36 years from start to finish for the last nuclear plant to come on line. Compare that to 45 days for a new solar power plant on your home’s roof, or three years for a utility-scale solar project.

Utilities are installing solar power plants to generate electricity for their customers because solar is cheaper. But this change in our energy sources will take many years, just as the complete transition from “horse and buggy” transportation to gas-powered cars took 50 years. As with other large-scale technological changes, customer economics will force the current incumbent energy providers to change (unlikely), or go out of business (more likely). It’s a virtuous cycle as more customers are satisfied with renewable power generation, and more people are employed in these industries. For more on this inexorable, economics-driven transition to a clean energy economy.

I’ve spent a lot of time over the past 15 years talking to homeowners about rooftop solar. More kitchen table chats and walks around the house than I can count. Some of the basic questions I hear again and again. Because they are new to solar, some of the most important questions do not even occur to homeowners.

On this week’s Energy Show we’re going to address some of the more obscure questions that homeowners should ask... and installers should be prepared to answer:

Why do I need a building permit for solar?

What happens if I run my electric meter backwards and don’t tell my utility?

Can I use the power from my solar system during a blackout?

Who covers the warranty on my solar installation and solar equipment?

Is 3% or 4% or 5% a reasonable projection for electric rate escalation?

If I sell my house, how will the new buyer value my solar installation?

Will that tree to the south of my roof shade the system and reduce its output?

Do I need to clean my solar panels?

Is there a catch with a “no money down” deal?

How much will I save with my solar system?

I had a little roof leak last year? Is it OK to put solar panels on my roof?

We’re talking about religion this week. Did I get your attention? How about if we talk about climate change, more renewable energy, dirty fossil fuels and solar subsidies? OK, we’ve already covered these topics. But now the Pope has chimed in with his “On Care For Our Common Home” Encyclical. I’m probably the worst person to comment (I got kicked out of Hebrew School). But I did read all 180+ pages of his Encyclical. There is no doubt in my mind that the Pope’s analysis and commentary will definitely affect U.S. politics related to clean energy.

First, the Pope describes the problem succinctly: pollution and climate change. Some quotes:

“Very solid scientific consensus indicates that we are presently witnessing a disturbing warming of the climatic system."

“Problem is aggravated by a model of development based on the intensive use of fossil fuels."

“Urgent need to develop policies so that, in the next few years, the emission of carbon dioxide and other highly polluting gases can be drastically reduced, for example, substituting for fossil fuels and developing sources of renewable energy."

“Economic interests easily end up trumping the common good and manipulating information so that their own plans will not be affected (greenwashing)."

"Whereas any genuine attempt by groups within society to introduce change is viewed as a nuisance based on romantic illusions or an obstacle to be circumvented (those pesky Climate Change nuts)."

He then continues with solutions that are both practical and grounded in economics:

"We know that technology based on the use of highly polluting fossil fuels – especially coal, but also oil and, to a lesser degree, gas – needs to be progressively replaced without delay."

"Until greater progress is made in developing widely accessible sources of renewable energy, it is legitimate to choose the lesser of two evils or to find short-term solutions (natural gas as a temporary bridge)."

"Taking advantage of abundant solar energy will require the establishment of mechanisms and subsidies … The costs of this would be low, compared to the risks of climate change (renewable energy incentives)."

So what does this all mean? Clean energy supporters and environmentalists are happy to have the Pope on their side. Dirty energy proponents and climate deniers have to argue against the formalized position of the Catholic church...I’m sure the Koch brothers aren’t happy. Right wing Catholic politicians have to choose between agreeing with the Pope -- or accepting fossil fuel campaign money.

Overall, this Encyclical — and subsequent Papal speeches — will gradually dissolve the political right-left gridlock on climate change and the actions necessary to mitigate it. I am particularly looking forward to the Pope’s address before Congress in September (ironically, the Pope was invited by Speaker of the House Boehner). So please Listen Up to this week’s Solar Energy Show for more details on the Pope’s Encyclical and its positive impact on the continued growth of renewable energy throughout the world.

Things have been changing pretty quickly in the light bulb business. In the course of a few short years, Edison’s filament bulbs have become illegal, marginally more efficient halogen bulbs have become the default choice in hardware stores, twisty compact fluorescents (CFL) have pretty much had their day in the sun, and specialty LED bulbs are now inexpensive and available in virtually every shape, size and color.

When I researched residential lighting a few years ago my conclusion was to go with CFLs because they had the lowest operating costs - but you had to tolerate their slow start up and poor colors. Since then LED bulbs have plummeted in price. Moreover, one can buy LEDs that fit virtually every fixture and claim to work in dimmers. So now it’s almost a no-brainer to go with LEDs.

Nevertheless, there are still challenges with LED bulbs. Although they all indicate a 22.6 year lifespan, I have had a number of them burn out already. Not all are as dimmable as they claim. Some of the bulbs are too bulky or weirdly shaped to fit in existing features. And the color of the light is sometimes not as warm as conventional bulbs (which are no longer available). Please Listen Up to this Week’s Energy Show on Renewable Energy World as we survey the real-world advantages and disadvantages of the current crop of LED bulbs.

Water from Desalinization by Barry Cinnamon

The sun is shining brightly on your rooftop solar panels (or the panels you hope to have). But how can you tell if those photons falling from the sky are actually turning into useful electricity? Since there are no moving parts to a rooftop solar system, it can indeed be difficult to tell if you are getting what you paid for. Fortunately, there are four easy ways to keep an eye on your system’s performance. Check the green light on your inverter, check to see that your meter is running backwards, check your electric bill, and check your monitoring system.

1. If you have an ordinary string inverter (that big box hanging on the wall near your electric meter), all you need to do is make sure the green light is on and that the inverter’s display indicates that power (measured in watts) is being generated. Usually you should see peak output around noon, and on a sunny day this output will usually be about 75% of the rated DC output of your system.

2. Another way to check your system’s operation is to see if your electric meter is running backwards on a sunny day -- but note that the amount of power you are sending back to the utility (usually in kw) is the net of what your solar generates minus what your house is currently using.

3. You should also keep an eye on your monthly electric bill -- a sudden increase in kwh billings from your utility could be a sign that your system is not operating properly (or the weather was hot and your AC was cranking).

4. Systems with monitoring are easier to manage, both for you and your installer. There are two types of monitoring: system level and panel level.

System level monitoring involves installing a gateway between your inverter (or microinverters) and your home internet connection. The gateway sends inverter data up to a webpage where you can check your output (at any time) and energy production (during any interval). Panel level monitoring gives you even more granular data, but this type of monitoring requires a microinverter or optimizer on the back of every panel. Although slightly more expensive, panel-level monitoring makes it easier for you or your installer to make sure your system is operating properly. It is important to note that the most common solar service calls are due to monitoring problems, and these monitoring problems do not necessarily mean that your system is not producing power (usually there is just a problem with your internet connection or gateway).

For more on the benefits of monitoring your rooftop solar system, please Listen Up to this week’s Energy Show on Renewable Energy World.

People with rooftop solar systems almost always ask about using batteries to store their energy for nighttime use. Tesla recently announced an off-grid battery storage system, SolarCity announced a home backup power system, and a dozen other companies already have comparable products on the market. These announcements have re-energized (grin) the hype and excitement in this new product category. But are these systems practical and will they save you money?

For the vast majority of homeowners, the answer is “no” to both questions. Only if you have a completely off-grid application -- such as a cabin in the woods -- can the new generation of lithium ion battery backup systems combined with solar be more practical and cost effective than traditional lead acid batteries. If you are currently on the grid, energy arbitrage makes no sense at all: with current electric rates it is simply not cost effective to generate your own energy with solar during the day and use it at night (or buy cheap electricity at night and sell it back during the day). In a nutshell, the life cycle cost of the batteries outweigh any potential savings. If you are looking for backup power during a blackout, a generator is still the cheapest way to power your house for a few hours or a few days.

Nevertheless, there is no doubt that batteries will continue to improve, and control electronics will get cheaper and more efficient. Besides the current off-grid and backup power applications of home energy storage, there will come a time in the future when home energy arbitrage (buy low and sell high) and grid support services will make economic sense. If you’re curious about the practicality of home battery storage systems, please Listen Up to this week’s Solar Energy Show.

Unlike other home appliances, HVAC systems and vehicles, there is virtually no maintenance required for a well-installed rooftop solar system. So unless you are paranoid, or just cursed by bad luck, there is no need to pay anything extra for a service contract or scheduled maintenance.

Why are rooftop solar systems so reliable? First, because the solar panels themselves have zero moving parts, use tempered glass and anodized aluminum (better than most windows and skylights), and are covered by a 25 year manufacturer’s warranty. Second, because top quality microinverters carry a 25 year warranty and string inverters carry a 10 year warranty — and based on industry experience, the real-world performance of quality inverters has exceeded their warranty term. And third, because flashed rooftop mounting systems using all aluminum and stainless steel components will last at least as long as a homeowner’s roof.

If your last name is Murphy you may ask: “what could go wrong?” If you live in a dusty or dry area, you may want to have your solar panels washed periodically. Monitoring systems are susceptible to occasional internet communications glitches — but these communications glitches have no affect on your system’s energy output. If you have a string inverter, it is reasonable to expect replacements after 10-15 years (at Cinnamon Solar we regularly replace 10+ year old string inverters). Otherwise -- except for your roof wearing out -- you can expect 25+ year of trouble free operation of your system.

But if you are paranoid or cursed by bad luck, carefully check the terms of the maintenance agreements that are offered by your solar installer. And run the numbers yourself to see how much this “all inclusive” maintenance will really cost. The things that do go wrong are almost always excluded from coverage (such as panel cleaning or rodents chewing wires), and the things that are included (such as a defective inverter or solar panel) are almost always covered by the manufacturer’s warranty. So please Listen Up to this week’s Energy Show on Renewable Energy World for a practical overview of home solar maintenance requirements.

Understanding A Home Solar Sales Pitch by Barry Cinnamon

A rooftop solar system is an expensive up-front investment. The typical 5 kw system costs about $20,000 – or $14,000 after the 30% investment tax credit (which expires on 12/31/16). Solar leases and loans have made it possible for hundreds of thousands of homeowners to go solar without any initial up-front investment. Now there is a new solar financing product called PACE that makes it easy for just about any homeowner to qualify for a low interest solar loan.

PACE stands for Property Assessed Clean Energy. A PACE loan is repaid as part of a homeowner’s annual property tax assessments, and is automatically transferred to the new owner as part of the property. For example, a $20,000 rooftop system could be repaid in 15 annual tax bill payments of about $1,500. If the home were sold after ten years, the new owner would simply take over the remaining five years of principal and interest payments. Interest rates and terms on PACE loans are about the same as standard bank loans. Since the loan is secured, interest payments (and sometimes principal) are tax deductible. What’s the hitch? PACE loans are not yet available everywhere. But as they proliferate, PACE loans will become another popular way to finance rooftop solar.

My guest this week is Cisco DeVries, CEO of Renewable Funding. Cisco pioneered the use of PACE financing for rooftop systems in Berkeley in 2007, and is now working to roll out PACE for both residential and commercial installations all over the U.S. Please Listen Up to this week’s Energy Show for more details on how a PACE loan could work on your own home – or your next solar project.