BAYREN Guide to Fossil Free Homes

This guide can help you replace natural gas heating, water heating and appliances to go low-­‐‑ or zero-­‐‑ carbon in your home, and you don’t necessarily need solar panels to do it.

Solar and Electric Vehicles (PV + EV)

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Solar and Electric Vehicles (PV + EV)

With a rooftop solar system generating clean energy, and an EV using clean energy, you can enjoy a superb alternative to dirty expensive electricity and dirty expensive transportation at the same time.

Natural gas still provides about half of all electricity generated in California. While natural gas is promoted (most loudly by the natural gas producers) as much cleaner than coal, several recent studies have shown that leakage through the exploration and production process from drilling to storage to transportation to refining and combustion in power plants, may release as much greenhouse gas per unit of energy as coal. Although less toxic than coal, natural gas can pollute the water (such as the infamous “Light Your Water on Fire” YouTube video) and air (such as with the 2105 Aliso Canyon gas leak in California) .

Once rooftop solar panels are installed, you’ll start generating 100% clean energy. This will continue for at least the 25-year warranted life of the solar panels. When you charge your EV at your solar-powered home, you won’t be sending energy directly from your panels to your car (especially when you charge at night!), but you’ll be driving with “net zero carbon” by providing as much energy to the grid as you take from the grid.

When your EV is charged with solar energy, you can drive your clean, quiet, responsive, low maintenance, conversation-starting EV in the carpool lanes and express lanes even as a solo driver. The Bay Area is fortunate to have many public charging stations, with more on the way, and there are now several models of EV with a range of over 100 miles:

  • Audi eTron – 204 miles
  • BMW i3 – 153 miles
  • Chevrolet Bolt – 238 miles
  • Ford Mustang Mach-E – 230 miles
  • Hyundai Ioniq – 124 miles
  • Hyundai Kona EV – 258 miles
  • Jaguar I-Pace – 234 miles
  • Kia Niro EV – 239 miles
  • Nissan LEAF – 150 miles
  • Nissan LEAF PLUS – 226 miles
  • Tesla Model 3 Long Range – 310 miles
  • Tesla Model 3/ Standard Range – 240 miles
  • Tesla Model S Long Range – 370 miles
  • Tesla Model S Standard Range – 285 miles
  • Tesla Model X Long Range – 325 miles
  • Tesla Model X Standard Range – 255 miles
  • VW e-Golf – 125 miles

What does it cost to drive these EVs on sunshine?

To get started, there’s one number that’s handy to know: 3.5 to 4 miles per kilowatt-hour (kWh). Just about every electric car will go 3.5 to 4 miles per kWh. Unlike gasoline cars (known to EV drivers as ICE cars, for Internal Combustion Engine), which range from under 10 miles per gallon to over 50, EVs have very similar efficiency ratings. A 100 horsepower Leaf and a 500 horsepower Tesla both travel 3.5 to 4 miles per kWh. The Nissan Leaf with a 30-kWh battery will go about 107 miles. That’s 3.6 miles per kWh.

How much does your electricity from the grid cost? You can determine this from your PG&E bill. The Bay area EV off-peak average is about 12¢ per kWh, and 12¢ worth of grid power would drive your Leaf 3.6 miles. That’s 3.3¢ per mile.

How much does an ICE car cost in fuel? Say you have a 30 MPG car. California just raised the price of gas by 12¢ per gallon and the average in the bay area is now a little over $3/gallon. 30 MPG at $3/gallon means your fuel cost is 10¢ per mile. Great, your EV is already 67% cheaper using grid power!

How much does electricity from your solar panels cost? This involves dividing the total cost of your solar system by the total number of kilowatt-hours (kWh) it will produce over its warranted 25-year lifetime. It will depend on the price of your solar, and the math is a little complex for this article. However, a typical SunWork system, such as our 500th installation was $7,286 for 3.48 kilowatts. Add $1,000 for an inverter that will need replacement over 25 years because in this case, the inverter has a 10 year warranty. The 3.48 kW system will produce about 115,000 kWh over 25 years. Divide $8,286 by 115,000 kWh means the 25-year cost of electricity will be 7.2¢ per kWh. This is one third the cost of grid electricity now, and it’s set for 25 years, while PG&E rates are likely to climb.

Cost per mile

10¢ Internal Combustion Engine car
3.3¢ EV with grid power
2¢ EV with SunWork solar system

At 7.2¢ per kWh for solar and an EV’s 3.6 miles per kWh, that’s 2¢ per mile, which is 20% of the cost of the ICE car. And that’s just the “fuel.” In an EV there’s no need to change the oil, there are no valves or pistons or intake manifolds or catalytic converters or fuel injection systems, or smog checks. There’s barely a transmission in an EV since most have just one gear.

Rooftop solar plus with an electric vehicle gives you much cleaner, much cheaper energy and transportation. PV + EV is our future, and there’s nothing mysterious or unproven about it. Consider joining the hundreds of thousand Californians who’ve already gotten started.

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Electrification of Home Heating/Cooling

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Electrification of Home Heating/Cooling

-Sonja, SunWork Volunteer

Heating and cooling your house is one of those things you don’t think much about until the temperature starts to dip in the winter months or peak in the summer months. Our house, a 1400 sqft single story in Sunnyvale, had a natural gas central heating system but no air conditioning. For the hottest summer days it was not uncommon for the temperature to reach the mid 80s inside. Even though there is some insulation on the roof, the very low slope means it has no accessible attic space to easily add more. Another complaint my family had was the furnace, located in a closet central to the house, right next to the dining room and bedroom. Being an older model it was loud; so loud you needed to vacate the dining room if you wanted to converse without shouting across the table. It was time for a better solution.

Since our goal was to improve both the heating and cooling inside our house, a heat pump space heater was the ideal solution. An Air Source Heat Pump (ASHP) is much like an air conditioner except that, in addition to providing cooling, it can be reversed in the winter months to provide heating. It is a two-unit system. There is an outdoor unit that either heats or cools a refrigerant fluid. That refrigerant is piped to the indoor air handler unit which in turn blows conditioned air throughout the home’s duct system.The heat pump we chose is a variable speed Mitsubishi PUZ-A30NHA7(-BS) and the air handler is an ultra quiet Mitsubishi PVA-A30AA7 with a supplemental Electric Heat Kit EH05-MPA-MB. Our HVAC installer removed the old natural gas furnace and repurposed that closet for the air handler and supplemental heat kit. All three units run on electricity so our installer capped the natural gas line that was previously used by the furnace. Our final cost for equipment and installation came in just under $12,000.

Health Benefits

Our utility company provides 100% carbon free electricity, so we now heat and cool our house in an environmentally-friendly way. Plus, by eliminating the combustion of natural gas we are improving our indoor air quality and our health.

Single Zone or Multi-Zone

In our situation, because we already had ducting throughout the house, it made sense to reuse the existing ducting to distribute the conditioned air. This is known as a Single Zone system. However, a centralized duct system is not the only option; you can also eliminate the ducting and use a mini split to condition a single room or a section of the home (aka Multi-Zone system).

Living with a Heat Pump

As of this writing my family has been through a full heating and cooling year. The ultra quiet air handler has been a dream come true in terms of its whisper quiet operation. Our outdoor heat pump unit, being able to operate at variable speeds, has also been pleasantly quiet – a great benefit since it is located immediately outside a bedroom window. The heat pump has performed perfectly in keeping our house comfortable year round – especially compared to our previous summers when we did not have air conditioning. One adjustment we needed to make is our expectation for how quickly the heat pump is able to heat the house. Compared to our old furnace, the heat pump takes more time to get the house up to temperature. As a result we have adjusted our thermostat to keep the house in a more narrow temperature band and to start heating the house sooner in the mornings – an easy enough fix with a programmable thermostat. Switching away from natural gas and towards electricity for our home heating/cooling of course means we are spending less on natural gas and more on electricity. As our lifestyle becomes more and more electrified, it has turned our attention to our next home improvement project, adding a solar PV system!

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Battery Backup

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Battery Backup

In general, an existing solar system can be upgraded to add battery backup. However, it is expensive and SunWork does not install batteries at this time.

Installing batteries for backup purposes can cost $15,000 to $30,000 depending on your situation and on how much backup power you want to maintain.

There are state and federal incentives that can help; however, the state incentive can be tricky and the federal tax credit has limitations as well. Here is a link to information on the California state incentive for batteries and here is a link to an article on federal tax credit.

We have a chart of some of the backup options. You can find it here.

There are two types of grid connected battery options when connecting to a solar system. One is called AC-coupled and the other is DC-coupled. The AC connected system is easier and less costly to add to an existing solar system. The DC connected battery requires replacing your current solar inverter with an inverter that manages both the solar and the batteries, however it is a bit more efficient. In my opinion, it’s not worth replacing your existing solar inverter, however, there may be other advantages depending on your situation. Here is an article that discussed these two options and here is a good video.

Here is an article that provides some information on inverter selection. For example, for the SMA SunnyBoy, you would typically install the SMA Sunny Boy Storage (the updated version of Sunny Boy Island) although some batteries include their own inverter such as the Tesla Powerwall and Sonnen. Here is an article comparing different battery options. The article is from Australia which has a lot of experience in this area and most of the information on the major batteries such as Tesla, LG and Sonnen are valid in the US as well.

Be prepared to have your main service panel redone so that it can isolate the loads in your house and the solar system from the rest of the grid during a power outage. This is called a critical load center. The system also needs to ensure that no power can leak onto the grid while the power lines might be getting worked on. Once the system cuts ties with the grid, it can incorporate any connected solar system and trick it into thinking the grid is present by basically creating its own micro-grid using its battery pack.

A low-cost solution is a portable generator either powered by gas or one that has a battery and can be charged by a regular outlet or by a solar panel. Batteries that can be charged by solar are often called “portable solar generators.” See this Best Home Backup Solar Generators 2020 article which provides a good overview of 6 solar generators currently available. A recent new option called the EcoFlow Delta 1300 is reviewed here.

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Volunteer Training Announcement

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