Produce All the Energy You Need, without Sacrificing Comfort or Convenience: How One Silicon Valley Family Did It
Indradeep Ghosh lives in Silicon Valley with his wife and two children. A few years ago, inspired in part by the film, “An Inconvenient Truth,” Ghosh began a quest to end his family’s direct consumption of fossil fuels. His goal was to do this without taking on a “minimalist lifestyle,” but to maintain his family’s current levels of comfort and convenience. Along the way, he learned a number of lessons, including many tips and tricks that can be applied by any homeowner, even those with more modest energy-efficiency goals. Ghosh shared his story with a rapt audience at the 2/7/13 meeting of the EcoGreen Group in Santa Clara.
The Ghosh household was typical of Silicon Valley, with two working adults, two school-age children and two gasoline-powered cars. Their home, built in 1997, comprises 2200 square feet, just about average for its vintage. Between the home and cars, Ghosh estimated that they were directly using the equivalent of 41,600 kilowatt hours (kWh) of energy per year. (He converted gasoline and natural gas consumption into kWh equivalents.) With a goal of “zeroing out” his electric, gas and gasoline bills, Ghosh set out to discover whether it was possible. He learned all he could about energy-efficiency and renewable energy that might be applicable to a typical middle class home. Then, he laid out four clear steps to his destination.
Step 1 – Energy Efficiency
Ghosh needed to get an idea of how his family was using those 41,600 kWh of non-renewable energy. So, he conducted his own whole house energy audit. Using a combination of measurements from a Kill-a-Watt meter and readings from his utility meter, he developed a pie chart that showed how the family used power. (You can borrow a Kill-a-Watt meter from the local library. Here’s a link to the meter on the Santa Clara County Library website. Or if you live in Los Altos or Los Altos Hills, you can get a free online energy assessment. Check it out here. The first 50 Los Altos homeowners who sign up, will get a free assessment, courtesy of GreenTown Los Altos. All homeowners in the Town of Los Altos Hills may obtain a free online energy assessment. See the town’s sustainability page for more info.) For the Ghosh household, the biggest uses of energy were typical of a Silicon Valley home:
- Heating and Cooling
- Water Heating
- Lighting and Appliances
As a result of his audit, Ghosh made the following changes:
- Replaced 50 lightbulbs with LED lights. This reduced his lighting load from 900 watts to 150 watts. While the LED lightbulbs are more expensive than compact fluorescent bulbs (CFLs), Ghosh points out that they may last longer and they do not contain mercury (a hazardous waste contained in CFLs).
- Replaced all appliances with EnergyStar appliances. These typically consume less energy than older, less efficient appliances.
- Reduced standby power use by installing a cut-off remote device. This consists of receivers with electrical plugs that are inserted into certain outlets and then turned off by using a remote control.
- Did not improve the home’s insulation. Since he had a newer home (built in 1997) with double-pane windows and good insulation, R20 in the walls and R50 in the attic, he decided it was not worth the expense to make improvements. (In his case, this would have necessitated drilling holes in the walls and blowing in insulation.)
- Installed a programmable thermostat so that he could better manage his use of heating and cooling. He aims for 68-70° in winter and 79-81° in summer.
- Replaced the water heater. Ghosh knew that he wanted to electrify his home (and not use any natural gas), so he replaced his water heater with a heat pump water heater (more on that later). If you plan to operate a natural gas-powered water heater, he recommends that you ensure that it is well-insulated. (Newer models include internal insulation.)
- Changed water fixtures and habits. In order to reduce the amount of water heating required, Ghosh replaced his faucets and showerheads with low-flow fixtures. (This has the additional benefit of conserving water.) The family makes sure to wash only full loads in the washing machine and uses only cold water for washing.
Step 2 – Home Electrification
Since Ghosh was planning to power his home solely through rooftop solar panels, he needed to eliminate his home’s use of natural gas. Here’s what he did:
- Replaced gas cooktop with an induction stove top. This was a big win in terms of energy efficiency since a gas cooktop is only 40% efficient (i.e. only 40% of the gas burned is used for heating food; the rest is wasted) and an induction cooktop is 85% efficient.
- Replaced the natural gas-powered water heater with a heat pump water heater. A heat pump water heater uses electricity to move heat from one place to another instead of generating heat directly. (See this description on the website of the U.S. Department of Energy.) According to Ghosh, this type of water heater is 100-300% energy-efficient compared to a natural gas water heater which is typically 58% efficient (i.e. uses only 58% of the natural gas to actually heat water and wastes the rest). The reason the heat pump water heater can exceed 100% efficiency is that, most of the time, it is just capturing and moving (i.e. pumping) heat from the surrounding air into the water rather than using electricity to directly heat the water. However, when the air temperature surrounding the water heater is so cool that this heat transfer is no longer efficient, then the water heater does use electricity to heat the water. The efficiency claim is debatable and depends on the conditions in which it is installed. (See this post from BuildingGreen.com.)
Replaced the gas furnace with an air source heat pump. Ghosh estimated that his gas furnace was about 80% energy efficient (i.e. uses 80% of the energy for heating the air and wastes the remaining 20%). An air source heat pump which uses electricity to move heat from one place to another would be more efficient. This was one of the most expensive retrofits due to the installation costs, which brought the total to about $8,000 ($3,000 for the system and $5,000 for installation).
Step 3 – Electrify the Cars
The Ghosh family’s gasoline-powered cars comprised the majority of the family’s fossil fuel consumption. The family decided to keep one of their existing vehicles, a Toyota Highlander Hybrid vehicle that averages 28 MPG. This vehicle is now used only for camping trips or when large items must be transported. Ghosh purchased two new vehicles which are used for most trips, including commuting. Ghosh considered purchasing two new all-electric vehicles but compromised with his wife since she had some range anxiety (i.e. the concern that the vehicle’s electric charge will not be sufficient to go a desired distance). The Ghoshes purchased:
- Chevy Volt electric/gas hybrid car – This vehicle has a range of 40 miles on electricity and then relies on gasoline for distances beyond that. It gets the equivalent of 500 miles per gallon given the family’s driving habits. Ghosh estimates that this car requires about 3000 kWh per year to power its annual usage of 10,000 miles.
- Ford Focus all-electric car – This vehicle has a range of 80 miles. The family drives this car about 5,000 miles per year and it requires 1600 kWh per year.
Step 4 – Renewable Energy – Solar Power
After Ghosh improved the energy efficiency of his home (Step 2 above), he estimated that he would need about 9,900 kWh per year to power his home and an additional 4,600 to power the two electric cars for a total power requirement of 14,500 kWh per year. A 10 kilowatt solar system would meet his needs if all his solar panels were optimally positioned and facing south. However, he had to account for several factors in sizing his system:
- Not all the solar panels could be optimally positioned for maximum power generation, given the angles and slope of his roof.
- Losses occur when converting the direct current (DC power) to alternating current (AC power used in U.S. homes).
- There is an expected degradation in the power production of the panels over time – about 0.5% per year – and Ghosh wanted the system to produce plenty of power over the long term.
Ghosh has a PhD in electrical engineering and seemed to enjoy the process of designing his own system, which he says took the equivalent of three full weeks of his time. He purchased his solar panels and related equipment (e.g., inverters) online for about $3/watt (before rebates) – a significant costs savings on materials. He then had to search for a company to install the panels. The only local firm that was willing to do so was Intelisolar.
The Bottom Line for the Ghosh Family
The Ghosh family ended up reducing their total direct fossil fuel consumption (house and cars) by an estimated 65% and have eliminated their electricity, natural gas and gasoline bills (except for a very small amount of gasoline purchased for the occasional use of their Toyota Highlander hybrid vehicle).
Energy Consumption (kWh or kWh-equivalent)
|House Alone||House + Cars|
Ghosh estimated that he spent a net amount of $49,000 and expects that this will investment will be paid back in 11 years. (See table below.) Ghosh expects that the amount required for these investments will continue to decline as the benefits increase with the rising cost of power. For his family, the best investment was in the vehicles, especially given the extraordinary level of rebates and incentives.
Investments, Rebates ($000’s)
|Home Retrofit||Cars*||Solar Power||Total|
* The cost of the cars is the estimated premium paid
over the cost of similar, gasoline-powered cars.
Ghosh also recommends that homeowners calculate a statistic of kWh/square foot for their home to assess its energy efficiency. He likened this to an MPG for your home. The Ghosh home uses 4.5 kWh/square foot/year (9,900 kWh/year ÷ 2200 square feet), which compares to ratings for typical Energy Star homes on a rating scale that Ghosh compiled from various sources.
How Does Your Home Compare?
If your home uses both natural gas and electricity (true for most of us in Silicon Valley), you must first convert your natural gas usage to kWh equivalents by multiplying the therms used times a factor of 29.3 to obtain kWh. Here’s how to calculate your home’s efficiency rating:
- From your electric bills, total the total therms of natural gas used for a 12-month period. Multiply total therms by 29.3 to obtain kWh equivalent.
- From your electric bills, total the total kWh of electricity used during the same 12-month period. If all your electricity is sourced from the grid (i.e. not generated at your home via solar panels), then, according to Ghosh, you should multiply the kWh from your electric bills by 2 because only 50% of the primary energy used in generating stations in California is actually delivered to the consumer.
- Add the two amounts calculated above for your total kWh equivalent used during a year.
- Divide the calculated annual kWh usage by the total “conditioned” square footage of your home (typically does not include unheated garage space). This is your home’s efficiency rating.
- Compare to the scale below to see how your home stacks up!
Energy Efficiency Rating (kWh/square foot/year)
Minimalist: 0 – 2.5
Passive House: 2.5 – 4
Energy Star: 4 – 7
Energy Conscious: 7 – 10
Most U.S. Homes: 10-20
Wasteful: over 20