The Value of Solar and Vermont’s Renewable Energy Goals
Acadia Center released its latest “Value of Solar” study this month, this time quantifying the grid and societal benefits of solar photovoltaic systems (solar PV) in the state of Vermont. The study highlights the unique value solar PV provides to the electric grid by reducing energy demand, providing power during peak periods, and avoiding generation and related emissions charges from conventional power plants.
Through evaluating six solar PV systems, Acadia Center determined that the value of solar to the grid – and ratepayers connected to the grid – ranges from 19-23 cents/kWh in the Green Mountain State, with additional societal values of 7 cents/kWh. The societal values are based on broader societal benefits, including environmental gains from reduced or avoided greenhouse gas emissions and other pollutants.
Vermont has been working to capitalize on the value of solar and other renewables already. In June, Vermont House Bill 40 was signed into law, creating a new requirement that 55 percent of the power sold by Vermont energy companies must come from renewable sources by 2017. That figure rises to 75 percent by 2032.
This target is the highest anywhere in the US except for Hawaii, which just enacted a law mandating the state use 100% renewable energy by 2045. However, because Vermont’s target can be met using energy from existing renewable energy plants, including hydro power, the overall requirement on its own is not projected to lead to new renewable energy facilities being built.
As a part of the total requirement, utilities are also required to use distributed generation equivalent to 1% of retail electric sales in 2017, and increasing annually to 10% by 2032. This is expected to lead to the build-out of over 400 MW of small-scale, decentralized electricity generation in Vermont, including solar PV.
This is not the first time Vermont has been ahead of other states in clean energy. At the beginning of the year Burlington, the state’s biggest city, announced it was using 100% renewable energy to meet its residents’ electricity needs, making it the first city in the country to do so.
As the state as a whole looks to reach the goals set by the new renewable energy standard, Acadia Center’s study will underline the value that solar provides to the grid and ratepayers.
Ellen Hawes is a senior analyst at Acadia Center focusing on energy systems, land use and carbon markets. She also leads Acadia Center’s participation in the New Hampshire State Energy Strategy process. Ellen received her Master in Forestry from the Yale School of Forestry and Environmental Studies.
RGGI Provides Both Economic and Environmental Benefits
A new report from Acadia Center highlights the benefits of the Regional Greenhouse Gas Initiative (RGGI), a cap-and-trade program in the New England states, New York, Maryland, and Delaware that started six and a half years ago. The benefits, which stem from emissions reductions and investing revenue the program generates, include declining energy bills, reduced illnesses, and job creation among others.
A cap-and-trade program sets a limit on the amount of CO2 that a region’s electric power generators can release into the atmosphere, with that cap level dropping each year. Companies can purchase permits to release CO2 (called “allowances” in RGGI) through quarterly auctions, and if companies find that they have too many or too few allowances to cover their own CO2 emissions, they can trade with other companies in order to meet their compliance obligations.
RGGI invests 59% of the auction revenue this process creates in energy efficiency programs that reduce consumers’ bills and reduce demand for power. Lower power demand means fewer emissions from power plants, and less money leaving the region to pay for imported fossil fuels.
Independent macroeconomic analysis found that programs supported with revenue raised over RGGI’s first six years of operation would generate over $1.73 billion in energy bill savings. These savings create over $2.76 billion in net economic gains and over 28,500 job-years of employment.
In addition, contrary to projections, electricity prices have declined since RGGI took effect. Comparing average retail electricity prices from 2008 (the year before RGGI’s launch) to 2014 shows that prices have dropped by 2% on average across the region. During the same 2008-2014 period electricity prices in non-RGGI states increased by 13%.
RGGI State Electricity Prices, 2008 and 2014 (Cents/kWh)
Most importantly RGGI is achieving its main goal, reducing pollution. CO2 emissions from the 167 power plants covered by RGGI totaled 86,307,909 short tons of CO2 in 2014, which was 5.2% below the 2014 emissions cap of 91,000,000 tons. In addition, when plants are required to pay for CO2 emissions it makes it less economical to operate dirtier plants in comparison to cleaner generating sources. This along with regulations outside RGGI specific to hazardous pollutants helps reduce sulfur dioxide (SO2), nitrogen oxide (NOx), and mercury (Hg) emissions.
Reducing emissions of hazardous pollutants leads to health savings by avoiding illness, hospital visits, lost work days, and premature deaths. In monetary terms, the reduction in hazardous emissions from RGGI’s launch (January 1, 2009) through 2014 translates into nearly $11 billion for SO2 and NOx combined.
Reduction of Hazardous Pollution
These benefits show that RGGI offers a proven, cost-effective pathway to achieve emissions reduction targets. Which is why, with a few adjustments, Acadia Center believes RGGI is a model program for states to adopt in order to meet the Environmental Protection Agency’s (EPA) forthcoming Clean Power Plan (CPP) requirements. When EPA’s final carbon pollution standards are released (which could be as early as next week) we will provide an update on implications for RGGI.
Peter Shattuck is the Director of Acadia Center’s Clean Energy Initiative and our Boston office. Peter’s work at Acadia Center focuses on cleaning up the energy supply across all sectors of the economy. Driving market-based emissions reductions is at the core of this work, using cap and trade policies such as the Regional Greenhouse Gas Initiative, which Acadia Center has tracked since the program’s early development in the 2000s and which Acadia Center is now promoting beyond the region.
Jordan Stutt is a Policy Analyst in Acadia Center’s Boston office. He works on energy, transportation and climate change issues, with an emphasis on research and policy analysis for energy systems and carbon markets. He was an Energy Policy Analyst at Pace Energy and Climate Center, Pace University Law School in White Plains, NY, where he focused on energy efficiency and RGGI.
Weatherization: Where We Are Now and Where We Could Be
It has become conventional wisdom that our region’s existing building stock needs to be weatherized in order to meet our climate goals and put us on a path to a sustainable future. The energy consumed in the region’s homes, largely from imported fossil fuels, accounts for 21% of all greenhouse gas emissions. Reducing those emissions is a key component of any climate change mitigation strategy. But what does weatherization really mean, and how can we get there? Weatherization generally refers to improvements in a home’s shell, or envelope, that separates the indoors from the outdoors. The main tools for weatherizing a home are sealing gaps to prevent unwanted air leakage and improving the insulating value of ceilings, walls, and windows.
While it sounds easy, for many homes weatherization can be a real challenge. There is often work that needs to be done first before the weatherization upgrades can be performed – asbestos that needs to be removed, outdated wiring that can’t be insulated over, and much more. In addition, there are complex weatherization projects that are just much more expensive than simple ones – insulating brick buildings or air sealing older walls with lots of hidden seams. Buildings that have some insulation, but not the optimal amount, will cost nearly the same amount to upgrade as a building with no insulation, but the savings will be less. The result is that at today’s energy prices, many weatherization projects will take a very long time to pay off and are just not attractive to homeowners.
Fortunately, weatherization makes sense for the majority of homes in the region, and we’re making significant progress in this area. The energy efficiency programs in the New England states are helping hundreds of thousands of residents make weatherization improvements every year. These programs make it easy for consumers to get their homes assessed, get started on upgrades, and get unbiased information on the next steps toward additional improvements. The programs are delivering real savings – to the participants and to our energy system, as well as emissions reductions.
For those weatherization projects that don’t make financial sense for a consumer based on energy savings, do we still want to encourage them? The answer is generally yes – assigning a realistic price to greenhouse gas emissions can dramatically change the cost equation. The states in the region need to move toward better valuing the carbon emissions reductions that will be needed to meet mandatory greenhouse gas targets, and then bundling that value into incentives that can be offered to building owners for weatherization through existing energy efficiency programs. To learn more about this important topic, see Acadia Center’s recent publication, “Weatherization and Energy Efficiency as a Resource.”
Jamie Howland leads Acadia’s 
Climate & Energy Analysis Center (CLEAN), and Energy Efficiency and Demand Side Initiative. His work as a policy analyst focuses on data management on energy markets and emissions trends, buildings and land use issues.
Energy Efficiency Winning Out in Rhode Island
The Rhode Island General Assembly has demonstrated its long-standing commitment to reducing the state’s energy costs through smart and economic investments in low-cost energy efficiency. This spring, the legislature approved a 5- year extension of Least Cost Procurement (LCP), the state’s policy of investing in as much low-cost energy efficiency as possible, and created the Rhode Island Infrastructure Bank, a new clean energy financing tool.
Least Cost Procurement, first implemented 8 years ago, is largely responsible for Rhode Island’s tie with Massachusetts for #1 state in the country for utility-sector energy efficiency programs and policies in the American Council for an Energy Efficiency Economy (ACEEE)’s 2014 State Scorecard. Investing in low-cost energy efficiency instead of expensive electricity and natural gas helps Rhode Islanders lower their energy bills and spurs economic growth. Lower utility bills means that Rhode Islanders have more money left at the end of the month to spend on other things, and most of that spending happens locally. Since 2008, Rhode Island has invested $558 million in energy efficiency and consumers have realized $1.99 billion in economic benefits.
The state’s investments in energy efficiency from last year alone are expected to generate 3,607 job years of employment, increase personal income by $244 million, and increase state tax revenue by $15 million over the next thirteen years.
The Rhode Island Infrastructure Bank (RIIB) will work to increase those benefits by utilizing loan-based financing to enhance the state’s energy efficiency programs and make energy efficiency projects more accessible for RI municipalities, residents, and businesses. The Efficient Buildings Fund at RIIB will provide energy efficiency financing to municipalities for upgrades to public buildings and facilities. RIIB will also administer Property Assessed Clean Energy (PACE) financing for residential and commercial property-owners. PACE allows property owners to borrow money for clean energy upgrades and repay the loan on their property tax bill.
As the RIIB was developed, Acadia Center provided input to policymakers and key stakeholders and shared lessons learned from other states’ experience with clean energy financing. Going forward we will work with stakeholders as they implement RIIB and provide that same support. Acadia Center will continue to represent environmental interests on the Energy Efficiency and Resource Management Council to ensure that Rhode Island consumers benefit from the low cost, low risk energy efficiency resource.
Download Rhode Island’s Legislative Wrap-Up here.
Abigail Anthony leads Acadia Center’s Grid Modernization and Utility Reform initiative, focusing on changing regulatory and economic incentives in order to achieve a sustainable and consumer-friendly energy system. A Rhode Island native, Abigail is director of the Providence office and has played a leading role in advancing the state’s energy efficiency procurement policies.
What is the Value of Solar Power in Rhode Island? A New Study
A new study released this week by Acadia Center quantifies the grid and societal benefits of solar photovoltaic systems (solar PV) in Rhode Island. Establishing the value of distributed resources like rooftop solar is increasingly important as states explore ways to meet energy needs and deploy clean energy resources.
Acadia Center assessed the grid and societal value of six solar PV systems to better understand the overall value that solar PV provides in Rhode Island. The analysis determined that the value of solar to the grid – and ratepayers connected to the grid – ranges from 19-25 cents/kWh. These values derive from solar PV’s ability to reduce energy demand and provide power during peak periods, thus avoiding generation and related emissions from conventional power plants. The overall grid value of solar is the sum total of these different benefits.
The study also finds that solar PV provides broader societal advantages (such as environmental benefits from avoided greenhouse gas emissions) valued at approximately 7 cents/kWh. This additional value should be considered when assessing costs and benefits and determining additional incentives for solar producers.
One of the key findings is that west-facing solar PV systems in particular are not being adequately compensated under existing programs – like net-metering- which provide a single level of compensation and encourage south-facing installations that maximize kWh output. These programs do not fully account for the value that west-facing systems provide in mitigating costs driven by afternoon peak demand (see Table 1 in the report). Incentives should be designed to maximize the value that solar PV provides to system owners and ratepayer rather than simply encouraging system owners to maximize kWh output. This will help ensure that incentives are fair and optimize grid support.
In fact, the value of west-facing systems is already coming into play in Rhode Island where the Office of Energy Resources has procured 250 kW of peak load reduction – with additional incentives for west-facing solar systems – in the Tiverton and Little Compton area. This is being done in conjunction with National Grid’s “DemandLink” pilot, which is using targeted efficiency and demand response to avoid a new substation feeder in the area; ultimately deferring approximately $2.9 million in new distribution-related costs.
While not included in Acadia Center’s analysis, locational values are important to maximize the savings in distribution costs that solar can bring to ratepayers. Appropriate incentives can ensure that solar PV, energy efficiency, and other customer-side resources are targeted to defer or avoid the need for new infrastructure spending.
This study comes at a particularly interesting time as new solar programs and businesses are being introduced in the state. The Renewable Energy Growth Program, launched this June, gives Rhode Islanders the chance to offset their electricity bills and sell their excess electricity from distributed resources to National Grid through a long-term tariff at a guaranteed fixed price. Programs like these are expected to facilitate a bigger shift toward solar and other distributed generation in the state. As a first step in response to this new trend, the RI Public Utility Commission has opened a docket to assess distribution rate design and cost allocation. Having a better understanding of the value that solar provides to the grid and ratepayers will help inform this proceeding, which could be precedent setting for other jurisdictions.
Leslie Malone is a Senior Analyst at Acadia Center based in the Providence office. Leslie is involved in research and analysis of energy efficiency and clean energy, specifically solar.
Envisioning the Energy Future for Rhode Island: Event Recap
On June 26, Acadia Center hosted UtilityVision: A Discussion about the Clean Energy Future for Rhode Island at The Rhode Island Foundation in Providence. The objective was to provide an in-depth look at what the clean energy future could be for Rhode Island and beyond, as well as engage diverse stakeholders to work through the various challenges to implementation. Acadia Center’s presentation described a practical and positive pathway to achieving Rhode Island’s climate change goals and recommendations for reforming the way the energy system is paid for and planned.
The meeting brought together a diverse group of Rhode Islanders who are thinking about the future of the state’s energy system. Attendees included representatives from clean energy companies, universities, state and federal policy makers, consumer and environmental advocates, state environmental agencies, and the media.
Following the presentations, attendees enthusiastically participated in discussion groups led by Acadia Center staff. The discussion groups each focused on: investments in big infrastructure like pipelines and their impact on Rhode Island’s clean energy future; the changes necessary to fully benefit from new clean energy technology; the reforms needed to align utility incentives with consumer and environmental goals; and the challenges energy efficiency programs face.
These topics sparked lively dialogue and some insights including:
- Rhode Island has nation-leading energy efficiency programs, but there are still hard-to-reach sectors like renters that struggle to benefit from them. If municipalities require landlords to share past energy bills with prospective tenants or create a minimum energy standard for all rental housing, it could ensure that all renters are protected from burdensome energy bills.
- Rhode Islanders need to make sure the right questions are being asked about proposals to publicly finance expanded natural gas pipelines that could lock the state into an outdated energy system for the next half-century. Decision-makers should ask more questions about potential lower risk, lower cost, and cleaner solutions.
- New electric technologies, like electric vehicles (EVs) and battery storage, have the potential to help Rhode Island meet its climate change goals. However, there are barriers to consumer adoption of EVs in the region, including reluctance by auto dealers to market them due to the need for more time spent educating the consumer and lower future revenue potential from vehicle maintenance. Utilities may need different financial incentives in order to be full partners in promoting electric vehicles and help overcome these barriers.
In the coming months Acadia Center will address many of these concerns by participating in the development of the state’s 2016 Energy Efficiency and System Reliability Program Plan, and in the RI Public Utilities Commission’s proceeding on reforming electric distribution rates in light of a changing energy system. We hope to stay connected with those who joined the event to provide updates and coordinated support for progress toward a clean energy future.
Abigail Anthony leads Acadia Center’s Grid Modernization and Utility Reform initiative, focusing on changing regulatory and economic incentives in order to achieve a sustainable and consumer-friendly energy system. A Rhode Island native, Abigail is director of the Providence office and has played a leading role in advancing the state’s energy efficiency procurement policies.
Protect Consumers and Savings –Don’t Raise Fixed Charges
At legislatures and regulatory bodies across the country a debate rages on over consumers’ control of their electricity bills. The debate centers on fixed charges, a monthly fee to obtain access to electricity that applies regardless of how much electricity a consumer actually uses.
Utilities are in favor of increasing fixed charges because it would increase certainty: the utility knows that it will collect a certain amount of revenue from all of its customers each month, regardless of the amount of electricity consumed. Consumers and their advocacy allies, on the other hand, are pushing to prevent these increases because they would reduce consumer control over energy bills, undermine the clean energy future, and reduce economic incentives for consumers to invest in energy efficiency and distributed generation.
Acadia Center recently analyzed the impact of increasing fixed charges in Rhode Island in a revenue-neutral scenario. In this scenario the utility is not allowed to increase the total amount of revenue it collects, just redistribute the total between fixed charges and the variable charges based on consumer’s energy use. National Grid will be proposing revenue-neutral changes to the fixed and variable charges in July, as required by Rhode Island Renewable Energy Growth program law. The analysis determined that if the fixed portion of the bill is increased, then the per-kilowatt-hour charge will be lowered because less revenue will need to be collected in that way (see table below). This essentially means that any effort consumers make to lower their energy usage and become more efficient will be less valuable because the majority of their bill is fixed.
Percent Change in Variable Rates Compared to the Current $5 Fixed Customer Charge and Revenue Requirement for Residential Customers in Rhode Island
| $10 Fixed Charge | -22% | $10 Minimum Bill | -6% |
| $15 Fixed Charge | -44% | $15 Minimum Bill | -17% |
| $20 Fixed Charge | -67% | $20 Minimum Bill | -36% |
| $25 Fixed Charge | -89% | $25 Minimum Bill |
-60% |
The analysis also showed that a significant number of Rhode Island customers—those using less electricity than the monthly average — would see an increase in their electricity bill if fixed charges were increased above the current $5/month; higher usage customers’ bills would go down due to the lower variable rate. These results show that high fixed charges are regressive: low-use customers see their bills increase, while higher-use customers see their bills decrease.
Impact of Higher Fixed Charges by Monthly Usage Level Compared to the Current $5 Customer Charge and Revenue Requirement for Residential Customers in Rhode Island
Acadia Center recommends that policymakers and regulators avoid reliance on fixed charges. Instead, policymakers should consider the following recommendations for short-term reforms that protect consumers and maintain incentives to use energy wisely:
- Adopt a narrow definition of fixed charges. Limit fixed charges to the cost of keeping a customer connected to the grid, such as metering, billing, and the service drop. The impact of public policy considerations should be factored in as well.
- Increase transparency. The components of a cost of service study that are included in the fixed customer charge, and the data, process, and methodology used to determine the components, should be publicly available and easily accessible.
Envisioning the Energy Future for RI: Making the System Work for Consumers and the Environment
As consumers become more aware of the costs and impacts of energy use on health and the environment, we’re looking for ways to re-envision the energy system. With emerging technologies and approaches, a new system is possible.
Acadia Center invites you to a discussion, hosted by the Rhode Island Foundation, which will lay out a strategic plan to achieve a new system that meets our energy needs and supports a fair, healthy economy and environment.
Acadia Center staff will tell the story of how we can get there. The presentation will draw on the user-friendly visuals, recommendations and original research in our recent reports EnergyVision and UtilityVision, with background on trends from ClimateVision 2020. It will show an optimistic and achievable pathway for making deep greenhouse gas reductions and introduce specific recommendations for advancing a consumer- and environmentally-friendly clean energy future. The presentation portion will be engaging and brief, leaving plenty of time for questions and discussion. We hope you will join us.
When
Friday, June 26 10 AM – 12 PM
Where
Rhode Island Foundation
1 Union Station
Providence, RI 02903
We encourage you to use public transportation, but the Rhode Island Foundation is generously offering to validate parking.
RSVP
If you plan to come, please register on our Eventbrite page. The event is free and all are welcome to register.
Support a Clean Energy Future: Event Recap
Acadia Center is grateful to our friends and colleagues who made it out to Boston’s District Hall on a rainy Monday night to share in conversation about realistic pathways to a brighter, clean energy future.
Acadia Center provided updates on efforts to re-energize state leadership to address climate change, reduce emissions and advance clean energy. Staff experts were on-hand to answer questions and engage in discussion on key issues such as extending MA’s leadership on energy efficiency; increasing incentives and infrastructure for electric vehicles; harnessing solar power and other clean energy resources; and, leveraging RGGI and carbon markets.
Leslie Malone, Senior Analyst, shares results of Acadia Center’s Value of Solar study for Massachusetts
Posters with infographics and charts helped jumpstart conversation and showcased a key element of Acadia Center’s approach: credible research with user-friendly visual presentation that tells a story. Some recent publications include EnergyVision and UtilityVision, which illustrate pathways to deep carbon reductions and a consumer-friendly energy system.
Acadia Center President Daniel Sosland displays UtilityVision, a framework for advancing a modern clean energy grid that literally paints a picture of what our clean energy future could look like
Please join Acadia Center for our next event: Envisioning the Energy Future for RI: Making the System Work for Consumers and the Environment. Friday, June 26, 10am -12pm, in Providence, RI at the offices of the Rhode Island Foundation. Learn more and register here.
Relationship Counseling with Your Utility is Better than Breaking Up
Frustration with utilities combined with declining costs of solar and energy storage has raised the possibility that customers will start divorcing from the grid. Cutting the cord and going “off-grid” has technically been possible for decades, but as costs fall, the idea is starting to gain some real traction. SolarCity, a solar power provider, plans to lease solar photovoltaic (PV) plus storage systems in Hawaii, where high power prices, abundant sunshine and frustration with the local utility has made grid divorce alluring.
While the thought of ending your relationship with a utility may be satisfying, it would undermine our capacity to reduce emissions and set back efforts to modernize the grid.
Battery storage clearly has an emerging and important role in our energy future, but using it to fully sever ties with utilities leaves many of the benefits of both storage and clean generation unrealized. Sure you may feel that you’re trapped in a one-sided relationship, that your concerns and needs are not being addressed, or that the utility does not reflect your values. But rather than cutting the cord, the solution is making structural changes to the grid that will move us toward a clean energy economy that benefits consumers.
Acadia Center examined the impact of adding battery storage (equivalent to Tesla’s Powerwall, a new battery system) and solar PV to homes in Connecticut, Hawaii, and Arizona to see what it would take to become independent from the grid. In all three states, going off-grid with a “right-sized” net-zero PV array (where a home’s demand for power approximately equals the energy it produces over a year) would be expensive. In New England, a very large number of batteries– 62 in Connecticut – would be needed to allow for year-round uninterrupted power off the grid. This is due to significantly lower winter PV production in the region and the resulting need for more batteries to store enough power to get a home through a long winter.
In sunnier and warmer climates with higher solar production in the winter, like Hawaii and Arizona, you would only need 40 and 42 batteries, respectively, to take a net zero home off-grid. But, average annual electric demand is higher in those states, so battery needs and cost would still be high when coupled with smaller solar PV arrays.
The least expensive path to an off-grid system is to oversize the solar PV array in order to reduce the number of batteries needed. (See chart and figure below.) Yet, while less costly, oversized solar arrays that are not connected to the grid essentially “waste” clean energy. In other words, once your demand is satisfied and the batteries are full, any excess energy that would otherwise be fed into the grid just dissipates. The Connecticut home with a 12.5 kW array may have reduced system costs, but it is now producing approximately 8,900 kWh per year more than it needs, and those kilowatt-hours are going unused. With a connection to the grid to use that otherwise wasted energy, the emissions reductions would be more than double what is achieved by only powering one home.
For a truly clean, efficient and affordable modern grid, customers should stay connected, and utilities should support that by avoiding discriminatory charges for solar customers and providing full and fair compensation for the unique value that rooftop solar generation provides to the grid. Cutting the cord will become less theoretical as solar plus storage systems continue to drop in price, but reducing overall emissions at the lowest cost and optimizing the function of the grid cannot be accomplished by going it alone. It may take a lot of counseling, but staying in a relationship with your utility is worth it in the long run.
System Size and Costs to be Grid Independent – Comparison of Net Zero & Optimally Sized (i.e. Lowest Cost) Systems in Connecticut, Hawaii, and Arizona
| Connecticut | Hawaii | Arizona | |
| Annual electric consumption | 6,656 kWh (555 kWh/month) | 10,520 kWh (750 kWh/month) | 7,957 kWh (663 kWh/month) |
| Net zero PV system size | 5.50 kW | 6.75 kW | 4.75 kW |
| Net zero annual PV production | 6,850 kWh | 10,726 kWh | 8,216 kWh |
| Net zero PV system cost | $19,250 | $23,625 | $16,625 |
| # of 10 kWh Batteries needed to go off grid | 62 | 40 | 42 |
| Battery costs | $217,000 | $140,000 | $147,000 |
| Total net zero off-grid cost | $236,250 | $163,625 | $163,625 |
| Optimal system size | 12.5 kW | 10.0 kW | 6.5 kW |
| Batteries needed for optimal system size | 7 | 5 | 4 |
| Optimal system cost | $68,250 | $52,500 | $36,750 |
| Optimal system PV array potential annual production | 15,567 kWh | 15,890 kWh | 11,243 kWh |
| Lost PV production with off-grid array | 8,920 kWh | 5,400 kWh | 3,300 kWh |
Battery Needs by PV System Size and Total System Costs to be Grid Independent in Connecticut
The Fine Print: Our assessment used a blend of Department of Energy’s hourly electric consumption models to represent a new, high-efficiency single family home in each location. The National Renewable Energy Laboratory’s PVWatts tool was used to simulate hourly electric generation in each of the homes for the various array sizes. At net zero, the PV array size was set so that generation was approximately equivalent to consumption on an annual basis. The battery storage was modeled so that there was sufficient storage and production to meet hourly demand for every hour of the year. No safety margin was included, nor were considerations made for degradation of storage capacity or whether instantaneous demands (such as an air conditioning unit’s start-up requirements) could be met. Costs of $3.50 per watt for PV and $3,500 for each 10 KWh of battery storage were used for determining optimum configurations. Additional storage system integration costs were not included.