Throughput is defined as the energy moved through the battery during each roundtrip discharge/charge cycle.

To calculate the length of the warranty period we multiply our daily discharge by 365 to determine annual kWh discharge then divide half of 37,000 kWh by that number. While the Tesla battery is a stand-alone storage solution, we’re evaluating it here as an addition to a new solar system. So how do you decide which rate plan is best for you? We derive the following detailed average hourly kWh usage from SCE collected data: At SCE summer/winter tiered rates, our customer’s daily power bill comes to $7.03 or an average monthly bill of $213.78. Here are the choices from Southern California Edison. This article discusses the potential benefits for homeowners wanting to install grid-interactive solar-plus-storage operating under Southern California Edison’s new time-of-use (TOU) rates. Our goal is to charge our customer’s Tesla Powerwall mid-day between 8 a.m. and 4 p.m. while rates are 13-cents/kWh and solar production is at its highest.

What is the anticipated Tesla battery warranty life based on this use? SCE Peak Hours. We analyze whether choosing to store and shift energy (using a Tesla Powerwall 2 Li-ion battery) under a TOU rate plan provides any economic benefit. Detailed load analysis will make decisions regarding energy storage and solar system sizing a straightforward economic analysis, rather than a guessing game. TOU-D-5-8PM: Even higher on-peak rate of $0.47 from 5-8 PM on weekdays, but peak time is only 3 hours. Visit for more information. SCE Rate Main features; TOU-D-4-9PM: On-peak rate of $0.37 from 4-9 PM on weekdays. To determine the cost of energy from the battery in $/kWh we need to analyze energy throughput. Let’s assume our customer has the average load profile we found on the SCE website. Or, use their rate comparison tool. The daily weighted average rate becomes $0.178/kWh. To learn more about SCE’s new rate structure or for questions, call Hot Purple Energy (760) 322-4433 to speak to a representative. This delivers a benefit of $35.88/month, which amounts to a 16.8% decrease in energy cost over the tiered rate cost and a 15.1% decrease from TOU rates with no arbitrage. We analyze whether choosing to store and shift energy (using a Tesla Powerwall 2 Li-ion battery) under a TOU rate plan provides any economic benefit. Sending a letter with your account information to SCE stating your intention to remain on your current tiered rate structure. Assuming $0.08/kWh payment for exported energy, this solution would average on a monthly basis: This analysis based on the SCE average residential load profile shows that power arbitrage using energy storage is not economical without financial subsidies beyond the federal ITC anticipated here. SCE’s justification for doing this is that the cost to deliver power has changed. Right now, the most expensive electricity Edison will sell is at $0.47 per watt between 2 PM and 8 PM. Usually more can be saved by installing solar panels. This article discusses the potential benefits for homeowners wanting to install grid-interactive solar-plus-storage operating under Southern California Edison’s new time-of-use (TOU) rates. That means solar customers will be charged more for energy at that time and will be credited less when the panels are at peak performance. Daytime usage: 8 a.m. – 4 p.m. = 10.726 kWh, Nighttime usage: 9 p.m. – 8 a.m. = 10.726 kWh, Self-supply during daylight of 342 kWh at 8-cents/kWh, Directly offset 33.2% of customer daily energy needs, Offset 60% of customer energy costs or $1,539/year, Attain a positive ROI in less than 8 years. How much energy is used between 4 p.m. and 9 p.m. measured in kWh? Any export above daytime load requirement will be paid at a slightly reduced rate to the stated TOU daytime rate but is a positive benefit in reducing the customer’s electric bill. For a customer with solar, then the DR-SES plan will be the best because it moves peak hours into the daytime such that more of your excess solar power during the day will attract a … For non-solar SCE customers, who already pay more for their energy, the numbers bear out a little differently. If you cannot install solar, TOU-DR-P will be the cheaper plan provided you can limit your use of power on high use days. Our Tesla Powerwall lifetime ROI is calculated as 4.64 years at $35.88/month which nets a $1,997.80 energy savings minus the original $6,020 Tesla battery purchase, or a negative 4.6-year ROI of $4,042.20. Bookmark, share and interact with the leading solar construction magazine today. Get the ball rolling now and learn how you can save. In our example, the residence receives service from SCE that offers residential 2-tier TOU rates, as shown in Figure 2. Once charged, we’ll set the Tesla Powerwall clock to disconnect the customer from the utility at 4 p.m. and remain disconnected until 9 p.m. during which time we’ll operate our loads using battery-supplied power, assuming the batteries can handle peak demand. I would say there really isn’t any difference between the two except for the source of energy charging the battery. While the new rate structure may extend the ROI period slightly, it will still provide an attractive investment to potential solar customers. Right now, Monday through Friday 2-8 PM are SCE’s peak hours. This is not to say that the battery will no longer function out of warranty. Domestic (Default) TOU-D (A) TOU-D (B) TOU-D-T. Rate plans are complicated, and they tend to change every few months. What is the battery throughput and $/kWh rate? Unit C-3, Calabasas, CA 91302, What SCE Net Metering 2.0 Means for Solar, 4 Questions Everyone's Asking About the Solar Tax Credit, Three Reasons for Businesses to Go Solar This Year, How California's Solar Battery Backup Incentive Saves You Money. SCE will have several TOU rate options: TOU-D Prime, TOU-D Option 4-9, and TOU-D Option 5-8. While this large shift in TOU rates will have a negative impact on current solar value and slightly decrease the length of ROI, SCE is projecting a rate increase in which the cost of “off-peak” rates will likely go up in the next year and the cost of “on peak” rates will come down making solar more attractive than it may seem now. Knowing how you use electricity will help you identify additional ways to save money on your electric rates. New Rate . Power arbitrage benefits utility operations. After March 1st, Edison will move new solar customers to a Time of Use Plan and change its peak period to 4 PM to 9 PM. [SCE will] deduct the energy you export to the grid at times when generation exceeds on-site demand from your bill, and you may even earn surplus credits for the energy you produce.”. From this we get an average monthly bill of $177.90. Under TOU rate plans, rates will vary depending on the time of day. Right now, Monday through Friday 2-8 PM are SCE’s peak hours. The solar system size can, on average, charge the battery and cover daytime loads for our customer. Since this recharge power is energy we would otherwise export, we need to include it in the cost of battery energy. The assumptions made on the Tesla Powerwall Warranty battery life are not accurate. The Public Utilities Commission has approved SCE, and other major California utilities, to make a shift in the Time of Use (TOU) rate plans starting March of 2019. Solar customers generate energy, sell it to the utility, and make the highest amount of money that the utility offers. Box 800 That means the most expensive energy is coming into your home when your solar panels have stopped working for the day. Browse the current issue and archived issues of Solar Power World in an easy-to-use, high-quality format. The simple ROI occurs in 14 years. When your solar panels overproduce, they also buy that power at a higher rate. SCE For Time of Use 2018 or SCE Time of Use rate comparisons, see Southern California Edison’s website. If these are different from Tesla’s viewpoint it appears they represent a combination of applications. All Rights Reserved. About Intelligent Design Solar You sell a lot of that excess electricity back to Edison at $0.47 per watt. Our customer has an insignificant ($4.26/month) financial benefit from moving to a TOU rate structure, without investing in energy storage or changing usage patterns. SCE's best TOU plan for people with EV is .15 off peak and .41 on peak. Hot Purple Energy Now a Tesla Powerwall Installer. The equation is: Recharge is at the solar avoided cost of $0.08/kWh.

In addition, SCE’s shift in TOU will cause majority of Solar’s overproduction to be discounted.

However, under the new rate schedule, SCE has shifted the “on peak” time and the majority of solar production will now fall under “off-peak” hours and only be credited at $0.15 per kWh for overproduction (TOU-D-Prime). Tesla could then argue the 37 MWh throughput condition applies. The Powerwall Limited Warranty ( explicitly states that when operated solely in time based control mode the Powerwall can perform unlimited cycles and will have 70% energy retention at year 10. The customer will have to decide whether they can expect useful life beyond the battery warranty and I would strongly suggest they get clarification from Tesla on their interpretation of the Warranty conditions. The equation is: Daily discharge rate multiplied by cost per kWh gives us our daily power cost from batteries. Southern California Edison is about to make a big change in the way it charges its customers, and it will have a huge effect on the economics of adding solar to their homes. *We never share your information with other vendors or solar companies. When your solar panels overproduce, they also buy that power at a higher rate. Also, watch this video on Time of Use. Tier 1 is .19. To understand how this will affect you, let’s get clear on two terms. By Todd Pistorese, CEO, Intelligent Design Solar, This is a complementary article to the previously published Case study: When solar+storage operating in time-of-use arbitrage mode beats the economics of standalone solar by Adam Gerza, COO of Energy Toolbase. That’s great for solar customers, because those are hours when your solar panels producing the most, and it’s a time when a lot of people aren’t home. To have the system installed by March 1st, you’ll need to purchase by around mid-December. A 7-kW solar system without storage has a levelized 25-year installed cost of approximately $0.08/kWh. Now is the time to put a high efficiency SunPower system on your house and be grandfathered into the current rate structure for 5 years. And the power that you sell to them in the middle of the day will now only be worth $0.22 per watt. On Peak is between 4-9pm 4-9pm is when my wife and I use most of the electricity.