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Depends on where you live. As of July 21, 2021, the cheapest Regular gas available in Sacramento, California, is $3.89, at Costco and Sam's Club. If you're not a member of either of those places, the cheapest regular at Arco and Fastrip is $4.01. The "name brand" stations, like Chevron, Union 76, Shell, and Exxon/Mobil are all charging $4.30 to $4.50/gallon. The overall average is about $4.25. Electricity in Sacramento costs 9.5¢/kW-hr between midnight and 06:00, if you arrange an EV charging discount from SMUD, our electric utility. So, let's compare on that basis. The Rav4 Prime in EV mode takes about 17 kW-hr to get a full charge from a 240v L2 charger - cost for that is $1.61, and the car can be driven about 43 miles in EV mode if the terrain is flat (it's a LOT less in hilly areas). So in EV mode, in summer, on flat terrain at 35 mph average on city streets, the car costs about 3.75¢/mile. At higher speeds, and in cold winter weather, the mileage and the battery capacity are about 10% less. Driving in Hybrid mode on gasoline, the car gets about 38 mpg. That's 425¢ worth of gasoline divided by 38 miles = 11.2¢/mile. Bottom line, if you live in California, where gas is crazy expensive, and electricity is cheap and EV charging is being subsidized by the utility company, it costs 3 times more to drive a Rav4 Prime on gasoline than it does on electricity. I don't call 300% a "marginal" difference.
I believe the point was that faster charging to allow more electric miles during the day is marginal if considering UPGRADE AFTER THE FACT. It is too bad Toyota did not just have 6.6KW OBC for all models.
 

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I believe the point was that faster charging to allow more electric miles during the day is marginal if considering UPGRADE AFTER THE FACT. It is too bad Toyota did not just have 6.6KW OBC for all models.
I agree. I doubt that the 6.6 kW charger costs Toyota more than couple of dollars more than the 3.3 kW charger, so it seems like they could have made it standard in all models. But there's this to consider too: It's a well known fact that fast-charging any battery potentially shortens it's life, compared to slower charging. I am left to wonder if the people who buy R4P XSE's with that 6.6 kW charger will ultimately end up having to replace the battery sooner than owners with 3.3 kW chargers in their Rav4 Primes?
 

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I agree. I doubt that the 6.6 kW charger costs Toyota more than couple of dollars more than the 3.3 kW charger, so it seems like they could have made it standard in all models. But there's this to consider too: It's a well known fact that fast-charging any battery potentially shortens it's life, compared to slower charging. I am left to wonder if the people who buy R4P XSE's with that 6.6 kW charger will ultimately end up having to replace the battery sooner than owners with 3.3 kW chargers in their Rav4 Primes?
Can you adjust the rate from the wall unit size? Or in the menu? I think I will stick with level 1 to trickle charge.
 

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I agree. I doubt that the 6.6 kW charger costs Toyota more than couple of dollars more than the 3.3 kW charger, so it seems like they could have made it standard in all models. But there's this to consider too: It's a well known fact that fast-charging any battery potentially shortens it's life, compared to slower charging. I am left to wonder if the people who buy R4P XSE's with that 6.6 kW charger will ultimately end up having to replace the battery sooner than owners with 3.3 kW chargers in their Rav4 Primes?
6.6 KW to a 17KWh battery is not fast charging. There is study that says charging at too slow a rate actually causes dentrites to form.
 

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Can you adjust the rate from the wall unit size? Or in the menu? I think I will stick with level 1 to trickle charge.
I don't think that the user can adjust the charge rate. On my Prius Prime, which has a 3.3 kW charger (probably the same one that's in the base model Rav4 Prime), there are two modes, and which one is used is determined automatically by the battery management computer, according to the voltage of the power source: 1. If the car is plugged into a 120 volt (L1) supply, the charger will attempt to draw 13 amps from the circuit. This is about the maximum that can be drawn continuously over an extended period of several hours, without heating a 15 amp circuit breaker or fuse to the point where it might pop in a slight surge or ripple appears in the circuit. Most 120 volt outlets in your home are fed through 15 amp circuits. 13 amps at 120 volts = 1,560 watts, about as much as an electric bathroom heater or microwave oven on full power, and it takes about 5-1/2 hours to charge the 8 kW-hr battery in my Prius Prime with the L1 charger that came with the car. The much larger Rav4 Prime battery probably tales at least 11 hours to charge on a 120 volt circuit. 2. If the charger detects 240 volts incoming, i.e. an L2 charger, it will still limit itself to 13 amps (3,300 watts) to prevent tripping a 15 amp circuit breaker if that's what the supply circuit is equipped with. Now, it is possible to buy an L2 charger that can deliver 27 amps (6,600 watts) - you can find them on Amazon for about $350 - but these won't do you any good on a Prius Prime or Rav4 Prime that has only a 3,300 watt charger. The 3,300 watt charger will not draw more than 13 amps even if supplied from a 30 amp or 40 amp L2 charging station. I've proved this on my Prius Prime: there are public 30 amp and 40 amp L2 charging stations at the SMUD Headquarters building, but my Prius Prime still takes 2 hours to charge, same as with my 13 amp L2 charger at home. A 30 amp L2 charger will only actually benefit you if you buy a Rav4 Prime XSE with the Premium package and the 6,600 watt charger, or a car like a Tesla or a Chrysler Pacifica, that has a 6,600 watt charger as standard equipment.

NOTE: If you need to use an extension cord with the L1 charger that came with your car, this can be done if you are careful to observe the following: Use a 10-gauge copper-conductor extension ONLY, !2 Gauge extension cords, or cheap aluminum conductor ones, will get hot and cause too much voltage loss. NEVER use an extension cord, even a 10 gauge one, that's longer than 25 feet. The prongs on the extension cord connectors must be clean and not corroded. If the connectors or the cord feel unusually warm after 10 minutes, stop - there is too much resistance and therefore too much voltage loss. I've used a 10 gauge, 25' extension cord a couple of times with no problem, when when I couldn't park close enough to an outlet to reach it without using a short extension cord. Toyota does not recommend using an extension cord at all, so I would only do it in emergencies and not make it a regular thing.

As for the relative risks of "quick charging" vs slow charging, I've almost always charged my Prius Prime on 240 volt L2 chargers, and it's showed no sign of battery degradation in the two years/16,000 miles I've owned it. The battery is actually doing BETTER now than it did when I first bought the car. In the first 12 months, it was only giving me 30 miles of range. In the second 12 months, it's giving me about 33 miles in winter (average temp 45°F), and 37 miles in summer (average temp 90°F). So the use of a 240 volt, 3,300 watt charger doesn't seem to be hurting it any.
 

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I don't think that the user can adjust the charge rate. On my Prius Prime, which has a 3.3 kW charger (probably the same one that's in the base model Rav4 Prime), there are two modes, and which one is used is determined automatically by the battery management computer, according to the voltage of the power source: 1. If the car is plugged into a 120 volt (L1) supply, the charger will attempt to draw 13 amps from the circuit. This is about the maximum that can be drawn continuously over an extended period of several hours, without heating a 15 amp circuit breaker or fuse to the point where it might pop in a slight surge or ripple appears in the circuit. Most 120 volt outlets in your home are fed through 15 amp circuits. 13 amps at 120 volts = 1,560 watts, about as much as an electric bathroom heater or microwave oven on full power, and it takes about 5-1/2 hours to charge the 8 kW-hr battery in my Prius Prime with the L1 charger that came with the car. The much larger Rav4 Prime battery probably tales at least 11 hours to charge on a 120 volt circuit. 2. If the charger detects 240 volts incoming, i.e. an L2 charger, it will still limit itself to 13 amps (3,300 watts) to prevent tripping a 15 amp circuit breaker if that's what the supply circuit is equipped with. Now, it is possible to buy an L2 charger that can deliver 27 amps (6,600 watts) - you can find them on Amazon for about $350 - but these won't do you any good on a Prius Prime or Rav4 Prime that has only a 3,300 watt charger. The 3,300 watt charger will not draw more than 13 amps even if supplied from a 30 amp or 40 amp L2 charging station. I've proved this on my Prius Prime: there are public 30 amp and 40 amp L2 charging stations at the SMUD Headquarters building, but my Prius Prime still takes 2 hours to charge, same as with my 13 amp L2 charger at home. A 30 amp L2 charger will only actually benefit you if you buy a Rav4 Prime XSE with the Premium package and the 6,600 watt charger, or a car like a Tesla or a Chrysler Pacifica, that has a 6,600 watt charger as standard equipment.

NOTE: If you need to use an extension cord with the L1 charger that came with your car, this can be done if you are careful to observe the following: Use a 10-gauge copper-conductor extension ONLY, !2 Gauge extension cords, or cheap aluminum conductor ones, will get hot and cause too much voltage loss. NEVER use an extension cord, even a 10 gauge one, that's longer than 25 feet. The prongs on the extension cord connectors must be clean and not corroded. If the connectors or the cord feel unusually warm after 10 minutes, stop - there is too much resistance and therefore too much voltage loss. I've used a 10 gauge, 25' extension cord a couple of times with no problem, when when I couldn't park close enough to an outlet to reach it without using a short extension cord. Toyota does not recommend using an extension cord at all, so I would only do it in emergencies and not make it a regular thing.

As for the relative risks of "quick charging" vs slow charging, I've almost always charged my Prius Prime on 240 volt L2 chargers, and it's showed no sign of battery degradation in the two years/16,000 miles I've owned it. The battery is actually doing BETTER now than it did when I first bought the car. In the first 12 months, it was only giving me 30 miles of range. In the second 12 months, it's giving me about 33 miles in winter (average temp 45°F), and 37 miles in summer (average temp 90°F). So the use of a 240 volt, 3,300 watt charger doesn't seem to be hurting it any.
Thx for the detailed explanation. For some reason, Toyota included 6.6kw chargers for all trims in Canada, but I don’t plan to install L2 charger anyway, just going to charge at 110v. Your Prius sounds amazing. I hope my rav4, once I got it, would do the same and last a long time.
 

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The EVSE and the charger on the car negotiate the charge rate when it is plugged in. The charge rate used is the lower of the available rate on either the EVSE or charger. So if you have a Rav4P with a 3.3kW charger, it will never charge above 3.3kW no matter how much the EVSE can supply. There are EVSE's available that allow setting the charge rate on them. Using one of these, you could limit the charge rate to 2kW for example by telling the EVSE to supply only 2kW. During the negotiation phase, the car and EVSE will determine that 2kW is the lower level and the charging will proceed at that rate. Usually the values are specified in amps but the effect is the same since the voltage is fixed.

Battery degradation from charging or discharging is usually expressed in C-rate. This is a ratio of the charge/discharge rate vs the total capacity of the battery. So a 200kWh Tesla battery charging at 20kW is using a C-rate of 0.1 (20/200). Charging a 40kWh Leaf battery at 20kW is a C-rate of 0.5. Higher C-rates do stress the battery more but it is more complicated than just saying X kW is good and y kW is harmful. It depends on the capacity of the battery. This applies to both charging and dis-charging.
 

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Thx for the detailed explanation. For some reason, Toyota included 6.6kw chargers for all trims in Canada, but I don’t plan to install L2 charger anyway, just going to charge at 110v. Your Prius sounds amazing. I hope my rav4, once I got it, would do the same and last a long time.
What I've heard about the fact that all R4P's in Canada having the 6.6 kW charger: Because of the longer winters and colder average temperatures, compared to the US, plug-in hybrids of all makes have to use a lot more of the incoming power during a charge cycle to run the battery heater, and the cabin heater if the owner is sitting in the vehicle during the charge with "My Room" mode activated. If you have the "My Room" mode turned on and are running the heater or the air conditioner, this will siphon off nearly 1/3 of the charge current on a 3.3 kW charger, greatly increasing the charging time, so Toyota mitigated the problem by giving all Canadian R4P's the 6.6 kW charger. Running the heater or a/c in "My Room" mode with the 6.6 kW charger only adds about 30 minutes to the charge time instead of 90 minutes longer charging with the 3.3 kW charger. I think Canadian and Alaskan R4P's may also have a more powerful battery heating grid than the cars bound for the lower 48 and Hawaii, and this would also siphon off too much charging power and extend charging time if the cars had the 3.3 kW charger. The L1 chargers are fine, if the 10 hour charging time isn't an issue for you. Where I live, that would be a small problem: My electric utility only gives me the EV charging discount between Midnight and 06:00 in the morning, so if it took 10 hours to charge the car, I would be paying the non-discounted "regular" rate for 4 hours of the charge cycle. I bought an L2 charger with a NEMA 10-30 plug for my Prius Prime: this plug fits the existing 240 volt wall outlet in my garage that was intended for an electric clothes dryer. My dryer is gas, so I wasn't using the outlet, and dedicating it to charging the Prius saved me the cost of having an electrician install a new 240 volt circuit and outlet in the garage for the car charger.
 

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The EVSE and the charger on the car negotiate the charge rate when it is plugged in. The charge rate used is the lower of the available rate on either the EVSE or charger. So if you have a Rav4P with a 3.3kW charger, it will never charge above 3.3kW no matter how much the EVSE can supply. There are EVSE's available that allow setting the charge rate on them. Using one of these, you could limit the charge rate to 2kW for example by telling the EVSE to supply only 2kW. During the negotiation phase, the car and EVSE will determine that 2kW is the lower level and the charging will proceed at that rate. Usually the values are specified in amps but the effect is the same since the voltage is fixed.

Battery degradation from charging or discharging is usually expressed in C-rate. This is a ratio of the charge/discharge rate vs the total capacity of the battery. So a 200kWh Tesla battery charging at 20kW is using a C-rate of 0.1 (20/200). Charging a 40kWh Leaf battery at 20kW is a C-rate of 0.5. Higher C-rates do stress the battery more but it is more complicated than just saying X kW is good and y kW is harmful. It depends on the capacity of the battery. This applies to both charging and dis-charging.
Thanks! I didn't know that the car and the charging stations "talk" to each other to set an appropriate level of charge current. I can why this would be necessary, as there are public charging stations that can supply 7,200 watts (240 volts, 40 amps), whereas a car like the Prius Prime isn't designed to accept anything higher than 13 amps (3,300 watts).
 

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If you sized your pannels correctly, you should have excess capacity. If you didn't you'll probably have to add a pannel or two.

However, reality wise, most people will probably be doing the majority of their charging at night, when the solar panels aren't producing electricity. Also, many electric providers have cheaper rates at night. Some electric providers allow you to get a dedicated EV meter and rock bottom kW rates.
My utility gives me .05 rebate per kwh for charging between 11 pm and 6 am
 
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