Tesla Powerwall Can Increase Your Electric Bill

I have not bothered to run any numbers because we are on a straight rate pl an.

But if you are on a plan with cheap rates at night, you can install another hot water heater in series with your regular hot water heater, and put a t imer on the first hot water heater so that it only operates at night. So t he second hot water heater supplies you hot water just as it always has, bu t the water going into the heater is preheated on the cheap power during th e night.

When in Washington State, I was planning on doing that , but the politician s passed regulations which prohibited the power company from raising the da ytime rates. And that meant the rates at night were essentially the same a s the day rates.

Dan

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Where are you getting those insane numbers?!? The metering does not time ta g.

On a straight rate plan there is no disadvantage to batteries. The utility pays the same for KWH as they charge you. The batteries don't save you money but they do give you power during outages.

Well in California most people have gas water heaters so that plan won't work.

In my area, if you choose the time-of-use plan, the difference is pretty significant. So with solar you're trying to sell as many peak KWH hours as possible, you don't want to be using them to charge batteries.

You could wire up a system to charge batteries at night from low-cost KWH, connect your house to the battery during the day, and send all your solar output to the grid. This would be a rather complex installation and I'm not sure that the utility would sign off on it so you'd have to do it after the solar system is installed and not tell them.

When I was a kid they had two meters, one just for hot water. It cut off power to the water heater during the evening peak. Simple and effective. I don't know how they billed for it. Eventually they disconnected it though. Since they didn't do any rewiring I guess it was just running off the main meter and you received some fixed credit.

A friend had a thermostat that would duty cycle at peak times. I never understood how this would help the power company since the thermostat already duty cycles the furnace based on the temperature. Potentially this would prevent your furnace from keeping your home warm. When she got a new heat pump the installers didn't give here the Potomac Edison thermostat. I guess they won't be getting that back.

Why do the politicians in Wash state think a higher peak rate is a bad thing?

That is only true if they reimburse you for the distribution and transmission charges as well as generation. Here I'm pretty sure they only pay you the generation charge which is only about half the total cost. I can see the distribution charge applying in all cases, but clearly every watt you supply is a watt they don't pay transmission charges on.

Maybe I'm wrong about this. I don't have a solar setup. I recall this is what I got from the info the utility provided when Maryland passed the law which mandated them to buy your electricity.

That can also work for home heating if provisions are made. I've seen phase change material that helps to modulate temperatures through the day. This could be used to store heat from the utility at night at lower rates to warm the house during the day when rates would be higher.

A watt is a watt. It doesn't matter which power source supplies the house and which sends power back to the grid. Simplify, simplify, simplify...

This is what I'm talking about. These numbers are only generation, not including transmission or distribution.

"On June 9, 2011, the California Public Utilities Commission (CPUC) approved the Net Surplus Compensation rate based on current market prices, which is between $0.03 to $0.04 cents per kilowatt-hour (kWh). Payments to PG&E customers began on October 21, 2011."

When the batteries die, disposing of all those beasts will be interesting. They will be clogging the junkyards, alongside all the Teslas with dead batteries.

then there will be no point in using the Powerwall (if you have solar panels). The point of the Powerwall in conjunction with the solar panels is to (ideally) disconnect from the grid. During the day you use the solar panel, and the surplus is sent to the batteries, during the night your house is powered from the powerwall, so you don't have to get electricity from the grid.

Bye Jack

That link you gave is only if your solar system generates more KWH than you use over a 12 month period. You get paid real money for the excess

program pays you the fair market value for the balance of surplus electricity at the end of your 12-month billing cycle."

Net-metering has nothing to do with "fair market value."

The way net-metering works is that you are credited the baseline value of the KWH you put onto the grid. You then are charged the value of the KWH you take from the grid (which could be the baseline or could be more, based on your usage tier for the month).

For non-time-of-use, the value of the KWH you put onto the grid is the

PG&E) as long as you stay in the baseline tier.

For time-of-use, the value of the KWH you put onto the grid is based on

Some people think that they are banking KWH with the utility, but the reality is that you're banking the value of KWH with the utility, and with TOU metering the value varies.

Right now, during the summer, I am producing a lot more KWH than I'm

retail value of the KWH I'm sending to the grid. During the winter I'll be using the credit I've built up. If, at the end of 12 months, I have

the KWH were generated. But I won't likely have any credit left.

The goal is to size your solar system so that over 12 months you're just about at zero for total usage. You don't want a larger than necessary

The Powerwall or other battery system makes sense for a solar system that isn't tied to the grid. But other than for outage protection, it's a bad idea if you're tied to the grid, unless you install a more complex control system so you're not charging the batteries with high-value peak KWH.

That's true. But with TOU net-metering, the grid is a better place to store your excess solar energy than batteries.

it seems to me that the Powerwall would save you money even if you had no solar cell.

Charge the batteries during the night at off peak rates, use the batteries during the day when buying power would be at peak rates. No solar cells needed.

Dan

That is only if you generate more electricity than you consume over a 12 month period. If your solar system is too large then this is a possibility, but normally it would not occur.

With net-metering, you are credited the retail value of KWH you generate at the time you generate them. You use up your credits at the retail value of KWH at the time you consume them.

You get billed for electricity every 12 months. If, after 12 months, you haven't used up the retail value of your credits, you get paid only the wholesale value of the excess KWH you generated. If, after 12 months, you've used more than the retail value of your credits then you pay for whatever excess you've used at the retail value.

There is no year to year rollover of your retail credit, you start over every 12 months.

it depends. Here in Switzerland you earn very little (like one third of what you pay) for the energy you sell to the grid, so having the batteries it could be a good idea (I haven't done the math so not completely sure about that).

Bye Jack

Precisely.

You could put in even more batteries and sell excess back to the grid at peak rates.

But the batteries are so expensive that I doubt if you'd ever recover the cost of the batteries. The cost of storing excess off-peak power is something that utilities have been working on for a long time. The fixed cost, and the losses, make it uneconomical. Pumping water up to a reservoir during off-peak so they can use hydro during peak times is one thing they do.

What you could do, but what the utilities won't approve of, is to sign up for an EV (electric vehicle) rate plan where the off-peak KWH are even cheaper than a regular TOU rate plan, and charge extra batteries at night and use the electricity a peak times. You can't sell excess back to the grid on the EV rate plan. But with EV-B from PG&E you have two meters, one meter for the EV, and another at E1 or E6 which do offer net-metering. You could charge the battery at night from the EV meter and put it back on the grid through the E1 or E6 meter. They'd be really upset if you did this sort of thing.

You don't seem too be grasping what I am saying. You are billed for generation, transmission and distribution of all power that you use. The "Net Surplus Compensation" only compensates you for the generation charge. You still pay for transmission and distribution of the power you buy.

I guess the question is do they separate the surplus electricity from the "used" electricity or do they just subtract the two. The fact that the quoted text states a reimbursed rate says to me they are separate. So you buy electricity at some $0.14 per kwhr and sell it at $0.04 per kwhr.

Do you really only pay for electricity once a year?

Along with your Belchfire 2000s.

Here you get "credit" for what you send to the grid, and it's based on the retail value. However if, after 12 months, you have excess "credit" then you get paid only the wholesale value of the KWH you have generated. Fair enough, since the utility isn't interested in paying more than the wholesale cost for electricity no matter where they buy it.

This is for PG&E, the for-profit utility for most parts of northern California. Several cities have municipal, non-profit, utilities and the KWH rate they charge is far lower so solar makes no sense at all.

The city next to mine, Santa Clara, has municipally owned electric service. Their _highest_ KWH rate is much lower than PG&E's lowest KWH rate (other than the electric vehicle rate).

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Okay- I found that under TOU E-6 plan on their "tariff" page. They're prett y generous with that net generation. The only problem with your idea is tha t the PowerWall is fairly low capacity/peak delivery and will not be able t o handle the daytime peaks for long, if at all.

But, on a month to month basis, you are credited the cost of generation, transmission, and distribution of all the electricity you generate. You are credited the retail price per KWH which includes all of that. You don't get real money for that, you get a credit to use when you're not generating enough. Suffice it to say that PG&E isn't too happy about this system.

The net surplus compensation has nothing to do with your month to month usage. It's only paid in the unlikely event that over a 12 month period you generate more than you've consumed. The utility needs to sign off on the capacity of all new solar systems and they won't sign off on systems that are larger than needed to break-even. But no one would want to

You get full retail credit for what you put onto the grid, at the time you put it onto the grid, at the baseline rate (the lowest tier rate).

If you use more than you generate, over a 12 month period, you pay the full retail rate for the excess. If you generate more than you use, over

They credit you the same price they charge you for each KWH, for the time it is used (as long as you're in the baseline tier of KWH and they do subtract to determine the tier). If you're not generating enough to keep you in the baseline tier then you'd pay more for the KWH that were in a higher tier. But you'd be unlikely to be in a higher tier, even in the winter, with a properly sized solar system.

Yes. They send you a monthly bill that shows how much you've used and how much you may owe, but you only settle up once a year. My current amount is $2.21 after four months. But since my system went live during a time of greater than average production, I suspect that after 12 months I may owe a couple of hundred dollars.

The whole idea of time-of-use net metering is to move as much of your

PG&E has extremely high rates for electricity so if you're installing solar it makes sense to install a system large enough to offset your entire yearly usage.

PG&E doesn't like this system and is trying to get it eliminated. They correctly argue that solar owners are not paying for their share of grid maintenance. But the whole reason solar makes financial sense at all is the extremely high rates they are charging, especially in the higher usage tiers. Lower tier customers, even without solar, are also not paying their share of grid maintenance. They are going to change the tiers next years, going to two tiers instead of five tiers, with a much smaller difference between the tiers.

They already got rid of an even more favorable rate plan (E-7). But once they offer a rate plan, you're grandfathered in, even though the rates may change within that plan.

A good article on net metering here:

If net-metering goes away then battery systems like the Powerwall make sense.