what is the point of net-metering (VA)

mshen11

http://www.dsireusa.org/incentives/incentive.cfm?Incentive_Code=VA02R&re=1&ee=1

Virginia's net-metering law applies to residential generating systems up to 10 kilowatts (kW) in capacity and non-residential systems up to 500 kW in capacity. Net metering is available on a first-come, first-served basis until the rated generating capacity owned and operated by customer-generators reaches 1% of an electric distribution company's adjusted Virginia peak-load forecast for the previous year. Net metering is available to customers of investor-owned utilities and electric cooperatives, but not to customers of municipal utilities.

Net metered energy is measured by a meter capable of gauging (but not necessarily displaying) power flow in both directions. Monthly net excess generation (NEG) is carried forward to the next month. At the end of each 12-month period, the customer has the option of carrying forward eligible excess NEG to the next net metering 12-month period or selling the NEG to the utility. The amount of credit to be carried forward to a subsequent net metering period may not exceed the amount of energy purchased during the previous annual period.* In the case of selling the NEG to the utility, the customer must submit a written request to establish a power purchase agreement with the utility prior to the beginning of the net metering period. The investor-owned utility must pay a price equaling the PJM Interconnection LLC (PJM) zonal day-ahead annual, simple average locational marginal price for the previous year and in proper PJM load zone (this information is published by the PJM Market Monitoring Unit) or a mutually agreed upon higher price.

Systems must comply with the National Electrical Code Article 690, Institute of Electrical and Electronic Engineers (IEEE) Standard 1547 (July 2003), and Underwriters Laboratories (UL) standards. Utilities may require (and usually do require) an external, lockable disconnect switch at their expense.

Recently, in April 2009, the Governor signed legislation (HB 2155) making changes to net metering in Virginia. System size caps for net metering were not changed, but HB 2155 allows utilities to approve a higher capacity limit at their discretion. The bill also permits customers that are served on time-of-use tariffs to participate in net metering. Finally, the bill addresses ownership of renewable energy certificates. It specifies that the customer-generators own the RECs associated with their renewable electrical generating facility, and at the time that a customer enters into a power purchase agreement with the utility, the customer has a one-time option to sell RECs to the utility. This provision does not preclude the customer and utility from voluntarily entering into an agreement for the sale and purchase of excess electricity or RECs at any other time. The SCC must issue regulations implementing HB 2155.

* For example, if a customer-generator bought 1,500 kilowatt-hours (kWh) from a utility during the first 11 months of the annual period, and then generated 2,000 kWh of excess electricity in the 12th month, the customer could carry forward 1,500 kWh to the following month, and the remaining 500 kWh would be granted to the utility.






i read the above as following: if you generate enough electricity so that you dont rely on the grid (and have excess), the excess is a free gift to the power company - because your purchase is $0, therefore you carry over to the next year $0, the remaining excess is "granted" to the utility

BB.

Re: what is the point of net-metering (VA)

mshen11 wrote: »

i read the above as following: if you generate enough electricity so that you dont rely on the grid (and have excess), the excess is a free gift to the power company - because your purchase is $0, therefore you carry over to the next year $0, the remaining excess is "granted" to the utility

Yes--you have it correct. The utility does not really like Net Metering and the law is setup for you to generate exactly your needs and the loss of power is a "gift" to the utility or a penalty to you to not oversize your array and become a "for profit" small power generator.

If the utility where approaching solar as a true business, they would pay you between 5% to 50% of your retail bill as this is the "True Cost" of their power--the rest is distribution charges, spinning standby, and profit for the company.

-Bill

tallgirl

Re: what is the point of net-metering (VA)

Tariffs, such as VA's, point out why battery-backed, grid-interactive inverters are a much better investment than pure grid-tie inverters.

With battery backed inverters the meter can be made to spin backwards much less.

Solar Guppy

Re: what is the point of net-metering (VA)

TG, can you show us a break down where a battery based GT system is more cost effective than a non-battery based GT system, I have never heard of this before.

Even in the OP posted example, it would require a PV system that can generate more than the home uses in a month, very unlikely that a system less than 10kw system could do that for a typical US home. And even then, only about 50 dollars of electric would be gifted each year for the ability to have net metering and generating more than the home uses.

I have 14kw on my home and I barely net-out over a year, this is with R40 insulation, all energy efficient appliances and a new SEER 16 Heat pump system

From what I have read Battery based is over 1 dollar watts where pure gridtie is closer to 25 cent watt, even lower for example if you state has rebates and then the federal 30% tax credit. My recent 8kw I just added will have a pay back of about 4 years.

Cariboocoot

Re: what is the point of net-metering (VA)

I think what she's saying is that in a case where you have to give away your "excess" power production to the utility it is better to have a big battery bank and store it - "keeping it for yourself" so to speak. You could then draw off it at night and still not use the utility's power.

Of course this is essentially going off-grid, but maintaining the grid connection for those times when you don't have enough solar.

If the utility will not pay you for power, what's the sense in having the G-T install?

BB.

Re: what is the point of net-metering (VA)

I don't believe that Hybrid (GT+Off-Grid capable battery based) Systems are a good deal vs normal 1 year net metering...

I did a back of the envelope calculation here about 1 year ago--and the cost of an Inverter (hybrid or off-grid + AC charger + batteries + replacement every 10 years or so)--the costs to run such a system (charge at night, provide power during the day) was much closer to $0.45 per kWhr--that was based on 20 year life, simply divided into the cost of the system and maintenance (based on internet pricing, ignoring taxes, interest, present value/future worth, installation and permit costs, etc.)...

Such a system would not save me any money (buy at $0.09+$0.45 per kWhr at night, "sell" power at $0.30 per kWhr during summer weekday afternoons).

Add solar panels, bump the costs up even more.

A hybrid system can make sense for people that have a lot of outages (storms, etc.) as an alternative to generator backed AC power.

Batteries on a Grid Tied / Net Metered system will last longer because they are not cycled and the bank can be smaller (as it is for emergency use only--and who cares if it discharges to 50% once or twice per year).

If you start to cycle the battery bank every day--you will need a larger bank (or accept shorter life) and substantially decrease your battery bank life (and increase costs). And the size of your battery bank is going to define how many days you can offset your power usage. And--for most people they will only be able to offset their power by 3 days or so... With 1 Year Net Metering, I can offset my power (summer lots of energy) to my poor generation periods (winter clouds). And, I can even offset power I have not even generated yet (my net metering period begins in October, and I can "go negative" in deep winter, and yet get "positive" in my account by the time spring/summer rolls around).

And I am using Time of Use Metering--my week day Noon to 6pm summer (six month) period--I sell power at $0.30 per kWhr and by it back at night at $0.09 per kWhr)... Basically a 3x increase in array "output" (during summer peaks) because of TOU billing.

Having a Hybrid/Battery based system just does not have ability to do any of these financial offsets.

For people that don't have net metering available to them--it is very difficult to design a cost effective solar RE system. Looking at solar thermal (hot water, heating, etc.) systems will probably offer a better return on investment vs any Hybrid/off-Grid solar PV system.

Will there be better/smaller/cheaper home battery technology in the future--possibly--but not at this time.

-Bill