TOU

Time Of Use Metering

By: Scott Carlson
Carlson Solar

Time of use metering is used by the electric companies to encourage users to use power at off peak times. Typically they charge a much higher rate for electricity during the middle of the day and early evening hours when power plants are producing at their maximum, while charging a much lower rate when power plants are running at a very low level of power generation.

This can be good or bad, depending on your particular situation. State law requires that the utility company must credit you for your extra power that goes backwards on to the grid, at the same rate, they were going to charge you for that power had you purchased it.

Therefore, if you put in a small solar electric system compared to your utility bill, and use a lot of electricity during the high peak times, you could theoretically end up with a higher electric bill, than before you had the solar system installed.

Conversely, if you are in a situation where you will not be using a lot of electricity during the high peak times, and your solar system is large enough to cover a good portion of your electric bill, you will be pushing power back and getting a higher credit for that electricity, allowing you to use even more electricity during the off peak times, when it is more cost-effective.

			Summer			Winter
			Peak Hours	Off Peak		Peak Hours	Off Peak
	SDG&E	M-F (12-6pm)	.15-.32	.15-.26		.13-.26	.13-.26
	SCE	M-F (10-6pm)	.36	.19		.21	.18

To be used for educational purposes only. Rate structure as understood on 2-26-07 by Scott Carlson and not verified by any independent source. Not to be used for financial evaluations.