Residential Solar Applications

How Electricity Is Sold From SDG&E For Residential Use
Electricity is sold in tiers in San Diego County. Tier one is the cheapest portion of your electrical bill. It is around 350 kilowatt hour per month. This amount varies around the county and varies as to the time of year.

Here is an example of a tier charged SDG&E electrical bill for the following residential solar project example. These unit prices are from adding your kWh cost with electric energy charge cost.

Example’s total electrical cost for the amount of $310.33 for 1,247 kWh

Tier 1: first 345 kWh called “baseline” 342 kWh x $0.12557 = $42.94494
Tier 2: 101% - 130% of baseline amount = 103 kWh x $0.14677 = $15.11731
Tier 3: 131% - 200 % of baseline amount = 239 kWh x $0.26455 = $63.22745
Tier 4: over 200% of baseline amount = 563 kWh x $0.32521 = $183.09

DWR bond charge = 1,247 kWh x $0.00477 = $5.95
Total electrical charge = $310.33

As one can see, the more you use, the higher one is charged. So it is most cost efficient to eliminate your upper 3 tiers of use by designing a solar system that will produce the amount a house uses a year in the upper 3 tiers. The following example was designed to eliminate the upper 3 tiers of use.

Example System:
The residence uses 12,395 kilowatt hours per year.
This system is sized to reduce the upper 3 tiers of electrical use / charges.
System size is 4200 watt PTC DC system which consists of 24-175 watt Solar World panels and one 4000 watt SMA inverter. The systems yearly production is estimated at 7,155.00 kilowatt hours. ( Please note every house is priced different )

Cost of system: $24,075.00
Rebate: $5,590.00
Federal tax credit: $7,222.00
System cost 1st year: $11,263.00

Electrical Cost Savings
Savings on 4200 STC watt system is based on $.26 per kWh with a 7% increase per year.
In 2008 SDG&E’s increase was about 8%.

Cost of kWh = $0.26 average
Yearly system output in kWh =7,155.00