The PG&E Energy Statement comes every month and it is a major slice of our annual expenses. Dissecting the utility bill while solving for ‘X’ may provide some clarity.

Constants (known assumptions)

• kWh == kilowatt hours – a measure of energy consumption
• Well #3 produces 1,792 GPM at a consumption rate of 169 kW
• Well #2  produces  780 GPM at a consumption rate of 77 kW
• Booster has a consumption rate of 41 kW
• Booster Pump must be run during operation of either well.
• 325,851 gallons == 1 acre foot

Rates for Energy Charge (reference the PG&E document: Large Time of Use Agricultural Power – Schedule AG5B )
Summer
Peak:            $0.20775 12:00 noon to 6:00 p.m. Monday through Friday
Off-Peak:       $0.08974
Winter
Partial-Peak:  $0.10984 8:30 a.m. to 9:30 p.m. Monday through Friday
Off-Peak:       $0.08143

Calculations showing my arithmetic
1792 gpm * 60 min = 107,520 gal/hr so 325,851 / 107,520 = 3.03 hrs to produce 1 acre foot
780 gpm * 60 min =   46,800 gal/hr so 325,851 /  46,800 = 6.962 hrs to produce 1 acre foot

Billing breakdown explanation
There are primarily three types of charges on an electric bill: fixed charges, energy charges and demand charges.

• Fixed Charges are usually small fees that do not change from month to month. ~$40/month
• Energy Charges is based on the amount of electricity in kilowatt-hours (kWh) consumed over the entire billing cycle and vary depending on time of use.
• The amount of electricity being consumed at any single moment is known as Demand (kilowatts).  Demand Charge is a calculation using the maximum energy consumption flow rate seen during the billing period.  For each 15-minute period in a billing cycle, the average demand is calculated. Typically, a motor startup will result in this peak flow rate value but the average over the 15 time interval helps to mitigate somewhat. The utility billing amount for Max Demand is $5.95 and Well #3 has a typical Max Demand of 168 kWh so the product of the 2 would be $1,000.00

Billing summary based upon actual averages
All of this boils down to real world average billed costs (including meter charges, demand charges, etc.) of:
$0.13 kWh  for Well #2
$0.20 kWh for Well #3
$0.12 kWh for the Booster Pump

Usage sample (July / August )
Well #3 running for 3.03 hours produces 1 acre foot of water with an energy usage of 512 KWh with the Booster Pump using 125 KWH for a total of 637 KWh. Cost per acre foot == $117.40 ((512 x .20) + (125 x .12))

Well #2 running for 6.962 hours produces 1 acre foot of water with an energy usage of  536 KWh with the Booster Pump (req’d) using 285 KWH for a total of 821 KWh. Cost per acre foot == $205.25 (821 x .25)

 Takeaway after solving for X

1. Turning on a well when irrigation is not planned as if only to fill a truck water tank or perform a well test would cost a grand just to throw the switch! See the PG&E service period 11/17/2015 to 12/15/2015 and also PG&E service period 1/15/2016 to 2/16/2016 for Well #2
2. Well #3 is the more efficient. This Well uses more energy as it is throwing more water (working harder) but it takes less time to get to the finish line.
3. Off Peak usage is much cheaper. During some summer months the Well(s) must run ’round the clock so the ability to take advantage of rate incentives is limited.

Apologies if you found that topic to be DRY (and sorry for the pun), but water is a critical ingredient for we farmers. I promise future articles on this important resource.