Calculating and understanding grow room electricity use and rate plans to keep the cost manageable.
When setting up a grow room, you need to understand your costs. Electricity will be one of your largest bills.
Utility companies calculate their electric rates based on kilowatts used per hour (kw/hr).
One Kilowatt Hour = 1000 watts used for 1 hour
A 1000 Watt HID light running for an hour uses 1 kw/hr. The same light running for 12 hours a day will use 12kw/hrs per day and about 360kw/hrs each month.
The first step to estimating your future grow room’s electric bill, is to estimate the electric consumption. Start listing the amount of watts that each piece of equipment will draw and multiply it by the number of hours a day that it will be running. Lights will likely run for either 12 or 18 hours a day, but fans, reservoir heaters and other equipment may run 24 hours a day or possibly only for a few minutes. For example, if you have six 1000 Watt HID lights operating during the vegetative state, the calculation of your monthly draw from your lights would look like this:
6 lights x 1000 Watts x 12 hours x 30 days = 2,160,000 Watts or 2160 kw
Once you have added up all the hours of electrical consumption per day, you will have the kw/hrs used per day. Now multiply this by the number of days in the month. This should give you the total kw/hrs of electricity your grow room will use each month. Now add your grow room’s total kw/hr to the kw/hr used by the rest of the residence. If you are planning a future grow room, simply look at your last utility bill and find the number of kw/hr you currently use and add this to your future use. It is important to add both existing and future use because the total is going to be charged a rate based on a consumption tiered scale as you will see below.
Residential Rate Charges
PG&E Residential rates are based on the region you live in and the amount of electricity that you use. There are also voluntary programs like the E7 that additionally take into consideration the time of day the power is used.
To find the rates for your region you will have to call your utility company or visit the rate section of their web page. Here is the link to the residential electric rates for PG&E.
PG&E charges a standard rate for what they consider the “normal use” of electricity per month called a “baseline quantity”. The baseline quantity can change depending on the region you live in, the time of year, and whether or not your house is heated with electricity or gas. The size of the home, the number of occupants and the consumption of an average home are not considered. For my home on California’s central coast the baselines are as follows.
Assuming an electric heated home:
Winter, November through April – 16.8 kw/hr per day
Summer, May through October – 9.1 kw/hr per day
Assuming a gas/propane or wood heated home:
Winter, November through April – 9.1 kw/hr per day
Summer, May through October – 7.5 kw/hr per day
Because you are billed monthly, the baseline kw/hrs per day are multiplied by the number of days in the month to calculate your monthly baseline allowance.
If I stay at or below my baseline allowance my standard rate is 12.223 cents per kw/hr.
Watch what happens to my rates if I go over my baseline.
Tier 1 – Up to 100% of Baseline – 12.223 cents per kw/hr
Tier 2 – 101% to 130% – 13.907 cents per kw/hr
Tier 3 – 131% to 200% – 29.276 cents per kw/hr
Tier 4 – 201% to 300% – 33.276 cents per kw/hr
Tier 5 – 300% + – 33.276 cents per kw/hr
These rate increases are not retroactive. If you go over the baseline, the first 100% of baseline will be charged at the lower rate, while the amount used above the baseline will be at the second tier rate. If you are using over 200% of your baseline, you will be charged four different rates for different portions of your electric consumptions, all on one bill.
The rates used in the above example are for Northern California from the Central Valley north to the border with Oregon and may not be accurate by the time your read this.
Time of Use Rates
PG&E also offers rates that take into consideration the time of day the electricity is consumed. These programs change from time to time but currently the program PG&E offers is called the E7. Time of use rates offer a discount for non peak use but charge a bundle for use during peak hours. These plans are designed for those who are at work in the afternoon and early evening so they don’t work for everyone. If you can have your grow lights off during the peak hours this program could save you some money. If you decide to switch to a time of use program, be aware you may be required to stay with this rate program for at least one year.
The peak hours for this program are from 12:00 pm through 6:00 pm or 1:00 pm through 7:00 pm depending on the time of year.
The following PG&E rates are for E7 “time of use” program for Northern California
Tier 1 – Up to 100% of Baseline
Off Peak – 7.5 cents per kw/hr
Peak – 29 cents per kw/hr
Tier 2 – 101% to 130% of Baseline
Off Peak – 9.2 cents per kw/hr
Peak – 31.5 cents per kw/hr
Tier 3 – 131% to 200% of Baseline
Off Peak – 24.6 cents per kw/hr
Peak – 46.9 cents per kw/hr
Tier 4 – 201% to 300% of Baseline
Off Peak – 28.6 cents per kw/hr
Peak – 50.9 cents per kw/hr
Tier 5 – 300% + of Baseline
Off Peak – 28.6 cents per kw/hr
Peak – 50.9 cents per kw/hr
As you can see, the off peak rates are considerably discounted, but you will pay a premium for electrical use during peak periods. If you can time your lights correctly, you could definitely save some money with this program.
PG&E’s Care Program
Most if not all utility companies offer discounted usage rates for low income families who meet specific qualifications. PG&E’s low income program is called CARE and is available to those on public assistance programs and to residences with yearly household incomes totalling under $31800. If you qualify for this program your usage rates are significantly reduced and the over baseline use rate is minimal.
Tier 1 – Up to 100% of Baseline – 8.316 cents per kw/hr
Tier 2 – 101% to 130% – 9.563 cents per kw/hr
Tier 3 – 131% to 200% – 12.471 cents per kw/hr
Tier 4 – 201% to 300% – 12.471 cents per kw/hr
Tier 5 – 300% + – 12.471 cents per kw/hr
As you can see, the CARE programs 300% of baseline rate 12.4 cents per kw/hr is only .2 cent more per kw/hr then the standard rate for under baseline usage. Not every household will qualify for this program, but home inspections are not required and proof of income is only asked for on some occasions. If you are running several 1000 watt lights, this program can literally cut your power bill by almost 65%.
Commercial electric rates are meant for businesses so there is no baseline and the rate per kw/hr is the same no matter how much you use. For commercial rate plans using under 4000 kw/hrs per month the rate is generally a bit more then the residential “below baseline” rate, but for those running a few lights should average out to savings.
The following commercial rates are based on a three phase (240 Volt) In Northern California PG&E calls this the A1 rate plan which is ideal for those using up to 4000 kw/hrs per month.
44.4 cents per day +
Summer 19.712 Cents per kw/hr
Winter 14.747 Cents per kw/hr
The standard A1 program is ideal for grow rooms running up to 10 lights on 12 hour cycles. If you are using more power then this, one of the other programs will probably save you money.
There are also commercial plans that use adjustable rates based on; off peak, partial peak, and peak periods. This is a bit complicated to explain so please refer to PG&E’s commercial rate chart.
Obviously, if your grow room can draw it’s power from a commercial electric account you could potentially save a ton of money each month. It is also a lot less suspicious for a business to consume large amounts of power, so the utility company is unlikely to report you.
You can’t simply switch from a residential account to a commercial account just because, but you may be able to switch if you run a power intensive business from your garage or outbuilding. Be sure to check your zoning regulations to make sure having a business on your property is permitted. Expect that the utility company is going to ask for your business license and to see the equipment drawing the power before they agree to a commercial rate. If you are going to invite the utility company to inspect your “business”, make sure you do this before you set up your grow room. You might also want to inquire with the local fire department and see if annual inspections of your new business are required.
If you can’t change your residential service over to a commercial account, you might want to consider adding a second meter. While the setup will cost some money in the short run, over time this is going to add up to huge savings.