OT: Time Shifting My Electrical Usage

jpf321

Most of you may have noticed I've been quiet for the last few weeks. Mainly because I was prepping for Summer by Time Shifting some of my electrical usage.



Being a NYC ConEd customer, I signed up for their TOU (Time of Use) Billing program. During Peak hours (M-F 10a-10p PEAK) they charge me, all in, $0.23/kWh .. ALL other times (and some Holidays), they charge me $0.08/kWh. Being that I had a supply of batteries collecting dust from a previous project, I set out to run some of my "Always On" load on batteries during PEAK and recharge the batts during OFF-PEAK.



Prior to getting the system set-up I was pretty consistently having 60% OFF-PEAK usage .. with my new setup I now have a 79% OFF-PEAK usage. So for the month, I will likely still have the same TOTAL kWh consumption, but I have shifted more of it to the OFF-PEAK time where it is ~66% cheaper.



I have been able to time-shift my Computers, AV Equipment, Misc Chargers, LCD TV, Cable Box, Routers, PlayStation, etc. There are things that I won't necessarily be able to time shift cost effectively.. refrigerators, George Foreman Grill, Microwave, Air Conditioners, Dishwasher/Washer/Dryer (we try to run only OFF-P) and other high-load units. But I fairly consistently have been able to move 5-6kWh/day over to my batteries.



I've attached a simple sketch of my set-up .. if anyone has any questions or wants more details, drop me a line. My first full billing cycle hasn't run yet so I don't have any exact $$ figures to share, but when I do I'll post them here .. my month ends on the 25th. I think ConEd is really going to scratch their head when they get their next reading.



If I were to do it again, I'd set it up as a 24V system to lower the amperage on the DC side.

Kevin_in_Denver_2

Non-TOU Rate?

What price do they charge for a flat rate?

Do you have a demand charge?

jpf321

non-tou

My aunt found a Nov 2010 bill that listed supply as $0.09 and delivery also $0.09/kWh. So about $0.18/kWh. I seem to remember it being around there. When I check the ConEd website it's kind enough to show me that 1/24/11-2/25/11 the supply was $0.08/kWh .. but they don't show the delivery. I believe that all rates are bumped up in the summer.



I believe that Demand Billing is limited to Commercial/Industrial properties here. I am EL1 Residential Zone J. If you are truly interested, I think there maybe more about demand billing rates here: http://www.coned.com/rates/supply_charges.asp

haaljo

Electric Companies can be a little sneaky

Are they charging extra for the TOU meter? Used to.

Will you be including inverter losses in your saving calculations?

The good news is you are now in their database for future demand response opportunities. Like additional savings if you are willing to let them control AC load.

At 8 cents/kWh, you could even put an electric coil in your steamer. During off peak hours make steam with electricity. $4 oil for 130,000 BTU's vs $.08 electricity for 3,400 BTU's. And electricity i s "100 percent efficient" :-)

jpf321

beating em at their own game ...

I like to think that I'm actually beating them at their own game by exploiting them at night.



There is no extra monthly/yearly charge, nor install charge for going TOU. The only rules were: .. you can go on for free and come off at ANYTIME for free .. but if you come off, you are not allowed back on for 18months.



Of course, the "ElectricCo" meter swapper man broke part of my meter plan when he did the meter swap ... completely denying the fact of course .. and then *I* needed to repair the broken part as "filed work" .. apparently the meter pan is "customer equipment", and ConEd obvously had a record of the required repair since they broke it ... I got that sorted out in short order and raised bloody hell with the TOU people since the repair costs significantly outweighed any potential short-term savings I would be realizing by going TOU .. but so it goes....

Polycarp

battery losses too

Not just inverter losses, but battery losses too.  Lead-acid batteries have a charge efficiency profile that varies depending on how much of a charge the battery has.  So, at lower charge levels, charge efficiency can be very high, but at higher charge levels, charge efficiency drops precipitously.  A frequently-used rule of thumb is 80% aggregated charging efficiency. 



This rate differential certainly seems to be large enough to more than cover the efficiency losses, but it would not take a whole lot of charging at the "top" of the battery capacity to obliterate that differential.

jpf321

quick update....

after 1 full billing cycle (meter was read today) .. here are 2 charts and some data to show what effect my time-shifting had.



please note that the $ figures in the data are based on the straight per/kwh costs for SUPPLY and DELIVERY .. they do not reflect the total bill that includes other taxes and basic service and such.