Upcoming electric bill

So Masterjoe here again with a 4.5 KW solar system. Checking the production of the system through the latter part of October into November I notice on the best day the system produced 10.7kw that seems awfully low. According to PVwatss site I should be in the neighborhood of 16kw accounting for a modest 14% system loss this time of year in our area. With consumption at roughly say 40-50kw per day we are seriously outconsuming what the pv system is producing. I have 4 kids I chase after to keep the lights and AC off. Consequently since this is a battery backup we are not running off the battery bank at night. So from what i can gather, I have spent thousands of dollars to save maybe $20 on my energy bill. Also in the event the utility goes down and the panels don't produce even if they do I doubt I would have enough battery backup to last me 12 hours. Am I missing something here, because I really don't get it? I know the usage is bad but I expected the system would produce more than it is. I read so many stories about people with an electric bill near zero. Is this really fathomable? The way it is now we produce 200-500 watts more for 4 hours a day. The rest of the time we are pulling from the grid. From Oct 14 - Oct 31 we produced 137.2kw and Nov 1 - Nov 6 36.7kw. The inverter is running its charge cycle early in the mornings from the grid as well. I appreciate the patient explanation on a wondering mind, be gentle lol.
4.5kw 24v System
18 Solartec 250w polycrystalline panels
Xantrex XW4024 Inverter/Charger
Conext MPPT 80-600 Charge Controller
12 Trojan L16G-AC 20 hour 390ah batteries tied in 3 strings at 1170ah total
18 Solartec 250w polycrystalline panels
Xantrex XW4024 Inverter/Charger
Conext MPPT 80-600 Charge Controller
12 Trojan L16G-AC 20 hour 390ah batteries tied in 3 strings at 1170ah total
Comments
Depending on how your system is set up, you may only be seeing the extra energy created over what you are using. So your 'extra' wattage may be hidden in your usage that wasn't drawn from the grid.
I have no idea, where you are located, but this time of year is the worse for much of the country. Between short days and slow moving fronts that make areas cloudy for days for days on end. About 3 years a go in Central Missouri, we had 13 days with just a single hour of direct sunlight!
I PVwatts uses an average solar insolation over many years. This time of year things can vary hugely! The return will be slow and steady, you are in the worse time of year for return on your investment.
- Assorted other systems, pieces and to many panels in the closet to not do more projects.
http://solarelectricityhandbook.com/solar-irradiance.html
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
Since you are probably load shaving, (I don't think the SW will sell to the grid) and not cycling your batteries to any depth, then PV production will be limited to the amount of power the loads consume during the time of production. This should vary with the weather and battery SOC. It could be a good bit less than the PVwatts estimate. Also, I would think that your system would work like a normal off grid system if you lost the grid. By the way, I have a similar backup system, but a bit smaller array, however I cycle my batteries fairly deeply and I average about 10 kWhs per day.
Rick
Second system 1890W 3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.
5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
Thanks for the correction, I wasn't aware that Xantrex made a 4000 watt XW series inverter. I guess lower production is due to reduced solar hours, but you would think that PVwatts would reflect that.
Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
kW is an instantaneous reading.
What was your consumption , in kWhr, before you installed your system? What has it been since? compare the same months in different years is useful as opposed to 'over the summer' etc.
hth
KID #51B 4s 140W to 24V 900Ah C&D AGM
CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM
Cotek ST1500W 24V Inverter,OmniCharge 3024,
2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
West Chilcotin, BC, Canada