Mini off-grid setup and configuration for a 500w draw inquiries

[Sunking]

If I invest in two 125 AH 12 VDC batteries for about $500 and it will give me at least 3-years of daily full charge and discharge usage, then is it a worthwhile investment to capture that energy for later use?

Here is the breakdown. Those batteries will afford you the luxury of about 1 Kwh/day of use. At $500 for 3 years will allow you to use 1095 Kwh. That means electricity just for the batteries is $0.47/Kwh or about 300 to 500% more than what you pay the electric company. What a deal huh?

FWIW based on what you stated at 400 watts demand, allows you about 2 hours per day run time with that high of discharge rate for such small batteries.

[SunEagle]

Will have to scrap this solar plan. The initial & on-going maint. costs are just way too much for so little return on investment. My cost here in Southern CA is 29 cents/kwh. It jumps up to 36 cents/kWh during peak summer months (June-Aug). But overall pretty reasonable rate. That's way under $5/kWh. Just a waste to see all of the sunlight not being utilized though. Perhaps another decade or two solar tech will be more realistic?

Well you should scrap the battery part of the plan. You can still go with solar panels with a grid tie system that will pay for itself in Southern CA.

The cost for an energy storage system like batteries is very expensive and should only be looked at if you can't connect to the grid or you are not allowed to run a generator all hours of the day.

[Sam Lee]

Here is the breakdown. Those batteries will afford you the luxury of about 1 Kwh/day of use. At $500 for 3 years will allow you to use 1095 Kwh. That means electricity just for the batteries is $0.47/Kwh or about 300 to 500% more than what you pay the electric company. What a deal huh?

FWIW based on what you stated at 400 watts demand, allows you about 2 hours per day run time with that high of discharge rate for such small batteries.

With your calculations, this is not a huge saving. 2 hrs per day will not work for me. I'm paying roughly $0.29/kWh. For summer months, only about $0.37 max. No wonder why solar is not widely deployed in my area. I'll take your advice and not pursue this project any further. Will do more power intensive workstations at work and use the latest and fastest laptop at home. This whole solar thing is great as a fun hobby to learn more about solar panel & batteries, but just not practical unless I spend more than $15K to get a Grid Tie system as Naptown suggested.

[FloridaSun]

With your calculations, this is not a huge saving. 2 hrs per day will not work for me. I'm paying roughly $0.29/kWh. For summer months, only about $0.37 max. No wonder why solar is not widely deployed in my area. I'll take your advice and not pursue this project any further. Will do more power intensive workstations at work and use the latest and fastest laptop at home. This whole solar thing is great as a fun hobby to learn more about solar panel & batteries, but just not practical unless I spend more than $15K to get a Grid Tie system as Naptown suggested.

No, not practical for saving money but if you do have $1500+- to play with for your daily 400-500 watts it is a fun hobby and can be very educational. Not sure your age or kid's but could be a great way do a joint project, keep minds busy on future technology. If you're younger, without older kids, you can learn the basics and more to develop a good grid tie system later on. There's a lot to learn and you've just processed the first lesson, energy is not free, stable grid free independence costs even more.
Get a Kill-a Watt meter and see just how much juice you're using thruout the house. Be aware of what it costs to leave items running while you're away for a few hours. It all adds up. You may be able to decrease your monthly grid bill enough to have some extra cash, justify playing more with solar.

[Sam Lee]

No, not practical for saving money but if you do have $1500+- to play with for your daily 400-500 watts it is a fun hobby and can be very educational. Not sure your age or kid's but could be a great way do a joint project, keep minds busy on future technology. If you're younger, without older kids, you can learn the basics and more to develop a good grid tie system later on. There's a lot to learn and you've just processed the first lesson, energy is not free, stable grid free independence costs even more.
Get a Kill-a Watt meter and see just how much juice you're using thruout the house. Be aware of what it costs to leave items running while you're away for a few hours. It all adds up. You may be able to decrease your monthly grid bill enough to have some extra cash, justify playing more with solar.

While in the same planning state of mind, I'm curious to know how many 250-w 24vdc panels are needed to power 400-watt of AC power on a full hot sunny day from 10-5 pm? Battery will kick in when sunlight is not at full intensity.

I will have a 24 vdc DC-AC 1000w inverter with rated 85% efficiency. It gets complicated as the biggest charge controller I can find is 30A. Have to look at how much current the deep cycle battery can handle. Probably under 30A. But curious to know how many 250-w panels needed to achieve a 400 W of 120 VAC power without relying on battery. I'll be using battery on a reserve basis. But would prefer not to on a full sunny day.

So far I'm looking that the panels have to be wired in parallel. W=VxA. 400=120x3.3. But don't know how to figure when there's DC involved.

I bought the Kill-A-Watt meter a while back. Surprises: A Verizon FIOS set top box will always consume 15 w regardless if you turn it on or not. It's probably doing some background spying. So I typically pull the plug off completely when not in use for several days. A typical SATA-3 3 Tb hdd will consume 9 w in standby. 11 w in operation mode. In a RAID array of 8, it adds up to almost 100 w just for that rack tower. As cheap as it sounds, I saved about $15/month just unplugging these devices after some serious measurements made. $15/month doesn't sound much. But it adds up year after year.

[Naptown]

Stop with the battery thing It makes no economic sense if you are already connected to the grid and just want to reduce the electric bill.
You are using 400W for 12 hours a day or 4800 watt hours a day. If you do grid tie it will take about 4 250W panels to produce that average amount of electricity each year
If you start connecting batteries it will take 6 if you use a MPPT controller and 8 if you use a PWM and it will take at least 2
4800 Watt hours a day is HUGE for a battery system
You should start with a 4 panel Enphase system grid tie and expand from there if necessary.

[Sam Lee]

Stop with the battery thing It makes no economic sense if you are already connected to the grid and just want to reduce the electric bill.
You are using 400W for 12 hours a day or 4800 watt hours a day. If you do grid tie it will take about 4 250W panels to produce that average amount of electricity each year
If you start connecting batteries it will take 6 if you use a MPPT controller and 8 if you use a PWM and it will take at least 2
4800 Watt hours a day is HUGE for a battery system
You should start with a 4 panel Enphase system grid tie and expand from there if necessary.

Ah yes. Within $3-4K is reasonable for my budget. Good thing that I don't rush into buying anything unless thorough research on the current solar panel market is made. If I did, I'd be wasting several grands on a DIY starter system before getting the right one. Still researching..

[FloridaSun]

While in the same planning state of mind, I'm curious to know how many 250-w 24vdc panels are needed to power 400-watt of AC power on a full hot sunny day from 10-5 pm? Battery will kick in when sunlight is not at full intensity.

I will have a 24 vdc DC-AC 1000w inverter with rated 85% efficiency. It gets complicated as the biggest charge controller I can find is 30A. Have to look at how much current the deep cycle battery can handle. Probably under 30A. But curious to know how many 250-w panels needed to achieve a 400 W of 120 VAC power without relying on battery. I'll be using battery on a reserve basis. But would prefer not to on a full sunny day.

So far I'm looking that the panels have to be wired in parallel. W=VxA. 400=120x3.3. But don't know how to figure when there's DC involved.

I bought the Kill-A-Watt meter a while back. Surprises: A Verizon FIOS set top box will always consume 15 w regardless if you turn it on or not. It's probably doing some background spying. So I typically pull the plug off completely when not in use for several days. A typical SATA-3 3 Tb hdd will consume 9 w in standby. 11 w in operation mode. In a RAID array of 8, it adds up to almost 100 w just for that rack tower. As cheap as it sounds, I saved about $15/month just unplugging these devices after some serious measurements made. $15/month doesn't sound much. But it adds up year after year.

Time for you to visit the 'off grid electric systems' forum on this site, read all the stickies at least to get more familiar with how all the parts of a well designed system work. Everything will become clear..... after reading it over and over like I had to do when first starting.

[Sam Lee]

Time for you to visit the 'off grid electric systems' forum on this site, read all the stickies at least to get more familiar with how all the parts of a well designed system work. Everything will become clear..... after reading it over and over like I had to do when first starting.

Ah yes. Thanks for the tip. This section is filled w/ valuable information. Gonna take many weeks to really know this stuff. After the deep research & study, may have a different outlook to solar power in general.