LFP backed whole house solar

[John in Santa Cruz]

Its come down to the point where you could build a very practical 20 KWH battery, install sufficient rooftop solar, that you could take your house off the grid much of the year.

with the new LFP 'rack' batteries coming out, doing a 48V system with 4 x 5 KWH batteries is totally doable for $10,000 or less, and a few $100 in racking and wiring. Top of the line Victron true sine inverters are $1000 per 3KW and can be ganged. I'm pretty sure I could run my whole house off one of those.

I dunno the current costs for rooftop solar panels, but lets call it $400/400W for raw panels, cuz I think thats close now for good LG class A panels.... a random calculator site suggested I want 10KW of raw panels at my zip for my estimated daily load, so thats like $10K more. so $20K for batteries plus solar panels, add about $5000 more for the inverter and charge controllers and stuff and we could be nearly independent of the grid.

[JeffreyG]

My electric bill was $1328 in 2021. So I'd be looking at about a 19 year break even, ignoring the time value of money. There is also the significant cost of installation.



It's getting there, I guess, but still a way to go in terms of cost.

[Upfisk]

We are fully off grid in AZ and have been for 13 years. We have 2500 watts of solar panels collecting sun. They are only 120 watts each showing how old this system is. Today panels are sized to 400 watts or more. We use an inverter charger 4860 by now Schneider. This runs our 48 volt system and is 6 kw. We have 24-2 Volt AGM batteries rated at 1400 amps each, they weigh 160 pounds each. At peak sun we are collecting 1200 watts, we do have mini split A.C. that we can run for 6 hours a day. Our best collection day was 12 KW, more normal collection is 10 kw. We installed and wired everything ourselves. Total cost was $20,000 15 years ago. Our first set of batteries was L16 6-volts, they died after 5 years. We have been running these AGMs for 8 years. They are showing no sign of deterioration yet. Shelving was insignificant at about $200. Inverter charger was about $5000, same with the solar panels. The battery total for both sets has been about $10,000. Batteries are by far the most expensive part of the system as nothing else wears out. While we were building this house we also lived off grid in a 28 ft travel trailer, with a single 120 watt panel and 2-6Volt batteries. We spent summers building the house, then winters on our sailboat (also off grid). We are 3 miles from the nearest power pole and Arizona Public Service has no plans to ever install power to our area. We also have a 10 kw diesel generator that we ran only when our 1st set of batteries was dying. It was used during construction to run power tools, but since the house was up and running it just sits.

[Chamberman]

Its not worthwhile for many people out there. Unless your end goal is only to be independent of the grid, irregardless of costs, then most folks are far better off investing in simple efficiency improvements to their house. By simple I'm not necessarily talking about going out and buying an expensive 20 SEER AC to replace your old 12 SEER unit or turning your thermostat to uncomfortable levels. I'm talking about boosting insulation levels where possible and fixing air leaks in the ductwork of attic based AC systems. The average older house out there will many times have air leaks in the attic and wall plenums that exceed 10% of system air flow. Also purchasing a Kill a Watt or similar power meter to find large ghost loads or extremely inefficient appliances in the house that can be eliminated.

Back in 2005 I started a side business doing home energy efficiency ratings. I went through a Energy Star training class and received a certification to rate homes. I had all of the equipment for testing the building shell and ductwork, ie. Blower door, Duct Blaster, etc. After about a year of doing this work I grew tired of working full-time in the semiconductor industry and then spending my off days slugging around in peoples hot attics and gave up the notion of that business.

My house was fairly new back then, built in 2001, but even then it benefited greatly from simple upgrades. My peak monthly usage in the summers was exceeding 3000kwh with some peaks hitting 3300kwh/month. After many sealing improvements and some insulation improvements my house usage dropped well below 3000kwh peak in the summer. In fact the 5 ton/12 SEER AC unit that was originally installed became far too much capacity and was short cycling on my 2500 sq/ft home. In 2008 I installed a 4 ton/13 SEER system, not a super high end system by any means, and my energy usage dropped to a peak of 2100kwh in the summer all with the same thermostat settings as my earlier high usage periods. In total my yearly energy usage dropped by >5000kwh total due to all of the changes I had made. So at .10/kwh I'm saving in excess of $500/yr. Now after all these years my upgrades are well paid for and its like getting a tax free $50 bill in my pocket every month.

[splitting_lanes]

Here in California where both John and myself live, there will be some rate changes for electricity and grid connected solar.

It may make sense to disconnect from the grid to avoid the monthly connection fees. We’ll see.

PG&E’s original proposal was to charge almost $100 per connection if you have solar. That’s not going to fly, but there will be some sort of mandatory charge for simply being connected to the grid. So people like me that have solar will be investigating ways to get off the grid.

[Iowa Dave]

Observations on energy efficiency vary somewhat depending upon the construction of the dwelling, regional location, landscaping, and local utility costs.
Where we live, there’s a Home Owners Association. Our annual dues pay for three main items. Water well electric and maintenance, entrance road snow plowing and entry road maintenance. This means we do not have a monthly water bill and use all we want. Some folks have pools, I water my garden and our trees.

Our main energy improvements have been as follows: The installation of a geothermal heating and cooling system, The change out of original windows and doors, A 7.6 kWh solar array that provides excess electricity for us including running the geothermal. We have a metal roof rated for baseball sized hail and 125 mph winds. It withstood without any damage the derecho wind in 2020 of 142 mph for 45 minutes. Our home is constructed of 6”X8” Western Red Cedar Logs. The thermal mass is significant and replaces conventional insulation. When I stain the logs I thoroughly re-caulk wherever needed. I use a Milwaukee 12 volt caulk gun and I am a caulking fool. It makes a difference. We’ve done about what we can to achieve energy independence and lower monthly bills. We use about 350 gallons of propane a year to enjoy the fireplace, supplementally heat the hot water, and cook on the gas stove.

Our electric bill for transmission service is about $13 a month. Payback on the solar is 5 years in the future yet. So if I die before that I will be pissed off, but till then we’re happy, still planting trees for the future and studying electric vehicles.

Who knows what the future holds? Everything costs money, where you decide to spend yours is fortunately your choice.
As my old friend “Boge Johnson” who was the flag man at the world famous Marion County Speedway in Knoxville Iowa used to say. “It costs money to go racin”.
Have a great day and be good to yourself. We’re waitin on the next snow and going to watch some football today.
Iowa Dave

[Brian B-P]

Originally Posted by Upfisk

We have 24-2 Volt AGM batteries rated at 1400 amps each, they weigh 160 pounds each.

I assume that was supposed to be 1400 amp-hours of charge (not amps of current) per battery.

That's about 57 kWh of energy storage nominally, but you wouldn't use all of it.

Originally Posted by Upfisk

At peak sun we are collecting 1200 watts, we do have mini split A.C. that we can run for 6 hours a day. Our best collection day was 12 KW, more normal collection is 10 kw.

I assume that would be a best collection day of 12 kWh (of energy), and normal day of 10 kWh (of energy), not kW (of power).

[cpaharley2008]

Originally Posted by Iowa Dave

Observations on energy efficiency vary somewhat depending upon the construction of the dwelling, regional location, landscaping, and local utility costs.
Where we live, there’s a Home Owners Association. Our annual dues pay for three main items. Water well electric and maintenance, entrance road snow plowing and entry road maintenance. This means we do not have a monthly water bill and use all we want. Some folks have pools, I water my garden and our trees.

Our main energy improvements have been as follows: The installation of a geothermal heating and cooling system, The change out of original windows and doors, A 7.6 kWh solar array that provides excess electricity for us including running the geothermal. We have a metal roof rated for baseball sized hail and 125 mph winds. It withstood without any damage the derecho wind in 2020 of 142 mph for 45 minutes. Our home is constructed of 6”X8” Western Red Cedar Logs. The thermal mass is significant and replaces conventional insulation. When I stain the logs I thoroughly re-caulk wherever needed. I use a Milwaukee 12 volt caulk gun and I am a caulking fool. It makes a difference. We’ve done about what we can to achieve energy independence and lower monthly bills. We use about 350 gallons of propane a year to enjoy the fireplace, supplementally heat the hot water, and cook on the gas stove.

Our electric bill for transmission service is about $13 a month. Payback on the solar is 5 years in the future yet. So if I die before that I will be pissed off, but till then we’re happy, still planting trees for the future and studying electric vehicles.

Who knows what the future holds? Everything costs money, where you decide to spend yours is fortunately your choice.
As my old friend “Boge Johnson” who was the flag man at the world famous Marion County Speedway in Knoxville Iowa used to say. “It costs money to go racin”.
Have a great day and be good to yourself. We’re waitin on the next snow and going to watch some football today.
Iowa Dave

Hope to see you in Osoyoos in May, Dave.....and Rita also, as well as Jake..... stay warm til then.

[Upfisk]

That's about 57 kWh of energy storage nominally, but you wouldn't use all of it.


Yes, we do store about 60kw of power. We sized the system for 7 days of cloudy weather. We have had 3-4 days of poor charging and the battery bank is holding up fine. I don't think we have ever been below 50% charge.

[Mike Lewis]

My only experience with solar power is with my trailer. I have traveled for weeks on end using just the power produced by the trailer's solar panels. I have been impressed by how variable and unpredictable solar power generation is, something I didn't foresee.

My electric bill at home for 2021 was just over $2,000, and I use a heat pump for heating/cooling. As long as electricity prices remain reasonable I won't consider solar power for my home.

Some of my ham radio friends have solar panel arrays for their homes, but I don't think they are disconnected from the electric grid.

[Mike G]

Originally Posted by Iowa Dave

Our electric bill for transmission service is about $13 a month. Payback on the solar is 5 years in the future yet. So if I die before that I will be pissed off...
Iowa Dave

If you die before that, won't you have more important things to think about than solar payback?


Our electric bill is less than $900/year. And we have big trees shading the roof. So, even though I like solar, it's not in the cards for us.

[Iowa Dave]

Originally Posted by Mike G

If you die before that, won't you have more important things to think about than solar payback?


Our electric bill is less than $900/year. And we have big trees shading the roof. So, even though I like solar, it's not in the cards for us.

Our electric bill was about twice what yours is or better. (2200 in 2020) Our house is not shaded. When we lost several big trees on the south lot line that borders a farm field in the derecho, we knew the solar install down there would work out well. The 26% federal tax credit didn’t hurt either.

I don’t mind saying stupid things as long as I don’t offend somebody. So comments about death before I regain my investment are standard with me. When I bought a new outboard motor in 1988 I bought two gallons of mixing oil at the same time. My brother in law observed “Ahh, a lifetime supply” because he’d seen me buy “too much” in the past. That’s when I started saying “if I die before ……. And actually get satisfaction out of throwing out empty boxes, bottles and jugs, except if they contained liquor.
Iowa Dave

[brroberts]

I live in the country, and tow, so as of yet a BEV won’t work for me. Electricity is about $900 per year and about 300 gallons of propane for the house. We have a small pole barn house. Nothing is terribly energy efficient.

There’s a lot of sun and wind here, but as of yet, personal solar and wind don’t pay off. I think eventually they will, but by then I’ll probably be too old for payback in my lifetime. I do hope eventually we can reduce our use of fuels that take millions of years to renew. The barn, when the interior is done, will be all mini splits.

I’ve looked at hybrid cars, but as of yet, I can’t make the numbers work for our driving either.

I’m glad some are willing to take the cost of energy options even when it doesn’t pay because it helps move the technology forward for the rest of us.

[gbaglo]

I would insulate the attic better, but by the time I was done, the house would be demolished. Same with replacing single pane windows. I have a small cracked pane that I fixed with hot glue 35 years ago.

I take consolation in that there is good exchange of air in this house.

[outwiththedogs]

We moved to Denver in 2014 and I finally got to really investigate solar. At the time the federal tax rebate was a little over 30% if I recollect and that helped a lot. Because of our roofline and neighbor’s trees we ended up putting all the panels on our garage roof. It’s completely covered but I don’t mind the look of roof panels, the garage was just the best site. We pay around $10/month for ‘line charges’ to Xcel and have always gotten a monthly rebate check ranging from $3 to $15 depending on time of year and the seasonal sun exposure. Meanwhile, Xcel has raised their rates enormously this last year. I’m enough of an old hippie that I love using the sun power.

If I had my druthers I would copy Iowa Dave’s geothermal system. One of our neighbors has, and loves, hers. However this 90 year old bungalow is not easily retrofitted. We do what we can with our solar, rain barrels, a xeric native plant garden, etc. It satisfies something for us to make our footprint just a little smaller. Besides, it’s fun and keeps me entertained. And yes, we do realize that having a trailer and traveling is a sizable footprint. Call us Sasquatches.

[Mike Lewis]

For those considering a solar powered home I suggest that you not put the panels on the roof. Solar panels require periodic cleaning, and roof-mounted panels aren't easily accessible.

[Vermilye]

Originally Posted by Mike Lewis

For those considering a solar powered home I suggest that you not put the panels on the roof. Solar panels require periodic cleaning, and roof-mounted panels aren't easily accessible.

And, as a good friend discovered, when you need a new roof after installing panels, it gets expensive!

[Brian B-P]

Originally Posted by Vermilye

And, as a good friend discovered, when you need a new roof after installing panels, it gets expensive!

It would be rational to use long-lived roofing (metal?), and to install new roofing material as the first stage of the solar array installation.

[Brian B-P]

Originally Posted by Mike Lewis

For those considering a solar powered home I suggest that you not put the panels on the roof. Solar panels require periodic cleaning, and roof-mounted panels aren't easily accessible.

For most homes, that would mean not installing solar panels, since there is no other good place for them.

[splitting_lanes]

Originally Posted by Mike Lewis

For those considering a solar powered home I suggest that you not put the panels on the roof. Solar panels require periodic cleaning, and roof-mounted panels aren't easily accessible.

My panels have been on the roof for ten years and the only cleaning they’ve ever had was from rain. The power just doesn’t drop enough to justify the water usage when we are nearly always in drought conditions.

I did the roof, then had the panels installed.