Another Solar Thread

Clem72

Well-Known Member
Depending on the size of the system, yes, it can be.

The emergency backup electric coils are 12kW (give or take). If it runs 12 hours/day in emergency mode, and using 10 cents/kWH, that's $438.30 per month just for the heat.

Guess I just don't know if 12 hours a day (50% runtime) would be normal? And is this only when it's below freezing outside? I remember I was looking at a low-ambient temperature unit a few years ago that said it would work to 0 degrees, but I think that was in combination with electric heat (but not 100% resistive heating).

I'm interested because I have been considering moving away from town, but there is no way I could afford to treble my energy bill.
 

Chris0nllyn

Well-Known Member
Guess I just don't know if 12 hours a day (50% runtime) would be normal? And is this only when it's below freezing outside? I remember I was looking at a low-ambient temperature unit a few years ago that said it would work to 0 degrees, but I think that was in combination with electric heat (but not 100% resistive heating).

I'm interested because I have been considering moving away from town, but there is no way I could afford to treble my energy bill.

It can be normal if it's really cold.

Normally the heat pump runs, but HPs are not efficient below a certain temperature (usually about 40*) and the emergency heat kicks on (or manually turned on via the t-stat) when the heat pump can't gather any more heat from outside air.

Now, electric emergency heat isn't mandatory. You can get a hybrid system which is a heat pump with oil or propane backup heat. Most of the new systems are already setup for it and a simple outdoor thermostat/sensor is installed to let the system know when to switch over to oil/propane heat when the temp is too low for efficient heat pump use.

This is not to be confused with auxiliary heat. It's the same coil, but helps defrost the condensor coils. There's no getting around that, but still costs $$$ when it's on.
 

Gilligan

#*! boat!
PREMO Member
Depending on the size of the system, yes, it can be.

The emergency backup electric coils are 12kW (give or take). If it runs 12 hours/day in emergency mode, and using 10 cents/kWH, that's $438.30 per month just for the heat.

That's the one thing that's got me worried about what we went with in our new still-under-construction house. 23 SEER units running a 5-zone system, but no backup for the heat except the electric coils. Super tight and super insulated...but still concerned. This will be the first house I've owned that had no fuel-based backup heat.
 

Chris0nllyn

Well-Known Member
That's the one thing that's got me worried about what we went with in our new still-under-construction house. 23 SEER units running a 5-zone system, but no backup for the heat except the electric coils. Super tight and super insulated...but still concerned. This will be the first house I've owned that had no fuel-based backup heat.

What ton system?

J calcs (heat loss) should be low if built tight. I've seen some coils on larger systems as big as 24kW. I'd be using sleeping bags.
 

black dog

Free America
My electric bill last month was $55 and I don't have solar.

Yep mine was half of that, my NG made up the difference.
My sailboat has panels and a wind turbine, lots of time to keep everything happy happy when it all gets used and not in a slip.

It's easy to have a break even on a month that you don't need heat or AC.
I'd like to see how well it does on cost this coming Aug and Dec.
 

Clem72

Well-Known Member
Answers in italics above.

Anyone look into the Tesla solar tiles? They look like regular shingles and have a lifetime warranty. I assume they dont come cheap.

https://www.greentechmedia.com/articles/read/heres-how-much-a-tesla-solar-roof-will-cost-you

Looks like the installed cost is between asphalt shingles and tile. If you consider the value of the energy production, they may be cheaper than asphalt. I didn't see any mention of cost for inverters for grid tie, which isn't cheap.
 

Chris0nllyn

Well-Known Member
https://www.greentechmedia.com/articles/read/heres-how-much-a-tesla-solar-roof-will-cost-you

Looks like the installed cost is between asphalt shingles and tile. If you consider the value of the energy production, they may be cheaper than asphalt. I didn't see any mention of cost for inverters for grid tie, which isn't cheap.

Keep in mind, that cost is assuming only 35% of the tiles are solar tiles. Not the whole roof. It also doesn't facotr in any incentives, which would bring the cost down a bit.

Consumer reports did the math and found that a 3,000sq. ft. solar roof would cost $73,500 compared to a asphalt roof at $20,000. Plus a ton of assumptions,
So how could a $73,500 roof be considered cost-competitive with a $20,000 asphalt roof? To compensate for the proposed added value of the “free” electricity from Tesla’s roof, we added in $2,000 a year, over the lifespan of the roof. That’s a typical electric bill in states where solar is big, like California, Texas, and North Carolina.

Tesla says the life expectancy of its tiles will be 30 years. So that adds $60,000 to the value of the roof. (Our rough estimate assumes our hypothetical Solar Roof homes generate exactly as much electricity as they use.)
http://www.consumerreports.org/roofing/heres-how-much-teslas-new-solar-roof-shingles-could-cost/

Add in one or more Powerwalls (battery/inverter combo by Tesla) at $6,500 each and it's not as cheap as they make it seem. They factor in electricity savings, which is a good thing to consider, but Joe Blow with a house in almost complete shade (like mine) won't generate that much electrcity.

Add in additional labor costs (because, as the article points out "roofers aren't electricians") and that's an expensive roof front loaded with 30 years of electrical costs.
 

Clem72

Well-Known Member
It's definitely not for everyone. I certainly wouldn't take the battery upsell.

That CR report is from BEFORE Tesla released any pricing information, and that figure they give is what they ESTIMTE it would have to be to be competitive. The article I listed references ACTUAL pricing, which appears to be much less than the CR estimates.

And the installation costs includes their "certified" installers. You buy their product, they install it.

So while it's probably not the best idea for SoMD, if you live in Sunny SoCal where tile roofing is prevalent and shade trees overhanging your roof are not, this is looking to be an affordable alternative.
 

Chris0nllyn

Well-Known Member
It's definitely not for everyone. I certainly wouldn't take the battery upsell.

That CR report is from BEFORE Tesla released any pricing information, and that figure they give is what they ESTIMTE it would have to be to be competitive. The article I listed references ACTUAL pricing, which appears to be much less than the CR estimates.

And the installation costs includes their "certified" installers. You buy their product, they install it.

So while it's probably not the best idea for SoMD, if you live in Sunny SoCal where tile roofing is prevalent and shade trees overhanging your roof are not, this is looking to be an affordable alternative.

No doubt. If I lived somewhere with full sun all the time, I'd think about it. They certainly look better than traditional solar arrays on roofs.

Elon Musk is doing amazing things. The guy's a genius, but solar just isn't in the cards for me, and given the relatively cheap electricity we pay for, solar would need to come way down in price before it's feasible. It won't take long though.
 

Clem72

Well-Known Member
you can build your own

I follow a couple of guys on youtube that do just that. There's an aussie that has like 50kw of packs he built. But even if you can source the cells for free (from laptop batteries or some industrial application), and even if you treat it like a hobby and value your time completely for free, you still end up spending damn near as much as just buying one. Unfortunately any time you use more than two lithium cells together you need to add expensive charge leveling, control, and heat monitoring hardware.
 

BadGirl

I am so very blessed
Our second "$0.00" electric bill. We have a credit!

Before solar, our monthly bill for this timeframe would be in the $275-$300 range.
 

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itsbob

I bowl overhand
So someone mentioned their heat pump with electric backup can run them 500/mo. in the winter. Is this normal? I currently have an older heat pump with natural gas backup and my combined gas/electric bill is usually under 200 even in the worst winter.

What is the HSPF rating of your system? How warm did you keep it in the winter?

There's a few reasons your Emergency Heat can come on: temps below 25 - 30, an increase in heat needed more than 2 degrees (why heat pumps should be set and left alone, turning them on and off turns on E.Heat while trying to recover), or an unknown (until you get your next electric bill) failure of the Compressor/ Heat Pump itself.

Exceptionally cold months, turning your Heat Pump down while you're not home or at night for it to recover when you get home or wake up.. can drive your electric bill up a LOT,.. an unknown system failure where your system is running all month on E. Heat can triple your bill.
 

Gilligan

#*! boat!
PREMO Member
That would make me really nervous with a home that size.
I'd have to at least have a pellet somewhere in the home.
Plans to have, say a 30,000 Genny ?

Seeing as how our wood stove chimney (was fractured by the earthquake of 2011..but we didn't know it) took out the last house, the missus is understandably reluctant to have any kind of heat with "fire" in it in the new one.
 
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