Newbie Electric Radiant Floor Heating tied with Solar

chases12 · September 2020

Hello to all.

I am new to the forum along with being new to the renewable energy movement.

I currently work for a solar distribution company installing solar arrays for schools. I am on the design side of aspects, but more or less just starting out.

My wife and I just sold our house and are looking to build once again. With being able to get panels and such at a discount through my work, I want to take advantage and use as much solar as I can for this new house.

My ideas are as follows:
2000 square foot house, 2x6 wall construction both interior and exterior walls.
Spray foam insulation
Crawlspace sealed and dried (Not heated)
Electric Radiant floor heating throughout the whole house (main heating source)
AC Furnace installed for back up heating through propane if need be.
Instant water heater (Found a unit to manipulate the water heater tanks to run directly off of solar http://techluck.com/index.php#buy
)
5 bed 2 1/2 bath 2 story rectangle design (Can send floor plans if need be)
We have 1 child with plans of having 3 total and would like to stay in this house extensively.
I do some mig welding on a small Forney 110V welder and do other projects in the garage as well.

I am wanting to size this correctly for a grid tied system using Microinverters to control the setup. I'm more of a fan of having them all run separately and the installation will be a diy up until it has to be connected to the grid.

I'm in the north east corner of Indiana.

Just needing some help sizing it correctly and making sure we're not buying way more than we need to so any help is greatly appreciated.

Ampster · September 2020

I have used electric radiant heating in small spaces like a tile floor bathroom. But not a whole house. A friend in Southern California who has an all electric home used heat pump water heater both as a source of domestic hot water and in the few months of winter, as a source for hydronic heating. In most cases, transferring heat is much more efficient that creating it with resistive elements. It may depend on where you are located. Wherever you are you are well advised to insulate since expenses designed to conserve energy are the most cost effective ways to save money. Any deeper discussion would require thermal energy skills which I do not have. Nor am I familiar with the climate of Indiana. Sizing an electric instant water heater is significantly different than a heat pump water heater in terms of Amps.
I should mention this, and excuse me if you already know this, but the microinverters will only work when they are connected to the grid. You can configure them to sync to the grid in order to operate and with an Envoy they can be configured for Non Export. I do not understand what you mean when you say you want the micro inverters to control the setup?

BB. · September 2020

In general, you are best to start with conservation (design on home on lot, summer shading/winter sun in through windows, etc.). There is lots of information out there on green building/insulation techniques.

For heating, looking at a heat pump system (air source is generally more cost effective vs ground source)... Depending on your weather and requirements, a heat pump in a >~50F ambient is 2-3x more efficient vs resistance heating. As you get below freezing, then other heat source(s) are generally needed (I am not a heating engineer--Lots of interesting research ahead).

There are other ways of saving money too... For modern homes that are tightly sealed--Then you probably want an air exchange system to conserve energy:

https://www.ecohome.net/guides/2362/ventilation-air-exchangers/

Using Mini-Split Heat Pump systems have been pretty popular for heating and cooling. And you don't have to run ducts throughout the home (and the additional air leaks and insulation that come with ducting).

Are you going to be tied the "grid" (utility power)? Or are you looking to be "off the grid" (solar panels+solar charger+battery bank+AC inverter+backup genset, etc.)?

In general, if you are looking for off grid power--Keeping your power usage in the 3.3 to 10 kWH per day (~100-300 kWH per month) is where you want to aim for. A typical North American home uses in the range of 500-1,000 kWH per month.

The other issue is how much sun do you have... For example, Fort Wayne Il, fixed array, facing south:
http://www.solarelectricityhandbook.com/solar-irradiance.html

Fort Wayne
Average Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 49° angle:
(For best year-round performance)

Jan	Feb	Mar	Apr	May	Jun
3.11	3.61	4.16	4.60	4.82	5.20
Jul	Aug	Sep	Oct	Nov	Dec
5.33	4.99	4.86	4.00	2.71	2.49

Just to give you a very rough idea of what a 500 kWH per month electrical usage for a Grid Tied system could look like:

500 kWH per month * 1/30 days per month = 16.7 kWH per day = 16,700 WH per day
Say a minimum of 4 hours per day of sun
16,700 WH per day * 1/0.77 GT solar system eff * 1/4.0 hours of sun per day (average) = 4,175 Watt array
If you use 300 Watt solar panels:
4,175 Watt array * 1/300 Watts per panel = 14 panels

If you are looking for Grid Tied Solar, you will have to find out from your utility what the billing plan is for GT solar... It is not always "obvious" what the final numbers will look like (Time of Use billing, monthly or yearly true-up of energy usage, monthly minimum charges, etc.).

And 500 kWH per month is a pure guess... Look at your old power bills and see how much you really use. And 500 kWH per month--With radiant heat/hot water/cooking (vs propane)--You might have to work real hard to keep your electrical usage that low for a 5 bedroom home.

Working with architects and contractors that are familiar with solar/alternative energy home design (as needed) should be able to give you much more accurate numbers for your design and energy needs.

-Bill

lucman2 · September 2020

Look into heat pumps, they are capable of COP of 3 where as electric is only 1. There are several air to water heat pumps (SpacePak Solstice & Sanden) available that would be suitable for running hot water radiant in your floors with much higher efficiency. Or you could use a hydro air system for heat and a/c.

mike95490 · September 2020

Agreed. Look into central heat pump, or mini-split heat pumps. keep a propane backup too, if your power grid goes anything like California is going.

How long have you been installing microinverters ? Had any batches of bad ones ?

New_Mexico_Will · September 2020

I'm definitely not on the cutting edge of construction, but how does a radiant floor work with a crawlspace? I've only seen them in slabs.

mcgivor · September 2020

New_Mexico_Will said:

I'm definitely not on the cutting edge of construction, but how does a radiant floor work with a crawlspace? I've only seen them in slabs.

Skim coat with a styrofoam sub floor, not the best because the thermal mass is reduced, a proper slab would retain heat for a longer period, a heat pump with slab heating would be ideal, not a retrofit opinion however.

chases12 · September 2020

I greatly greatly appreciate all of the feedback. I did some calculations myself for the consumption of the floor heat and the numbers I was retaining with the heat loss calculations of my system came around 7000KWH/ month. That's a lot of energy and to offset that completely with a grid tied system and the other calculations provided above, I would need a 232 panel array and isn't feasible for mostly anyone.

I am going to use the radiant electric floor heat in given areas (Bathrooms, kitchen, etc.) for supplemental heat and comfortability and I do like the idea of mini split systems for their efficiency, but don't like how there would need to be so many for our setup.

I will look into heat pumps with the propane furnace as a backup. We may also change the design the foundation to a slab with insulation on the foundation walls as I need to research more ideas in that area.

I am still in debate with going with an instant water heater or electric water tanks for the setup. For the instant water heater, my plumber mentioned they run more efficiently through propane heating source rather than electric but don't want many appliances on propane. On the other hand, there are units out there like this http://techluck.com/index.php#buy that hook directly to the heating elements for the water tanks and would like to designate some panels for that purpose as well.

As far as micro inverters, I was under the impression they control at 1 panel level meaning if there is shade on a small portion of the array, it doesn't bog down the remaining unshaded panels and makes those perform at their peak. That was my impression of microinverters. What are the pros and cons of a central inverter and microinverters?

I will be grid tied until the battery industry is a bit better and longer lasting chemistries. With the advancement in electric vehicles, I feel there will be a big swing in the battery technology and would like to wait a bit until such batteries are researched and tested. Until then, I would have no problem switching to off grid and doing the overhaul of the array at that point.

Dave Angelini · September 2020

For Offgrid we often install a combination of solar collector heated and gas heated radiant. We try to use as little electricity in winter as we can design for to keep costing realistic. We do this because it is winter and we want to always minimize genset use.

Grid tie you can really do whatever you want. You can have shaded panels that we would never do offgrid. Same with solar. We would build a ground mount for solar as the only thing we want on a roof is rain or snow.

Just some contrast for you. Good Luck!

chases12 · October 2020

So I looked into the heat pump unit and was curious of what consumption that would take on our system. It seems as if I could use radiant floor heat in certain areas for the main heat and have the heat pump in conjunction with the radiant floor heat.

chases12 · December 2020

So I have been doing loads of research and seem to be dreaming up this house with a lot of demand on the electrical system. Our goals for this house is to be energy efficient using mainly solar but grid tied for now...

So our electric demands are as follows:
- Electric radiant floor heating by Warmly Yours. Uses 15W/sqft having around 2500 sqft of livable heating floor space. Thats in a 240V wires.
- Tankless hot water heaters. 3.5 bathrooms ( 1 master bath, 2 full baths and 1 half bath) Wanting to possibly use point use instead of a whole house tankless setup (match the demands per area with the gpm of the unit we choose) Our incoming water temp for our zone in north east indiana is around 47 degrees.
- Solar amperage for 72 panel of 325W modules using the new Enphase Iq8 micro's when they come out. They're 9 panels per breaker having around 11 amps per string and having 8 strings resulting about 88 amps for the solar setup.
-The normal house electrical demand as per usual.

So my question and advice seeking is, how much amp service can I get and would the solar be able to handle these items with how many panels I am wanting? I've done a heat loss calculations and will be applying a more Passive house sealed construction with Zip R sheathing setup and other air and water tightening techniques for this house.

BB. · December 2020

If you can go with heat pump heating (and cooling if needed)--The heat pumps are generally 2-3x more efficient than the standard resistance heater (more efficient to move the "heat" from outside to inside using a "refrigeration compressor", than to burn Watts heating an element).e

Of course, there are "details" to any answer... Very cold weather (freezing and below), heat pumps become less efficient. So lots engineering/planning work would be needed.

I am assuming you are looking at a Grid Tied inverter system (more efficient, least cost, little maintenance vs battery based hybrid inverter systems).

The issue with tankless electric water heaters--The draw a very large amount of current--And the cycling on/off the heaters can cause noticeable (and sometimes objectionable) "blinking" of the lights. With modern LED fixtures--It is possible that they will be less susceptible to variable output vs the old filament based lamps (and florescent, etc.).

Why are you looking at tankless electric water heaters vs just normal tanked heaters. The efficiency is about the same (both are ~100% efficient heating)--Of course you have some losses due to heat loss through insulation and hot water in pipes (and in a circulation system if you want instant hot water at the tap).

You also need to work with your electrical utility... An >10,000 Watt GT solar system may trip further reviews, possible transformer/distribution system upgrades by the utility... Even your home, if you have an >200 Amp main panel may trigger an engineering upgrade too... If you add an electric vehicle charging station--Another energy sink.

In general, a typical home in your area may be 1,000 kWH per month... And down in Texas with full A/C in summer--Perhaps >3,000 kWH per month.

And will you have a genset for emergency/backup power? Will it power a subset of your home--Or do you want it all (water heaters, floor heating, non-propane appliances, etc.).

The genset itself will not be cheap (if a large unit)--You may have issues with backup genset on site--And fuel issues (propane, diesel, etc.).

Is there anyone in your area that has designed/built a home in the class you are looking at?

Also--There is a big "green push" in parts of the USA. And that can range from prohibiting Natural Gas in new homes/businesses (shakes head). And eye watering electric bills for "green power". While you may have reasonably priced power now--Looking at conservation & energy efficiency now can save you a bunch of money in the future.

Baseline is only ~300 kWH per month... So you are looking at $0.20 to $0.40 per kWH (winter/summer/off peak thru peak.

For folks that are paying $0.10 to $0.20 per kWH--There are going to be some big shocks if renewable energy is legislated in their regions.

GT power is pretty cheap to generate (~$0.10 per kWH is certainly not difficult). But utilities are starting to change their billing plans to change the economics of GT solar power... Higher per month fixed costs. Only "paying" for generation costs (about 1/2 the total $/kWH charges) or even "outlawing" new GT Solar connections. In a few areas, people got permits to install GT solar, but the utility refused to allow connections to the GT solar farm "because"...

In our region, our utility will "grandfather" existing systems for 10 years (rate plan choice)... After that, the reserve the right to change the agreement (through the state PUC).

I highly recommend that you look at conservation/insulation/etc. first. lt could save you much money down the road.

-Bill

My present electrical rates (northern California):

https://www.pge.com/tariffs/assets/pdf/tariffbook/ELEC_SCHEDS_E-6.pdf

(T) TOTAL RATES Total Energy Rates $ per kWh)
PEAK PART-PEAK OFF-PEAK
Summer Baseline Usage $0.40545 (I) $0.28701 (I) $0.21179 (I)
Over 100% of Baseline $0.49198 (I) $0.37354 (I) $0.29832 (I)

Winter Baseline Usage – $0.23296 (I) $0.21613 (I)
Over 100% of Baseline – $0.31949 (I) $0.30266 (I)

TIME PERIODS: Times of the year and times of the day are defined as follows:
Summer (service from May 1 through October 31):

Peak: 1:00 p.m. to 7:00 p.m. Monday through Friday
Partial-Peak: 10:00 a.m. to 1:00 p.m. AND 7:00 p.m. to 9:00 p.m. Monday through Friday Plus 5:00 p.m. to 8:00 p.m. Saturday and Sunday

Off-Peak: All other times including Holidays. Winter (service from November 1 through April 30): Partial-Peak: 5:00 p.m. to 8:00 p.m. Monday through Friday Off-Peak:

All other times including Holidays. Holidays: “Holidays” for the purposes of this rate schedule are New Year’s Day, President’s Day, Memorial Day, Independence Day, Labor Day, Veterans Day, Thanksgiving Day, and Christmas Day. The dates will be those on which the holidays are legally observed.

BB. · December 2020

Just in case, PG&E just got another 8% electric rate increase approval today (over what I just posted)... And they promise to not kill another 120 customers over the next few years (wildfires sparked by poor maintenance of transmission lines).

Of course, they already promised not to blow up another neighborhood and kill 8 people with a natural gas pipeline explosion due to faulty maintenance/records since 2010...

https://www.sfgate.com/news/article/PG-E-s-household-customers-facing-8-increase-in-15774384.php

https://en.wikipedia.org/wiki/San_Bruno_pipeline_explosion

-Bill

lucman2 · December 2020

chases12 said:

Hello to all.

I am new to the forum along with being new to the renewable energy movement.

I currently work for a solar distribution company installing solar arrays for schools. I am on the design side of aspects, but more or less just starting out.

My wife and I just sold our house and are looking to build once again. With being able to get panels and such at a discount through my work, I want to take advantage and use as much solar as I can for this new house.

My ideas are as follows:
2000 square foot house, 2x6 wall construction both interior and exterior walls.
Spray foam insulation
Crawlspace sealed and dried (Not heated)
Electric Radiant floor heating throughout the whole house (main heating source)
AC Furnace installed for back up heating through propane if need be.
Instant water heater (Found a unit to manipulate the water heater tanks to run directly off of solar http://techluck.com/index.php#buy
)
5 bed 2 1/2 bath 2 story rectangle design (Can send floor plans if need be)
We have 1 child with plans of having 3 total and would like to stay in this house extensively.
I do some mig welding on a small Forney 110V welder and do other projects in the garage as well.

I am wanting to size this correctly for a grid tied system using Microinverters to control the setup. I'm more of a fan of having them all run separately and the installation will be a diy up until it has to be connected to the grid.

I'm in the north east corner of Indiana.

Just needing some help sizing it correctly and making sure we're not buying way more than we need to so any help is greatly appreciated.

Take a look at the Spacpak Solstace air to water heat pump for your space heating & cooling and possibly domestic hot water.
Heat pumps have higher COP's than straight electric even at sub 0 temps. In my opinion anything straight resistance is a poor use of solar power when heatpumps have COP's of over 3 and resistance has a COP of 1. I don't recommend Geothermal because of the initial cost and COP's start dropping in the cold month's of winter as the heat is removed from the ground or water table.
Sanden also makes an air to water heatpump for domestic HW, you could also possibly use multiple Sanden units for radiant space conditioning.

Dave Angelini · December 2020

8% up huh Bill ! And they turn it off when it is 100f or windy? I have my spotting scope set-up looking out 20 miles where their lines are. They still have not cleared the brush under them in 20 years.

So the OP is in California? Unless he is coastal the offgrid method will be far cheaper and probably less pollution. Solar domestic hot water in a 50 to 75 gallon tank backed up by gas. 6 good collectors with drainback if he freezes. A few grundfos pumps. All of it can run off less than a couple hundred watts. Even less power if he get creative with direct venting.

It is getting harder to find good plumbers who know solar domestic and so heat pumps do make sense except for offgrid. If you did it offgrid, it would be fine as long as you had a complete back-up for winter/storms when you need to save the electrons.

Dave Angelini · December 2020

If he lives in Berkeley or SF he probably can only use electricity. No new construction with any kind of gas.

BB. · December 2020

Chases12 is "I'm in the north east corner of Indiana."

It sounds like he has an aversion to use of propane... I have met a few people that prefer electricity over natural gas or propane... For propane, other than the costs/tank(s) type issues--There is (as I understand) the real issue of propane being heavier than air and having propane settle into low spots is a real issue (natural gas is mostly methane which is lighter than air and will tend to dissipate better).

And in much of the USA, vent-less (unvented) propane/natural gas heaters are allowed... But I would certainly avoid them in my home (in California, one of the few states where V-L heaters are outlawed--sort of).

https://www.ventless-gas-fireplaces.com/ventless_products_code_information.html

I don't trust our state PUC (public utilities commission) at all... Seems to be all political and about the money (surprise). For water, our water costs have gone up by 7 times or so in SF Bay area--Much of it do to earthquake proofing/rebuilding our water infrastructure (100 years old and hardly any maintenance during that time?). Much of SF water comes from the mountains near Yosemite.

https://gizmodo.com/how-san-franciscos-clean-drinking-water-destroyed-the-1605614294

Anyway... I suggest conservation as a start for any new/major home upgrade now. The cost and difficulties of energy (and water?) appear to only be getting worse in the future. For a person that has never done any conservation projects in their home--I suggest it is not that difficult to reduce energy usage by 1/2... However, the expenses for new appliances/furnace/heat pumps/insulation, etc. are not cheap--But they tend to be one time costs--Vs the monthly power costs (and/or the cost of off grid solar systems and their maintenance costs for "larger" systems).

Grid Tied Solar still leaves you connected to the grid and the politics of the grid. At any time, the powers that be can change the agreement.

Folks like Dave living off grid (battery based solar) don't have the politics of utilities issues (at least not yet)--But are still impacted by state policies (wildfires from power distribution failures, poor forest/lands management, etc.)...

-Bill

Dave Angelini · December 2020

Definitely vent a gas water heater. Direct vent is a tank heater (perfect for offgrid) that can be vented out a side wall or straight up. It uses zero electricity, gets combustion air from outside, is sealed combustion for a garage, and has none of tankless issues that many find out about after they buy one. Electric or gas tankless...not a fan!

When we get impacted by any of the crazy stuff west of us, it is either Nevada or Texas. I am on our Fire council here in the county trying to get them to harden the town. If they lose the town, like Paradise we will leave. Gruesom has mandated our 8 bed hospital to be earthquake safe and the tax gets voted down by the ranchers and farmers in our Red county. So that may force a move east.

Maybe we will be neighbors Bill? With all of the C19 in Clarke county (out of Vegas) we are looking again at Carson area but really want out of the snow. I keep my reference on a place where I put my parents when they got too old and demented. It was called the Remington near San Diego. It had it all from a house, everything in between, to memory care. A Vons across the street. Great Rock shows at a casino. Did not need to drive.

Edit: Except it was in California....

Dave Angelini · December 2020

I think You are mixing up Vent Free and Direct Vent Bill.

BB. · December 2020

I don't think so... Un-vented dumps combustion products directly into the room (typically catalytic heaters--But also includes gas stoves).

Vented (direct, power vented, condensing, etc.) have combustion products going out a flue/directly outside. There are some sealed units that also take outside air too (avoid taking conditioned air into the "heater")--Direct Vent(?)...

In California (and Texas/Utah/other states?), we now have NOx smog control regulations even on gas water heaters (and HVAC in general coming/now?).

-Bill

Dave Angelini · December 2020

Well the ones I wrote about Direct Vent are extremely low NOX and I have been using them in dozens of california offgrid homes. You can buy them special order at Lowes or Home Depot. Read it again boss....Your question mark makes me think we are saying the same thing? Cheers! Some of the Direct Vent models also have a hydronic loop built-in for radiant or solar input/output. A 40 or 50 gal is around a grand up.

BB. · December 2020

I was unclear if direct vent was both inlet and outlet vented outside, or only a combustion outlet outside was also a "direct vent"...

California required low NOx water heater since something like 2008 or so (perhaps earlier too?). I see Texas and Utah (possibly others too?) in the last few years are starting to require low NOx too.

-Bill

Dave Angelini · December 2020

Image: https://us.v-cdn.net/6024911/uploads/editor/uy/a6sqhlsst8zu.png

Yes

Direct Vent from American water heaters, AO Smith, and a few others use combustion air and exhaust from outside the structure.
They meet Cal requirements back to 2002 when I did my first hydronic here. Just bought one for a client last month.

For Offgrid, building a house, or retrofitting. With a tank 40 feet or so up the hill, one can take a hot shower without any electricity.

You can see the 2 flues in the pix.

chases12 · December 2020

Thanks to all for the ideas and support for my new construction home.

Bill: to further answer or comment on your remarks, I am against propane for both the environment and the monthly or one time reoccurring bill that we are trying to eliminate.

As far as insulation: the new construction house is going under details of air tightness and other potential leaks. We are planning on using the ZIP R sheathing and the ZIP System for our home along with an insulated foundation (slab on grade) and 2x6 or 2x8 walls, spray foam, and other sealed techniques. I've been watching a lot of Matt Risinger on YouTube for his builds and how he constructions them for more efficiency. I'm still stuck on the heating elements in the house due to my aversion to propane. The heat pump does well under the right conditions but with a house of 5, I don't necessarily want to take any chances. Could I do a possible hybrid using electric radiant floor heat in the bedrooms and bathrooms and let the heat pump take care of the rest of the house? It's a 2500 sqft 2 story house. So again, the heating element is still a big question mark.

As far as the water heater, I don't like the fact of standby heat loss with electric water tanks. Plus we have a 50 gallon hot water with only 1 child at the moment, and we run out of that daily scurrying in the shower to get the last bit of hot water. So for that, maybe double or triple up the 50 gallon tanks and throw an insulated heat blanket on them? If so, then I would have to find some room in the floor plan to stuff those. Another aspect on the tankless is I can have hot water for as long as I like, theoretically. So not sure on there. My cousin who is an electrician has gone through the amp draws of the units I am looking at and suggest a 400 amp service for the house to accommodate for this.

I do appreciate all of the feed back greatly. We have a lot of time to plan and build and would want this house to be efficient as possible without sacrificing the daily habits. We don't use a lot of energy either. I think in our old house, we used maybe 700kwh a month on average so way below the average we have now.

We are looking into an off grid set up, but want to wait a little until the battery technology advances but would like to set up a grid tied system to have the advantage to switch over at a later date.

Dave Angelini · December 2020

Sorry about derailing your post! You should stay with the grid. Offgrid should only be done for specific reasons and both eyes wide open.

That said, very hard to go back to the grid life. Love this way too much! Good Luck!

chases12 · December 2020

Dave Angelini said:

Sorry about derailing your post! You should stay with the grid. Offgrid should only be done for specific reasons and both eyes wide open.

That said, very hard to go back to the grid life. Love this way too much! Good Luck!

I appreciate your feedback. My uncle is going off grid in about a year or so, but he also is a single individual and its easier to compensate for yourself on the consumption rather than trying to convince your wife or the kids to cut back on things they think is normal, you know! I appreciate your feed back a lot though so keep it coming please.

BB. · December 2020

You can always install baseboard (and central) heaters... And just not use them while the heat pump(s) are working. Many heat pump installations (as I understand) will include electric backup heaters (especially for cold climates).

I tell folks to figure on $1 to $2 per kWH for off grid electricity (people that live there 12 months out of the year typically have a bit lower costs vs those doing less than 9 months a year--Normally, you store only ~2 days of energy in batteries (hot water tanks, etc.). Solar electric tends to over produce in the summer (unless you use A/C) because of lots of sun... And under produce in the winter (less sun, more shade from trees/hills/etc.). For winter, you either (and frequently both) have to over design the solar power system to harvest your winter needs, and need alternate power (wood, propane, genset) to make up for "dark weather".

If you do everything yourself, buy for good prices, and manage your power closely (use power when sun is available, cut back when power is not)--You can get possibly down to $0.50 per kWH. But that is a personal choice (how much "active energy management" you want to do--Or do you want it "to work" and not have to manage the personal energy use of 5 people in your home).

For heating--Solar heating via thermal panels may be of interest to you... There are some interesting products and projects.

www.solarroofs.com

https://www.arttec.net/Solar/BarnHeat.html

https://www.builditsolar.com/Projects/SpaceHeating/SolarShed/solarshed.htm

https://www.ecohome.net/guides/2276/choosing-between-an-hrv-and-an-erv/ (heat recovery ventilators)

The issue with solar thermal systems is they can be a plumbing nightmare (leaks, failing pumps, air in system, etc.).

So, are you willing to pay a "premium" for electricity (5x your present electric rates) for the privilege of generating your own power... And doing your own maintenance and parts replacement... Batteries can last 3-5 years for "cheap lead acid"... 7-10 years for more expensive lead acid batteries, or >15 years for forklift type batteries.

And there are LiFePO4 (lithium iron phosphate) batteries... They are getting pretty close to the ideal battery (long cycle life, efficient, no maintenance, light weight, work nicely in warm climates). Downsides include high upfront costs (can be less lifetime costs because of long life), and you have to keep them "warm" (typically 40F or warmer, cannot charge if less than 35F or so). Also, I suggest that you put Lithium batteries in a separate outbuilding. LiFePO4 batteries are relatively safe, but if there is a fire, there can be some very hazardous fumes that can mean the room/building needs to be demolished (cannot be cleaned).... Outbuildings for solar power/batteries/genset/fuel are not a bad thing anyways--Stuff happens.

And there is always the debate between ground mount vs roof mount panels...

Be really diligent on your power costs... Design the system, cost the components, add maintenance (new batteries every 5-8 years, new electronics every 10+ years, solar panels 25+ years? The occasional Oh Heck--Visitors too battery bank dead and "killed" batteries, local lightning strike took out AC inverter, etc.)

It is almost always cheaper to conserve energy than to generate it. When you have alternatives such as a heat pump system that can cut your electric heating energy usage by 2/3rds in moderate climates... That is a win for me. Some Heat Pump Systems can also provide Hot Water too.

But, I do agree that there are downsides to this stuff too... For example, there are Heat Pump based water heaters (and they frequently had resistance heaters for backup)--And they also provided "free" cooling and humidification (if you needed that, great. If not, then venting outside air may be needed). And some companies went out of business, or stopped making the products (one story I heard was they had a hard time finding service techs that could work on Heat Pump systems).

And systems like ground sourced heat pump systems had issues... Takes quite a bit of energy to circulate water in the earth field... Maintenance, etc...

Air Sourced heat pumps are becoming much more popular (no expensive drilling/digging). And with the Mini-Splits heat pump systems, no whole home ducting/heat losses/insulation issues.

Even the HVR (heat recovery ventilation) systems have energy drawbacks... They can take 1,000 Watts (guess) just to circulate the air for the "free" heating/cooling...

If you are off grid--Looking for "off grid" friendly products... Generally low surge current/low power (relative to typical stuff). Solar friendly well pumps--Limited to 1,000 Watts or less, some can connect directly to their own solar array--You pump into a cistern, and use a smaller pump to pressurize the home.

We have a FAQ that has been added to over the years. Lots of information that may peak your interest.

https://forum.solar-electric.com/discussion/4426/working-thread-for-solar-beginner-post-faq/p1

For folks that do have power lines available (or can get power for less than $20,000 today)--I suggest that the property may be worth more in the future for buyers that don't really want off grid power. I suggest that $20,000 "invested" in power lines adds to the property value... $20,000+ "invested" in off grid power for your home--May be difficult to find a buyer willing to pay that amount... And 40 years down the road, will you and/or your spouse be able to continue operating/maintaining the off grid power system...

Bringing power to a remote/unserved site--In earlier times, there were subsidies (rural electrification programs)... Today, it seems to be getting more difficult and expensive to bring power in to remote sites. And I fear that several decades in the future, it will be even more expensive or even impossible to bring in utility power (utilities see remote sites and cost sinks to maintain)...

This is all a combination of personal choices and where you live.... Just one person's suggestions as too what may, or may not, work for you.

-Bill

ziansur · November 2022

Hello. My wife and I are having a passive home built next summer. The house will be located in the Drake, Colorado, at about 7000 feet. climate zone 5. The home will have a slab on grade foundation. The home construction method will be a modified post and beam structure with straw bale infill(non-load bearing). The home will be one level. There will be no furnace and no AC. Heating would be via a wood stove insert into a fireplace. The goal is for a tight envelope. Walls will be approximately R-40 with the straw bale infill(this is covered with a welded wire material and then hydraulic lime plaster applied to both sides) and attic probably at least R-50? The roof will be a standing seam metal roof. We plan on having a 6-8 KW grid-tied solar panel system. There is no natural gas available. Propane is an option but my wife and I don’t like the cost, so our plan was to use the electricity.

BB. · November 2022

Welcome to the forum Ziansur,

Normally, at this point, I would suggest you start your own thread to avoid confusion/mixing of your needs/questions with the original poster's.

However, there was a lot of information/discussion in this thread about alternative power, ventilation for tightly sealed homes, etc. And questions about energy needs (heating, cooking, hot water, etc.).

Normally, I suggest if you have utility power, you stick with utility power. Going off grid is not cheap, and comes with its own issues. And go with a nice genset/stored fuel for places with cold weather and/or poor sun in winter.

And things are getting really crazy right now... Between California burning, and our president going with a "no drill"/"no coal"/what about nuclear policies... It is making utility power looking more expensive and unreliable.

Using an induction stove can be very efficient for electricity (need pots/pans that are rated for use with induction cook tops).

Just to use a nearby city for a quick look at solar... Boulder Co., fixed array facing south:

http://www.solarelectricityhandbook.com/solar-irradiance.html

Boulder
Average Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 50° angle:
(For best year-round performance)

Jan	Feb	Mar	Apr	May	Jun
4.10	4.69	5.41	5.34	5.52	5.84
Jul	Aug	Sep	Oct	Nov	Dec
5.74	5.44	5.54	5.15	4.21	4.02

Assuming similar weather/no shading of array, 4 hours of sun per day is still pretty reasonable. So Solar (Grid Tied, Off Grid, solar hot water/heating) looks pretty reasonable. Summer is not that sunny (high clouds?).

Grid Tied solar--This is a "political animal"... In states that have pushed for GT Solar (lots of subsidies, rate plan subsidies, etc.) have really pushed the utilities into high prices (in California we are in the $0.30 to $0.40 per kWH hour and heading higher/less reliable). At some point (especially rural areas that take longer to bring power back online)--You are looking at some sort of backup/stored power--For home safety (freezing weather, freezing pipes, having some power for lights, cooking, heating, etc. during power failures). And some states have outlawed, or through high cost rate plans (economically unfeasible)... Even if you choose to avoid propane--I would suggest that the home be designed to allow an easy propane retrofit a decade or so down the road (just looking at the politics).

I think you will need to look at some sort of stored energy... Batteries, perhaps 2-3 days of stored energy. Propane is the only long term/low maintenance/virtually infinite life of stored fueled option. Gasoline and Diesel have limited storage (a year for gasoline, perhaps longer for diesel). Some stored fuel for a car can be nice (bug out if needed... Ability to still shop at major stores for food/etc. during area power outages in a rural area).

I don't know the answers. Just guessing at a possible future.

Since you have grid power--Conservation is key to saving money and reducing needs for stored energy. I am not sure of the efficiency of fire place inserts vs a free standing wood stove (plus fans/ducting for moving hot air from the stove around home). Otherwise, if you need backup heating--Heat pump (mini-split heat pump) is a good alternative (1/3rd the electricity vs resistance type heating).

https://forum.solar-electric.com/discussion/23007/mini-split-update-for-offgrid/p1

Having a weatherized (or possibly even heated) shed for genset/batteries/etc. separate but near the home... If not now, at least in the plans (if needed) for the future...

I don't think we will go 100% electric cars, no fossil fuels (gas, oil, natural gas, propane, etc.) as the present electric infrastructure is not capable of supporting the dramatically larger loads (something like 3x larger grid needed). And much of the grid is still powered by fossil fuels and nuclear. The present trajectory does not include wind or solar for supplying base loads--And, at this point, utility scale energy storage (i.e., batteries) are still way off in the future (if ever economically possible/practicable).

With a new home design/construction--I would suggest at least preparing the home for alternative power sources and high efficiency now. Even if you choose not to implement at this time (such as propane/backup genset/etc.). GT Solar--Sure--If it makes economic sense for you today...

-Bill

Dave Angelini · November 2022

Along with Bill for the ride, how remote is it ? It looks pretty small town in Drake? If this is a full time grid-tie home you really need to consider it like an Offgrid home. Have 2+ ways to heat air, water, and make electricity.

It could take a month or more for help when you are remote. That might be good though...
As far as the current group thought on energy, "not saving the good wine here"

ziansur · November 2022

Bill "moderator B... Never mind this poster. Just a spammer out of India.

Newbie Electric Radiant Floor Heating tied with Solar

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Fort Wayne
Average Solar Insolation figures

Boulder
Average Solar Insolation figures

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Newbie Electric Radiant Floor Heating tied with Solar

Comments

Fort WayneAverage Solar Insolation figures

BoulderAverage Solar Insolation figures

Categories

Fort Wayne
Average Solar Insolation figures

Boulder
Average Solar Insolation figures