Our Solar Electric Panels: Done!

I looked into the solar hot water when I got the PV array. The cost was about half, but IIRC, it made more sense at the time to get the PV array due to the tax credits and rebates that were in place. At least, over a 5 year period.

If all of my appliances weren't new or within their useful average lifetime, I would definitely look into other options for the hot water heater. It was replaced when I bought the house, 5.5 years ago. It's still got quite a bit of useful life left in it. Oil furnace I had replaced, and the A/C unit. I'm not sure how well the solar hot water would do, as half my entire roof (the whole front almost) is covered in panels. The rest is in the shade almost all day, until the leaves fall off the trees, or the sun dips beneath a neighbors tree late in the evening during summer.

NG isn't offered here (unfortunately), so I'd be stuck having to get propane, along with all the install costs for it. I think I checked before, and just to run 1 single line, it was like $200 for 20 feet. I'd rather not have another fuel tank in the back of the house, since the oil one is there already. If NG was an option, I'd have gone tankless already.

I like the idea of the heat recovery A/C unit. Maybe in another 5 years when the HWH is at the end of its average life, and the A/C unit is pretty close, I'll look into doing that type of setup. I believe that's similar to what they couple with GeoThermal for a lot of people.

 

dhanson -

I looked into that same water heater last year. How's it been working? Did you notice any lower electric usage after you installed it? IIRC, there are/were 2 manufacturers of that type of unit. I asked the salesman at Lowes about it when I was getting my new dishwasher, and he mentioned needing a certain sq ft of space in the room it's installed in. I think I'm a little short in that department based on where my current water heater is. However, if I'm close, it might still lower my usage when that time comes. The other options for me, are the 2 Icarius mentioned, or running multiple electric tankless in series. I'm leaning against the multiple tankless, due to the fact it would probably tap out the rest of the open spots in my breaker box. And at that point, the cost for install becomes a bit pricey, too.

 

Two words anyone in this situation: electric vehicle.

Instead of getting $0.03/kWh you get $KP/M, where
K = mi/kWh
P = $/gal
M = mpg in an HEV

E.g K = 3, P = 3.50, M = 50
Your electricity earns $3*3.50/50 = 10.5/50 = $0.21. So, $0.18/kWh extra.

 

geospring horsepucky - It's just a heat pump. If you know how a "split system" works with a heat pump on the ground outside of the house and the air handler inside you know how this water heater works. It's just a heat pump on a water heater with the "outside" being the air in the room and the "inside" being the water in the tank.

It uses 1/2 to 1/4 the energy of a resistant water heater based on the ambient heat in the room available to pump into the water. In the deep south in an unconditioned space that is likely to be 1/4 the energy usage. It's definitely cheaper than a gas water heater so I'm not sure if your 10 to 1 ratio is accurate.

I'm not using resistant heat for my house nor my water. I have a heat pump outside the house and a heat pump that is integrated in the water heater inside the house (but in an unconditioned space).

As to gas, I live far enough south that my heating needs are less and as I found it true in IA it's true in TN the utility companies want to charge a monthly fee to read the gas meter no matter if you use the gas or not. So if I use it for heating the house 2 months out of the year I'm paying a fee 12 months for 2 months use. That magnifies the cost of low usage natural gas greatly skewing the economic consideration for me. If I didn't have pay to not use it I wouldn't be so against natural gas. In 2009 in TN the charge was $6.90 a month plus tax for 0 therms used. In IA back in 2000 or thereabouts it was even more.

You might convince me that in northern states it's worth it to be nickle and dimed on monthly fees to get more efficient heating but I live far enough south that I don't need the heat enough to pay more for it and it's clearly cheaper for me to go electric here.

And fwiw the gas furnace was more than a decade old, as was the stand alone air conditioner and neither was high efficiency for their time so it made sense for me to go for a high efficiency heat pump and kill two birds with one stone.

 

I got mine at Lowes and it is the GE not the competitor's copy that was less efficient.

If you live in an apartment or otherwise have a water heater in an interior space the noise of the heat pump might be excessive but I can't hear it in the room beside the garage or the room above it. It is taller than any water heater you have I'd want at least 7 or 8 feet height and the normal 1 or 2 foot clearance around it. It doesn't need to be in a large room but it needs airflow to pull heat from so if it were in a small space it'd have to be a vented space that has good airflow.

I'm happy with it for several reasons

1. It's digital so I don't have to screw off access covers and reach past fiberglass insulation to change the water temp.

2. Because it's digital I don't have to guess at how I set the temp I've dialed it up 1 degree at a time until I found the temp that will just barely run out of hot water on my longest shower on the coldest of days. I can precisely tune it for summer vs winter instead of just dialing it somewhere near what I want.

3. It's not just a dumb digital it allows multiple modes including a vacation mode with a timer in days (no calender just a clock), a guest mode (super high recovery in case the house gets additional occupants temporarily or permanently at the cost of more resistant heat use), heat pump ontly, or heat pump + resistant with heat pump preferred. I leave it on heat pump only except when it gets below 40F outside as the incoming water and drafts influence my idea of how cold the "cold water" is.

4. It's air conditioning my garage which is both reducing temp and humidity in what was a mostly unconditioned space. The vast majority of the time that space was too warm anyway so it's almost always a plus.

I'm sure it's saving me money vs the resistant "high recovery" 50 gallon water heater it replaced base on the lovely energy guide sticker and energy star logo but I've made too many other improvements to the house around that time to have much data on exactly what it saved me.

 

Sounds like you have it dialed. In moderate climates heat pumps certainly make sense over resistance electri heat. Ground source and or hot water recovery is an added bonus.

Icarus

 

I've got a single family house, but my water heater, oil furnace, washing machine, and dryer are all in a room that's roughly 8x12, if I had to guess. The downside, is the water heater is in a space, that's just wide/deep enough to house it. There's maybe 5" of space around 3 sides of it. That is, unfortunately, the only place I can put it in that room feasibly. My ceiling isn't the full 8 foot in that room, but it should be tall enough to accommodate it. I originally talked to a plumbing company about more efficient water heating, and that's the unit they recommended based upon my setup.

It will definitely be on my list of items to look at when it comes time to replace my water heater, along with the heat recover A/C that icarus mentioned. Other than trying to figure out something for tankless, those two seem like my best options for upfront expenses. I will look into the solar hot water again then also. Who knows what technology might do in the next 5 years or so, maybe less if I get impatient .

Thanks for your feedback on the unit!

 

I'm not sure if I looked at the right thing but I tried googling it.

Is it for boilers? I have a forced air system, is that an option? The couple sites I looked at seemed to go right over my head lol

 

Congratulations. The key is conservation & efficiency. Energy not used is as important (perhaps more important) compared to what you generate. You need to obtain an efficiency rating for the house as a whole.

 

The GE unit I have is 61" tall but you need another 14" above it to be able to pull the filter out for cleaning. But ignoring airflow you have to be able to keep pipes/ceiling out of the way of the unit for 75" of vertical space. I have the water pipes doing a 90 degree turn right at the 14" mark above the tank and have maybe an 1/8th of an inch clearance to remove the filter.

Further if it's in a garage it's advisable to put the unit up on blocks or a metal stand to keep the electric elements above gas fumes (not applicable in a non garage installation).

Since I'm not height limited and it is in garage I have two layers of cement border that had been pulled up from the yard stacked in a nice circle under the water heater adding 4 to 5 inches of height. For gas water heaters they go for a 18" stand but I guess the risk is lower with electric. I know of a home near me where the water heater sparked a gas fire while an older gentleman was refueling a lawnmower. The house wasn't hurt at all (other than smoke and water damage) but the man died in the flames. My memory says he had an electric water heater but I'm not positive.

 

75" is definitely going to be close for me. IF I had to, I could cut out an opening above it in the ceiling. I've got a 2nd floor above that room, so there's some room between the ceiling and the floor as well. My tank right now is actually up on a platform built on 2x3 boards. I don't recall why we did this, but we did. Maybe to keep it up off the floor a little ways. My water pipes run above the drywall ceiling in that room.

I'm going to have someone price me out solar hot water again, to see what it would cost. Apparently they also have roof mount wind turbines now, so we will discuss that option as well. Since I have the Enginer kit ordered and needing installed, I'm not sure whether it would make much difference either way. The only plus I see with wind is I can sell the RECs, and I'm not sure I can do that with solar hot water.

 

OK we beat to death the nat gas vs electric stuff :focus:

I currently pay less than 10 cents per kWh. I don't have a south facing roof but I do live in a reasonable area for solar (don't have to worry about snow and it isn't overly hot like the desert southwest so panel/inverter efficiency will be better) and I have plenty of roof area to work with so cents per kWh are more important to me than the exact efficiency of the panels.

I don't have tons of money (in fact I'm on the poor end of the spectrum for US) when do we think PV solar will beat grid parity for $0.10 US per kWh?

The longer it takes to become affordable the lower my desired kW rating for the system will be though if smaller systems are less cost effective that may be a wash.

In fact if microinverters become the norm I'll probably end up with panels on the east and west roof surfaces. Considering the size of the roof and panels having decades of usable life I could see eventually filling the roof with cheap panels maybe even hand me down / used panels from others who have less roof space and decide to upgrade. Of course that is the extreme long term view.

Heck I even have space in the back yard that has a southern view and a parking area so I could do ground based solar tall enough to park a car under (some sort of carport like structure just vertical posts and solar panels no need to enclose the space in any way)

but for all of that to happen there has to be a used panel market and/or new panels have to get so cheap that I could afford to buy enough to start up an array.

 

That's a good point at the used panel market. I've often said that in 10 years, assuming I'm still in the house, if panel production rates could go up 50%, I'd be potentially willing to upgrade the panels for more production. The install shouldn't be nearly as bad, since everything is already done. But, then comes the concern of what do I do with the old panels, and how many people would be interested in panels that have reached that age.

If you can do the installation part yourself, you'd be saving a considerable amount of money, too. Ground mount would be better, if you are able to arrange the panels facing south vs using the roof. You really lose a lot of production if you can't. The last I checked, I thought prices were around $4/watt, but maybe that's lowered quite a bit as it was a year or so ago and my memory could be wrong.

 

The problem is I look at my electric bill and see just under 10 cents per kWh. So I need to translate from $ per installed watt to cents per kWh generated.

So say I buy a 6.5 kW system and it'll last decades (practically forever). If it cost me $4/watt that's a $24000 system. If I get 6500 kWh per year how many years do I divide by to get cents per kWh? Maybe I start with 10 for simple math.

$24000 / 10 years = $2400 / year. $2400 / 6500 kWh is .37 per kWh or four times the cost of my grid electricity. So I either have to be thinking much longer term or I have to get it much lower cost. Most likely much lower cost as I currently can't afford to prepay for 10 or more years of electricity.

I won't be getting a state rebate or utility rebate like Patrick got. I might get some federal rebate but it's possible my income will be too low to claim it (depends on if I'm working by the time I finally install panels)

 

10 years is a low estimate for life, by all accounts.

Do you have TOU rates available? Solar is better financially if you have TOU, since the panels generate during peak rates and generation is somewhat linked to higher peak usage.

 

I'd end up doing something like Patrick did with non flush mounting and wouldn't loose much (less than 10%, less than 5%?) by mounting them that way. See the panel inside the red box for an example of what I'm thinking for roof mounting.

 

I'm not suggesting the panels, inverter, or anything else would stop working during that 10 years, I just used 10 for quick, easy, dirty math.

Electricity is flat rate here and the buy price is below the cost of production I'm in one of the last few states to not have net metering. I pay very close to 10 cents a kWh no matter the month or time of day and until panels are so cheap I can literally cover every square inch of my roof I'll be avoiding producing any more than I use. Not just avoiding the yearly overproduction but making sure that not even one month out of the year do I overproduce. The upfront costs are too high and the utility here doesn't pay a rate that would reward overproduction.

Until panels/microinverters are so cheap I can add panels for next to nothing I intent to size the system such that my peak monthly output matches my lowest monthly electric bill.

Maybe that'll change if congress passes a national net metering bill but until then I have the dubious distinction of being in an area with good solar insolation but low electric rates and no pro PV policies.

 

You should easily get over 6500 kwh a year with that size system. The 6.5kw rating is the max peak production of the panels combined. In perfect weather (or near perfect, really), you'll get 6.5kw every hour. I max out at roughly 25-30kwh/day in the spring on a clear, sunny day. My 5.2kw system nets me around 6000 kwh a year. That includes short winter days, snow covered, not ideally situated production. If you have a larger system, plus better orientation, you should be easily able to pull 10,000 kwh annually from the unit, I'd guess.

Does your electric utility offer any rebates? Mine was 50% at the time of my install (got my system down to 20k out of pocket - a little less, as I had 2 companies price against each other). The rebate is down to around 25% or so now, due to demand since that time.