From a purely EFFICIENCY point of view, using all that roof space for PV, at a return of around 15% (by the time you take out inter-cell space, inter-panel space etc), assuming you then use restive heating to heat water, it's still a low yield.
I have looked into this and done my homework about as best as I can figure.
For me personally, there are a number of factors that make PV the preferred method....
As far as roof space, I went and looked at some options for a patio roof this afternoon. I'll have 40 SqM facing north with that, another 50 Sqm on the shed and probably about 10 SqM on the house directly facing and 150?? sqm orientated east/west. -I- am NOT going to be short of roof area in any way shape or form!! :0)
From what I can look up, a 10Kw system of 250W panels is only going to take 65 Sqm of roof. Thats not going to be a problem and 10Kw is probably as much as I can use in reality.
The PV won't just be used for water heating. Once the water is up to temp I can switch that power to something else. I'm looking at a controller to say kick in the clothes dryer, run the pool pump ( when I put one it) run the AC or just back wind the meter for later use.
Far as I can see, when your tube heater had the tank boiling probably by 9am here in summer when it can already be 30oC easily, WTF is the thing going to do the rest of the day? Boil off water? Not even sure how they work once up to temp and with excess solar energy going onto them.
To me that's the thing, a solar water heater heats water, that's it. Nothing else. PV can do a lot more for me.
For heating water, with PV I don't have to change a thing. Can use my current heater and for me, a bit of wiring is a lot easier and cheaper than plumbing. I'm thinking of running a 2nd heater as well. This could be run as either a full temp heater to boost capacity or as a dump load pre heater feeding the existing tank. I'm not sure how much hot water I'm going to need as yet. Our old heater died a couple of years back and as I had in mind to move, I put in a tiny one that I got cheap to get us by. We are all looking forward to long hot showers and something we have never had before, a bath.
No idea what the usage will be as the "facilities" for bathing in the home are different as is the current family size.
Solar water heaters here are a LOT more exy than PV, used or new. For me putting up PV and wiring it is also far cheaper than plumbing and running pumps etc. It's also less difficult from an aesthetics POV.
One other thing for me is Oil heating. I have built all sorts of weird, wonderful and powerful oil burners and converted gas heaters. When our electric hot water blew I plumbed up the oil fired gas heater and we used that for a few days. Once up to heat the thing could keep up with the demand indefinitely.
When push comes to shove, my oil fired heaters will outdo any form of solar heating and the gap gets wider the worse the weather. :0)
Evacuated tubes (wet or heat-pipe) can give you around 4 times that, and achieve decent temperatures.
If I have 10 or even 5 Kw of solar on teh roof, I don't think there will be many days in the year I'll have to rely on grid power for hot water if I go a PV system. I figure about 30 a year max. With the feedback I can get the rest of the time, I think I'll be far better off in the big picture. If I double my tank capacity, I can probably go 5 days with water of sufficient temp before I have to boost from outside sources. That said, I also have my own generatorS I can and will hook into the grid power to backfeed or if I want direct feed. I'm going to set my lister genset up in the garage and put on a transfer switch so I will be self sufficient if need be and can generate power during rainy periods if I want to still offset my grid consumption.
Don't count on your old analogue meter staying there for too much longer. As soon as you start using it to YOUR benefit (like, reducing your power bill), they'll be out to change it over. Either because they think it's gone faulty (and reading less power than you're using) or that you're running it backwards (which they don't want!).
No, I'm sweating that's what will happen when the owners of the new place disconnect and I re connect. I have already said to the Mrs that I will want it in writing the meters won't be interfered with as a condition of who we go with. They have wanted to change them here where I am and do the bare minimum to comply with the law as far as notice and compliance. The letter I got said they needed to do safety checks and Maintenance. A call and some very specific questions which they skirted around ( telling me they KNOW people don't want these things) uncovered that their real intention was to take away my spinny meter and replace it with a smartarse meter.
One " Supervisor" I spoke to whom thought he had all the pat answers, went on about saving me money and checking my usage at any time and all the rest of their predictable and parroted crap they use world wide.
I said to him, you really expect me to believe your company is spending tens of millions on equipment and installation that is going to loose them tens to hundreds of millions in revenue by reducing your customers bills when they could spend nothing and make more? Do you really believe that or is that what you have been brainwashed to believe or are you just hoping I'm stupid enough to fall for it?
Then I got the bit about being able to monitor my homes power use even from my phone. By this time I'm asking the guy if he's for real? I said I have better things to do in my day than check what time is the cheapest to do a load of washing. And as for phones, if they don't have a 30" screen I'm not going to bother looking at them, I'll use my computer but again, WTF makes you think I want to be checking my power bill all day and have nothing more important to do with my time?
Good job this was over the phone and not in person or I may have been tempted to smack the guy for insulting the little intelligence I have.
I plan to cut a hole in the meter box, put a perspex panel over the meters so they can be read and then lock the box securely. Technically illegal here to deny them access however the amount of cases where they have illegally swapped meters with no notice would make any any action on their part a very unwise move in negative media coverage I would create let alone anything else.
There seem to be different interpretations of "net metering". A number of authorities add up the "numbers" and then charge you at their sell rate, or pay you at THEIR buy rate, on the net. That's not "net" in my view. Still, it's better than the alternative of selling ALL your power to them at their buy rate, and buying ALL your power from them at their sell rate!
Yeah, net to them means net profit and nothing else.
A big flaw I see in this net metering is Hot water.
Here off peak around the country is 11PM to 5am. where I am off peak is about 15C kwh all up. Where my father is it's about 20.
Almost universally, bar remote locations, the feed in tariff is 6-8C Kwh.
Therefor what happens is, you sell your solar at 8C kwh through the day but then even the cheapest buy back is 15C. Great deal for the power companies. NEVER seen them ever mention this little cash cow they have. Big Ra Ra about saving with solar but they have it sussed as always. They never make mistakes in the revenue improvement department.
Here I have the off peak connected and the heater coupled to the normal circuit. My current solar system is back feeding and winding the meter backwards so I get back what I give at the same rate which to me is only fair. Their malarkey about maintenance cost and distribution is just that, crap. It costs NOTHING to send the power I make next door or 10 houses up where it will be consumed because not everyone has solar and those that don't are more than putting in enough for maintenance. Of course that's just domestic, what about the megawatts used by factories and office blocks and people in units?
The power companies post tens of millions in net profit per QUARTER here. Can't tell me they need the money for maintenance and I'm doing them out of income when they are making all that profit. They want to jump on teh green bandwagon ( again purely for profit) then you stick to it. I'm making green power, saving loads of Co2 and all that garbage and also saving the company a heap of losses in transmission by giving them something they are selling every bit of at a LOWER cost than their own wholesale. If' its all about saving the planet and they charge so much more for " green " power, then why the heck aren't they paying me MORE for what I'm putting in not less!!
No, I have no compunctions about rewinding my meter what so ever.
The new place actually has one smart meter now on one of the 3 phases the home is wired into . Currently does the hot water peak and off peak, one leg of the AC and either the lighting or septic system.
First thing will be to remove everything from that phase including the water heater leaving only the AC which I need that leg being a 3 phase unit. That's OK, I'm happy to pay what I am here, about 150 a quarter just to keep from having to go off grid and not to arouse too much suspicion. The rest I'll move onto the other 2 phases which I'll identify to back feed. What I have looked up tells me that the smartarse meter on the place will register any back feed as a cost so I'll ignore that leg of the supply although If I am running the AC I can measure the draw on that leg and feed a limited supply to offset the grid cost.
Don't think I'll need to though. Should have the consumption low enough and I don't want a zero bill in fact.