Dipping a big toe in solar
I was wondering if there was a good guesstimate tool for helping to figure out “how much Solar I need”?
I am thinking about adding Solar to a spec. house and was interested in Solar since the price point has dropped so much. I will be doing the panel install myself with my crew and have the electrician wire it up.
My question revolves around what “benchmark” to shoot for, as there are so many; zero-energy building, also known as a zero net energy (ZNE) building, net-zero energy building (NZEB), or net zero building, “energy-plus buildings” and buildings that consume slightly more energy than they produce are called “near-zero energy buildings” or “ultra-low energy houses”.
My roof is shed in design and pitched at 14 degrees and has a 28′ width and depending on the length somewhere between 48′ and 64′ of length.
I am looking at one 8 string system and was wondering why wouldn’t I just cover the entire roof with solar which would give me @ 16000 watts?
The house will be highly insulated/sealed/Manual J’d/ Lstibureked/heat pump HW and @ 3500 sq. ft., I ASSUME that the house will have an electric demand of no more than 1250 kwh per month which puts me at @ 9yrs payback (simple) @ .12 cents per kwh.
I also would like to hear if any other spec builders out there think the extra 24-30 k $ spent would be a wash, or if new homeowners would perceive enough “value” to get that money and perhaps a 10% ROI on my end for the additional monies/time invested.
Thanks for your insights!
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Replies
Leo,
The most important factor in your decision is the net-metering contract that is offered by your local utility.
Some utilities offer a generous net-metering contract that not only credits homeowners for the full retail price for their PV production, but even sends an annual check to the homeowner for any extra electricity that the PV system feeds into the grid.
However, most net-metering contracts set the meter to zero once a year, and refuse to send a check to homeowners for excess PV production. If that's the case in your area, it makes no sense to oversize your PV system -- since any excess production is merely a donation to the utility.
There is a third category of utilities -- the scrooges which impose high connection fees for PV systems, and which only credit homeowners for the wholesale price of electricity (say, 4 cents or 6 cents a kWh) instead of the retail price of electricity (say, 12 cents or 15 cents a kWh). If you life in a region with this type of utility, you may want to rethink your plan.
As a rule of thumb, the typical net-zero-energy house has a PV system rated at somewhere between 4 kW and 8 kW.
@ Martin,
Duhhhh... that should have been my first point of research. Also, as a former renewables energy guy, I know that what purchase tariff that exists today, may not exist tomorrow.
Thanks for the advice, a quick check shows that Georgia Power buys PV energy back at .17 a kwh, HOWEVER......they only buy so much per year, and all those spots are taken, but they will gladly put you on a "waiting list".
Thanks, since there is no obligation for any utility in my area to purchase the power, and I am not interested in "off-grid", back to the Gas water heater!
Georgia Power was fighting paying ANYTHING for small scale rooftop power going onto the grid, and had the 17 cents up to some xxx Mwh/year number by the Green Tea coalition of Tea Party and several environmental groups. They were also required to buy some amount of power from independent utility scale generators, and that ended up getting bid down to something like 6 cents/kwh (!), which means the big solar companies can still make money with 6 cent wholesale power at the current PV component prices and federal tax subsidies. But their cost in large scale arrays are lower by about half what you would be charged for a smaller rooftop array.
There is a good chance that more rooftop PV can be crammed down their throat, but Georgia Power is one of the tougher nuts to crack- a state wide vertically integrated monopoly with a lot of political power and a history of cozy relations with the regulators. They were even allowed to begin rate-basing the capital cost of the new nukes going in at Vogtle years ahead of even loading the fuel rods. Like many other nuclear power plants, the capital costs keep rising with every delay,and there have been several. If the full-cost of Vogtle gets rate-based, power may become expensive enough that it makes financial sense for those with access to the sun and capital to defect from the grid entirely, which would shove those costs onto the ratepayers of lesser solar & financial access. This oncoming storm has been brewing for awhile, but it's not even begun to rumble at full force yet.
For a spec house, the simplest metric to shoot for would be a HERS score of 0. While hitting this metric might have you installing a little bit more PV than a more energy conservative and/or smaller household needs on an annual basis, it's a lot easier to sell a HERS 0 house as "net zero" than something like a HERS 11 house as "net zero...as long as your family is not too big and doesn't use too much hot water and doesn't have 4 gaming systems, etc." I suspect folks don't want to hear "ifs and buts" during a sales pitch. Besides, if there is extra production, it will soon get taken up when the owners buy/lease an electric vehicle.
Finally, Georgia DOES still have standard net metering (in addition to the $0.17/kWh feed-in-tariff), so there's no reason to necessarily go to a gas water heater, as you mentioned. It looks like net-metered systems are limited to 10kW in GA, so if your goal is HERS 0, there's your PV "budget". Design a house that's efficient enough to achieve HERS 0 with a 10kW (or less) PV system.
@ John, I have looked up and down and it seems that that program of .17/kWh is fully subscribed and there is actually no program in place to take my PV power once I produce it. Since I wouldn't put PV in place unless I could "do something with it" I wonder if the paradigm of PV and a HP H2O heater is valid in georgia. In my mind this puts a "home grown" solar hot water system back on the table, even though Martin "proved" that it was not as economical as the former set-up.
I assume that the waiting list is very long and the contracts, when available only run for 5 years. Without wanting to put a DC system in place, my Solar Big Toe just froze solid.
So it's back to building a "pretty good house", and maybe with a Solar Hot Water Heater, maybe.
The grid-tied PV + storage game is just getting started in Australia, where the instantaneous power going onto the grid from grid-tied PV is compensated at 0-8 cents/kwh, and power being drawn FROM the grid is billed at 28-36 cents/kwh. Even with that imbalanced form of net-metering it's cost effective to put up smaller PV arrays, but now that SolarCity has a behind the meter battery solution that will prevent exporting to the grid whenever there is un-filled battery capacity, it will become commonplace. There is also going to be a substantial storage retrofit market for the million odd existing rooftop arrays in Australia. At the moment SolarCity is using Tesla car batteries for the PV storage systems, but as the giga-factory in Nevada comes on line they are talking about end-used tuned battery technology, producing a different battery for the storage market than for the car market. Already folks in Australia are hacking in tiny controllers to direct any excess power to a heating element in their hot water heaters rather than exporting it to the grid, only to have to draw from the grid later.
Australia is a good test market for storage, since rooftop PV systems are going up in Australia at 2.8 systems per minute, roughly the same rate as the US as a whole (!), albeit with smaller average array size, and the net-metering deal is as stingy as some of the worst US net-metering. As the technology matures a bit (give it 2 years) the costs will come down and any design/function problems will get ironed out. Eventually the lifecycle cost of PV + storage will hit grid-parity with expensive-electricity states (it's already cost-competitive in Hawaii) , and GA seems poised to become one of those expensive electricity markets when the full cost of the new Vogtle nukes get rate-based.
Some utilities are trying to stem the ratepayer-owned PV tide with "connection fees" or per-kw fees for PV owners, but for that will prove to be a short-term strategy at best. It doesn't take more than a few ratepayers defecting from the grid before that becomes a cascade of falling demand and lower revenues, and if they enhance the cost effectiveness of un-plugging from the grid by continuing to stick it to the PV owners, that WILL happen.