Off or On Grid?
By: Ian Woofenden
HP Online
Dreaming of cutting the cord and getting rid of the big bad
utility? Perhaps you should think again. Renewable electricity has lots of
benefits, but stand-alone (off-grid) systems are more expensive and complex,
and require more maintenance than batteryless grid-tied systems. And there are
other big advantages to installing renewable energy systems on the grid. Before
you make your decision about whether to be off grid or not, let’s take a closer
look at the pros and cons.
System Types
Three basic categories of renewable electricity systems are
available today (though the future may hold more!).
Stand-alone off-grid systems are completely independent of
the utility grid. With the exception of direct-use systems like water pumping
or PV-powered ventilation, stand-alone RE systems must have batteries to
provide energy storage during times of low input or high usage.
Battery-based grid-tie systems are quite similar to
stand-alone systems. They also use batteries, but they are connected to the
utility grid, so they can send out to the grid any surplus electricity
generated by the RE system, and use utility electricity when needed.
Batteryless grid-tie systems are the simplest of all
systems, having only the energy generation technology (be it PV modules, or a
wind or microhydro turbine) and an inverter connected to the utility grid. They
do not have batteries, which points to their primary drawback—they have no
backup capability. When the grid goes down, these systems also shut down.
Off-Grid Advantages
Independence
is chief among the reasons for wanting an off-grid system where the grid is
available. Off-grid systems are not subject to the terms or policies of the
local utility, nor are system owners subjected to rate increases, blackouts, or
brownouts.
If you’re shopping for rural property, you’ll probably find
that off-grid parcels are less expensive. Most people aren’t ready to take on
being their own utility, and the land is priced according to this value system.
Being off-grid can also be cheaper than getting a utility line extended to a
property. But bear in mind that with off-grid renewable electricity systems,
there are up-front and ongoing costs.
Off-grid systems may have a slight edge over grid-tied
systems when it comes to expandability. While both are modular, it’s often
easier to grow an off-grid system as you can afford it. In fact, many
off-gridders with limited incomes find this to be the norm—gradual weaning from
fossil-fueled generators by adding more renewable capacity. With lower array
voltages (12 to 72 VDC nominal), one to four modules can be added at a time.
Batteryless grid-tie systems run in the 150 to 600 VDC range, and specific
inverters have voltage windows and efficiency curves, so that adding to them
requires more modules and, possibly, another inverter.
Unless you can afford an oversized system, off-grid systems
tend to force you to use electricity efficiently. This is a big advantage if
you also hold environmental values. Some of the most energy-efficient homes in
the country belong to off-grid folks. When you have to make all your energy
with only the available resources at your site, you think about how to use that
energy wisely.
There are many less tangible advantages of being off grid as
well, including the satisfaction and peace of mind that goes with using
electricity responsibly. And maybe your neighbors will begin to think you are
way ahead of your time.
Off-Grid Disadvantages
When you make the decision to go off grid, you take on the
duties of the cursed utility you were trying to avoid. My experience is that
you tend to curse them less and appreciate them more as you tackle these responsibilities.
First and foremost, making all of your own electricity is
costly. If you are already on the grid, it’s unlikely that installing an
off-grid RE system will provide you with cheaper electricity, unless your area
has generous incentives, very high utility rates, or both. (Note that most
financial incentive programs apply to on-grid systems and do not apply to
batteries.) Of course, if you’re a long-term thinker, this changes the picture.
But most people conclude that “going off grid” to save money is not a winning
concept. With existing off-grid property, you need to weigh the cost of line
extension against installing an off-grid RE system. In some areas, utility line
extension can exceed $20 per running foot.
System maintenance and troubleshooting are serious, ongoing
responsibilities with off-grid systems. When you pay your utility bill, you’re
paying for those hard workers in business suits and coveralls to take care of
things. If you are the utility, you have to do the work all by yourself, plus
buy the coveralls.
Off-grid systems use batteries to store electricity and
provide it for your home, but batteries don’t last forever. In fact, they will
need replacement every five to fifteen years (typically less than ten, unless
you have deep pockets for high-quality, industrial-type batteries). A minimal
bank of batteries will cost at least $1,000, and long-lasting industrial
batteries for the same application might cost three to four times that much.
And it’s not just the cost in dollars that’s a disadvantage. There’s
maintenance and replacement time, aching backs from lifting that heavy metal,
and perhaps labor cost—and then there’s the environmental cost of making,
moving, recycling, and replacing all that lead.
Batteries have another, less tangible cost, and that’s
energy waste. At their best, batteries are 90% efficient. That means if you put
in 10 kilowatt-hours (kWh), you will get out less than 9 kWh. As they age,
their efficiency drops further, and they are also affected by temperature. All
this adds up to more energy waste the larger, older, hotter, or colder your
battery bank is.
In comparison to grid-tied systems, stand-alone systems have
another serious drawback—wasted surplus energy. When a grid-tied renewable
electricity system makes more than the homeowners use, the surplus is fed to
the utility, creating an energy credit and allowing the system to always run at
full capacity. Nothing is wasted, and the grid is figuratively (not literally)
100% efficient—you get credited for all that you throw their way. When you’re
off grid, your surplus must be used or it will be wasted. With most off-grid PV
systems, the array simply gets turned off by the controller when the batteries
are full, so the energy is never generated. With most wind and hydro systems,
the excess energy is shunted to a dump load, typically an air- or water-heating
element. Savvy off-gridders are aware of their system operation, and change
their energy-use habits when there’s a surplus—like choosing to do laundry in
the middle of the day. But it’s not automatic, and it takes some social
adjustments to switch from energy sipper to energy gorger depending on the
weather.
Most off-grid systems need a backup engine-generator, and
this is another big disadvantage of these systems. Generator electricity is
expensive when you calculate the cost of purchasing, fueling, and maintaining
these dirty, noisy machines. And if you buy a cheap model, you might end up
with what veteran off-gridder and RE installer Roy Butler calls an “800-hour throwaway”
and have to replace it sooner than you wished.
If living off grid sounds like a bit more trouble than you
expected, good! I’d like you to be successful with your renewable energy plans,
and being realistic is a good first step. My family moved off grid in 1981, and
my wife and I have raised a raft of kids and run several businesses from home,
so I know that it’s not always a picnic. We’ve been through multiple
generators, and have had hard times when we had to wait for the weather to
change before doing the laundry. The social and familial implications of living
with a variable energy source shouldn’t be underestimated!
Living off-grid can be satisfying, but it’s also a big
responsibility. It’s necessary to be willing to flex your electrical activities
with the changes in the weather, or be willing to start up a fossil-fueled
generator whenever nature is not cooperating with your energy plans. If you’re
a city dweller who gets impatient when the traffic light takes a while to
change, imagine how you’ll handle waiting for the sun to come out or for that
mechanic to fix your generator.
On-Grid Advantages
Using renewable energy on the grid avoids most, if not all,
of the disadvantages of being off grid. The utility is like a big, 100%
efficient battery that can absorb all your surplus energy. In addition, you can
lean on it as hard as you want to for as much additional electricity as you
might need. If you can’t afford a renewable-electric system large enough to
supply all your needs, you can install whatever portion you can afford. If
you’re off grid, you have to make it all, one way or another, and if you’re
strapped for cash when you’re putting in your system, you’ll end up making a
lot of it with fossil fuels. When the grid uses fossil fuels, at least it uses
them more efficiently, and with less noise and pollution than a home generator.
With grid-tied renewable energy systems, there is no
absolute need to conserve electricity or change your lifestyle. You can choose
to live the same way you lived before you installed an RE system. Your system
will offset some or all of your usage, and your daily life can continue
unchanged.
If you decide on a grid-tied system with battery backup, you
can have the best (and some of the worst) of both worlds: You can have the
independence and backup of a stand-alone system, still be able to use at least
some energy during utility outages, and have the ability to sell your excess
energy to the grid.
For all these system types, investing in a PV system also
means locking in the long-term pricing of your electricity. With a photovoltaic
system, you are buying 40 to 50 years of electricity at a fixed price, while
maintaining the benefits of being on grid.
On-Grid Disadvantages
One major disadvantage of having a grid-tied system is that
you have less incentive to conserve. That inviting wall receptacle will take
whatever you plug into it, and no “depleted battery” warning will sound when
you use a lot of electricity. If you can manage to bring an off-grid mind-set
to your on-grid home, you’ll make the most of your RE investment.
With batteryless systems, you’ll have no backup. In most
cases, this is not a very serious drawback. The utility grid is quite reliable
in most urban places in the United
States, with outages occurring only a few
times a year for a few minutes to a few hours. But if you have frequent or long
outages or critical loads, a batteryless system will frustrate you and maybe
even cost you an occasional freezer full of food.
However, battery-based grid-tie systems typically only
provide modest backup. To power all of your loads during an extended outage
when there’s no sun would require a very large battery bank, which would be
expensive and make for a less efficient renewable energy system.
For all grid-tied systems, you also have interconnection red
tape. This can range from simple to onerous, depending on the authorities and
utility you have to deal with. In places where RE systems are becoming common,
there may be a greased path through your inspection agencies and utility, once
you know the right people to deal with and the right forms and procedures. If
you’re pioneering a new path, you might run into a lot of roadblocks, such as
public servants or utility personnel who are ignorant of these systems, or
burdensome gear or paperwork requirements.
Weighing the Costs
So how do you make the choice between being on grid and off
grid? This is a personal decision, based on finances and personal values.
First, weigh the costs. A battery-based system generally costs about 30% to 40%
more than a batteryless grid-tie system, and maybe as much as 50% more,
depending on the battery bank size and other components. The other major
consideration is the cost of utility-line extension. This can range from zero
for properties close to existing utility lines to hundreds of thousands of
dollars for properties that sit a long way from the line. Get quotes from solar
contractors and from your utility, and then crunch the numbers.
Values are a bit harder to evaluate objectively. I know
people who were faced with $25,000 line extension costs to get utility
electricity to their property. They opted to stay off grid and, in the end,
invested more than $75,000 in their wind- and solar-electric systems. For this,
they get satisfaction, independence, and no utility bills. Obviously, the
up-front cost was not their highest consideration—they have other values. But
they invested a lot of money and time initially, and will have the continued
investments in time and money to keep their systems running. Others may decide
to spend anywhere from a few thousand to tens of thousands of dollars for the
reliability, efficiency, and convenience of having the grid, even if they
invest in an RE system that will offset all of their usage and bills.
From the perspective of more than 25 years of off-grid
living, my advice is not to unplug from the grid if it’s there. Of course,
there are exceptions to every bit of advice, and if you live where net metering
(selling back to the grid for credit) is not available or monthly base charges
are high, you have a different situation. But in general, “greening up” the
grid with your renewable electricity will benefit you, the environment, and
your community better than cutting the cord.
Access
Ian Woofenden has lived off grid with his family in Washington’s San Juan Islands
for more than 25 years.
