Tied to the Grid
 

Off or On the Grid

Courtesy of ReVision Energy Maine/New Hampshire

Off-Grid Vs. Grid-Tied Solar

 Many people say they want to get “off the grid,” when in reality what they mean is they want to reduce their energy use and offset what they do use with sustainable sources. Grid-tied renewable energy will last years with little (for solar) and regular (for wind) maintenance. True “off-grid” systems require batteries, which unfortunately are messy and not environmentally friendly. Typically used are lead acid batteries (similar to what are used in forklifts) which require diligent maintenance, and only last around 10 years.

Solar When the Grid Goes Out

The Case Against Batteries

No one’s happy when the grid goes out. Power outages are at the minimum inconvenient, and, if a home is poorly suited to be without power, problematic or even dangerous. So it would seem obvious, why not install a grid-tied solar electric system and power your home using sunshine during an outage? While technically this is possible, it is not so simple. When the grid goes down, the system goes down, too. This is by design: by shutting down, the grid-tied solar electric inverter (the component that converts direct-current power from the solar panels into grid-compliant 120V AC power used in your home or business) prevents power from back-feeding to the grid and injuring nearby line workers. The only way to circumvent this is to add batteries, which provide a backup source of power when the power goes out. Unfortunately, batteries are almost the antithesis of a grid-tied system: they are bulky, inefficient, ecologically unfriendly, unreliable and expensive.

Grid-Tied with Battery Backup Vs. Off-Grid

A grid-tied battery backup system uses the same principles as an off-grid solar or wind electric system when the grid goes down. Instead of shutting off completely, the system switches to an alternate inverter, which is designed to interact with a battery bank, letting you run household loads off the battery bank and charge them with your solar panels or wind turbine. The equipment to do this is quite sophisticated and is derived from R&D for very remote locations where grid access is not feasible. While they can work smoothly, they come at a great cost, especially once you consider the cost of short-lived lead acid batteries (using similar technology as is in your car battery). An average home with an electric bill of $100/month, for instance, consumes ~625kWh of power a month (assuming a grid price of .16c/kWh). That averages around 20kWh/day of power. Enough good-quality batteries to carry that load for just two days would cost around $25,000. Realistically, a battery-backup system is only designed to support emergency loads for short periods of time (water pump, refrigerator and maybe a freezer), but even so, the cost reaches approximately $20,000 of additional cost for a short-term grid-tied battery backup solution. Further limitations of this system is the battery life – approximately 5-7 years – as well as the battery potential. While this system can provide backup power for a few days, for true energy security you need an option for charging the batteries should a long-term outage occur during bad solar weather. So, even with a large battery investment you still require a generator to be totally secure. Getting To Your Goals: Why Are You Going PV? Most people look at a solar and wind energy investment as a way to reduce their fossil fuel energy consumption while locking in their electric rate below the grid average for a duration of 25+ years. Cost pressure on solar panels/wind turbines and generous state and federal rebates make grid-tied RE an excellent investment right now. Adding battery backup changes this equation completely. Dollars that could be invested in more renewable energy production are invested in short-lived, ecologically unfriendly battery components. Realistically, with the grid down as infrequently as it is, a battery backup system means you are paying a stiff premium for a system you do not need 99% of the time. With that caveat, there are times when solar or wind generators with battery backup meets specific goals, mostly in situations where no grid downtime is tolerable. For example, keeping critical loads like life support equipment, computer and communications transmitting equipment online, or simply ensuring fail-safe electricity for homes where one spouse travels frequently in the winter and doesn’t want their partner home alone in a power outage!

So What Am I To Do During Power Outages?

Though we are loathe to recommend the installation of a fossil-fuel burning appliance, the reality is that for the average numbers of days a typical home is without power (1-2 days a year or less), and given the cost and complexity of installing a grid-tied system with batteries, a generator is often a better investment. Even an extremely robust home standby generator is roughly 1/4 of the price of enough batteries and equipment to maintain a home for a few days without power. While a battery bank will struggle to keep up with heavy energy hogs like a refrigerator or well pump, a properly sized generator will carry these without missing a beat. If you just can’t stand the thought of a generator, here are some other power outage tips from our renewable energy experts:

  • Wood is good – Cord wood stoves are a tradition in New England and a wonderful appliance to have when the power goes out. They can be good for cooking and eating.
  • Stockpile water – Most people’s top complaint about power outages is running out of water. Fill up your tubs and empty milk jugs with water so you can cook dinner, wash hands and flush toilets during outages. And if you’re on city water and have a solar hot water system, you can continue to use your solar hot water even without power!
  • Keep alternative lights handy – With the sun firmly set by 5pm during the winter, a power outage can make for a long dark night. Luckily, LED flashlights are light years more efficient than their incandescent predecessors.
  • Make it fun – A power outage need only be as much an ordeal as you make it. Kids especially can be encouraged to make it an opportunity for adventure and find it fun to cook on the wood stove or propane grill. A bit of flexibility and patience go a long way.

Why Grid-Tied Solar Power is Better than Off-Grid for Most Applications

There is a common misconception that being “off the grid” is the ultimate goal is sustainability and that off-grid homes are, by their nature, greener and more energy efficient than conventional “on the grid” homes. Many people say they want to get “off the grid,” when really what they mean is that they want to reduce their energy usage and switch to renewable forms of energy. The good news – you don’t have to be “off the grid” to enjoy the benefits of renewable energy! In fact, your conventional home or facility is only a few smart steps away from dramatically shrinking its carbon footprint. We’ll talk about this in a moment – first, let’s demystify “off the grid” versus “grid-tied.”

What Does Off-Grid Really Mean?

“Off-grid” just means a residential or commercial building that is not connected to the utility grid. While these facilities are often designed to be more energy-efficient and sustainable than conventional designs, there is no requirement in the term “off grid” that makes them so. In fact, a building that is “off grid” can be just as much of a power hog as a regular building, and use a gasoline-powered generator for all of their electric needs. Hardly green OR renewable! The reality is that power generated off the grid is significantly more expensive, kWh to kWh, as power generated while tied to the grid. The grid has numerous efficiencies of scale – from generation to transmission – that isn’t achieved in an off-grid set-up. Because electricity generated off the grid is so expensive, it only makes sense that these buildings should use less power. It’s pure economics!

So Why Would Anyone Go Off-Grid in the First Place?

When people think of “off-grid,” they probably think of images from the early days of solar power, when people were moving far out in the country to get back to the land and live a more sustainable existence. Of course, moving far away from civilization brings its own share of challenges and environmental implications. Unless you’re planning to become a hermit, you still are going to need roads to get to your off-grid home, and won’t you want some sort of electricity? Creating power lines is expensive and destructive. It can cost tens of thousands of dollars per mile to run power lines to a distant homestead. In these situations, where connecting to the utility grid will easily outweigh the costs of a clean, renewable energy system, being off the grid can make economic and environmental sense.

Most People Don’t Live Far From Power Lines

Most people live near other people, which means that most people don’t need the hassles and expense of an off-grid renewable energy system. Instead, we can install a solar or wind energy system that interacts with the grid – offsetting your building’s energy use and providing surplus power to your neighbors. In effect, we are becoming our own miniature power plant! This kind of system is called Grid Tied Renewable Energy.

What Makes Grid-Tied Different than Off-grid?

Grid-tied solar or wind electricity is a much simpler set-up than off grid. In both cases, you have photovoltaic (PV) panels or wind turbines which generate clean, renewable energy. However, in a grid-tied set-up this power goes straight to your utility meter while in an off-grid set-up there are a few more steps. With a grid-tied system, any excess power generated from the solar panels goes back into the grid – helping your neighbors reduce their carbon footprint! In essence, you are treating the grid as if it was one big battery, charging it when you have excess power, and taking energy when you need more. With an off-grid setup, you also need somewhere to store your solar energy.  Without the grid nearby, you need to buy a large set of batteries. Unfortunately, battery technology is not as clean and renewable as the electricity generated by the solar panels or wind turbines. The batteries used in most off-grid installations are lead acid batteries – similar to what starts your car and powers forklifts. As you probably know from the explosion warning stickers on your car battery, the inside of these types of batteries are extremely toxic, and their production is an energy intensive and environmentally harmful process. While those in an off-grid set-up are stuck using this non green technology, if we have access to the energy grid we can avoid this messy problem and appreciate more reliable service with a grid-tied set-up. Not to mention – batteries are expensive!  The battery bank significantly adds to the cost of an off-grid solar system or wind turbine. In terms of cost per installed watt, off-grid usually ranges 3-4x the cost of grid-tied solar or wind energy.

Fossil Fuels are Bad, Not the Grid Itself

While it may seem romantic to be “off-grid” and not beholden to the utility companies, the reality is that most homes are connected to the grid already, and the efficiencies of the grid generally outweigh the independence of an off grid system. The grid itself is not inherently bad – what is bad are the forms of electricity that powers most of the grid. The way to make real, tangible improvement in the way we consume energy is not to distance ourselves from the grid, but to ensure that the power we consume is generated by clean, renewable solar or wind electricity at home and at our place of work.