Considering life on the grid, off the grid, or somewhere in between? We address some basic concepts for off-grid living.
On-Grid or Off-Grid… What’s the Difference?
There are several flavors of “off-grid” power options. The default for most Americans is an on-grid system, which is dependent on electricity supplied by the utility company. A less common backup, familiar to those in rural (and especially hurricane-prone areas) is the use of a backup generator to provide short-term **backup power** during a power failure. Much attention has also been given to **grid-tied** solar systems, which allow the consumer to sell power back to the utility company. Finally, there is true **off-grid power**, in which the owner is responsible for every element of the system.
Being on-grid means total reliance on the power company to maintain infrastructure and reliably deliver power. In rural areas, or during storms and natural disasters, extended power outages are a reality that must be considered. A backup generator is a useful stopgap, but is dependant on how much fuel can be practically stored. In a long-term economic or societal collapse, this may not be sufficient.
Grid-tied systems have been touted for their ease of installation, cost savings, and environmental (and tax) benefits. Despite this, grid-tied systems often do not provide a benefit in self-sufficiency or survivability. A typical grid-tied system is designed primarily to feed energy back into the power grid, and cannot function to power a single residence on a regular basis. Without a battery bank and charge controller, these systems can only provide power while the sun is shining.
A full off-grid power system encompasses all aspects of a power supply, and the owner takes on the role of the utility company. It may be practical to also provide a grid connection, but an off-grid system is designed to function completely independently, providing all the ongoing energy needs of its owners.
Replacing the electric utility company requires taking on several roles: power generation, management, storage, and distribution.
How do I generate power off-grid?
Residential solar power is based on photovoltaic (PV) cells, commonly referred to as solar panels. The technology is becoming more and more cost effective, as the cost of photovoltaic panels continues to decrease. The decreased costs have made solar power attractive even at northern latitudes and in cold climates. Solar systems can be vulnerable to hail and snow.
Microhydro power takes advantage of natural water flow to generate electrical power by coupling a generator to a water wheel or turbine. The main determination is physical, as the energy must be extracted over a significant drop in elevation (head). In locations with a strong, year-round flow and suitable head, microhydro can provide a very reliable power source.
Wind power is generated by a wind turbine, which drives a generator. It is limited by prevailing winds, but is worth considering in areas with strong, steady winds. Wind systems are susceptible to storm damage, and require more hazardous work with mounting towers.
What’s a battery bank?
A battery bank is the critical component of any off-grid power system. Electricity can be generated in many ways–solar, wind, hydro, generator, even muscle power from a stationary bicycle! However, each of these sources may not deliver power at the time or rate that is required. For example, one would want to generate solar power during the day, and then run interior lights at night. In other circumstances, one may want to have a “bank” to draw on–if, for example, a sunny day is followed by a cloudy day where power generation is insufficient.
Battery banks are typically based around lead-acid batteries, similar to car batteries. Typical car batteries are not suitable, as they are not designed to provide steady power, or to be repeatedly drained and recharged. Instead, consider the use of “deep cycle” marine, forklift, or golf cart batteries. These batteries are designed to withstand many cycles of use, including complete discharge, while providing steady power output. Lead acid batteries do have a lifespan of approximately 10 years and do require periodic maintenance.
What’s an inverter or charge controller?
A charge controller is an important part of an off-grid system, which monitors and manages the charge in the battery bank, to best take advantage of power as it is generated, and to meet usage demands. A good charge controller ensures optimal efficiency for the system and the best performance and lifespan from the battery bank.
Photovoltaic panels and batteries generate a direct current output. This is not naturally suitable for residential use, where 120V AC is required for typical household appliances and electronics. An **inverter** is an important component, which converts the direct current from the battery bank or solar panels into a steady AC source to power consumer appliances. A pure sine wave inverter should be used, to provide a reliable power source for any sensitive electronics.
What is it like to live off-grid?
Generating your own power makes energy efficiency a must. An off-grid system can provide plenty of energy, but high consumption devices should be avoided, to keep the system economical. Most notably, look to reduce electricity usage on any devices with a resistive heating element. These devices can put the highest demands on a power system. Electric ovens, hot water heaters, space heaters, dryers, and incandescent light bulbs all have substantial power requirements.
Consider propane or wood for your cooking and heating. Unlike gasoline, propane has an effectively infinite shelf life. While still dependent on a long supply chain, it is possible to store propane for multiple years of use. In areas with sufficient timber, wood is an unlimited resource, limited only by your capacity to cut and haul.
Incandescent lighting can be replaced with LED or CFL bulbs, that produce equivalent light at a fraction of the energy usage. Many small appliances, even microwaves and hair dryers, can be used with an off-grid power system, if it is sized well.
How do I design an off-grid power system?
Design your system around minimum generation conditions–mid-winter for solar, low flow for hydro, and low wind speed for wind power. Size the system such that the total power output will meet your basic needs even in the worst conditions. Start by looking at your current electric bills, to gauge your actual usage. Then break down your energy budget by individual devices. A Kill-a-Watt power meter can be a useful tool for gauging actual loads from each device. Take note of the maximum load as well as average load.
Consider sizing a battery bank to cover worst-case needs. Heavy winter storms can majorly impact solar generation capacity, and the battery bank needs to be able to meet the shortfall or be supplemented with a gas or propane generator backup.
Self-Sufficiency and Responsibility
Living off grid means adapting a self-reliant mindset. It’s not a “set it and forget it” solution. In fact, it requires learning new skillsets as you take on the responsibilities that used to be invisible. Just like drilling your own well or growing your own food, generating your own power gives a greater appreciation for the work that countless individuals do to maintain our critical infrastructure.