Choosing Between a Grid-Connected and Off-Grid Array
A grid-tied system is connected to the utility and is usually the cheaper, simpler choice. An off-grid system runs independently with batteries, costs more for the same panels, and is usually chosen only where the grid is far away.
What is the basic difference?
Both use panels and an inverter. The grid-tied version sends surplus power to the utility and pulls power from it when the sun is down. The grid works as the battery, the backup and the voltage reference. An off-grid version has none of that, so it must store energy and supply its own stable power every second of the day.
Between them sits a hybrid: grid-connected with a battery, which can ride through outages. See solar batteries for what that adds.
How do costs compare?
Grid-tied systems avoid large battery banks and generators, so they cost less per kilowatt of panel and give the best chance of paying back. Off-grid systems add storage, bigger inverters, backup fuel and design margin. For a grid-tied cost outline see the solar cost guide; for off-grid sizing, off-grid solar in Canada.
A quick illustration with assumed numbers: if a utility connection is available, the choice is between a modest grid-tied system and an off-grid one that must be oversized by perhaps a factor of two or more to cover winter and inverter losses. Where a utility line extension would cost a very large sum, the comparison can swing the other way. Only a quote for each tells you.
How does reliability compare?
Grid power is typically more reliable than any single home system, and a grid-tied house can lean on it day and night. The exception is an outage, where a basic grid-tied system shuts off with the grid. Read why panels go dark in a blackout before assuming otherwise.
An off-grid home keeps working in a grid outage but depends on the owner's equipment, maintenance and fuel supply. A failed inverter or an empty battery in January is your problem alone, so owners typically carry spares and a generator.
Households sometimes ask whether going off-grid saves the monthly fixed charges on a utility bill. It can, but the comparison should include replacing the batteries every so often and the fuel and servicing for a generator. Add those to the capital cost and the annual figure usually exceeds the fixed charges by a wide margin. Cases where it does not are mostly sites with no service available at a sensible price.
What do the rules and credits look like?
Grid-tied systems need an interconnection agreement with the utility and often a permit and inspection. Many provinces have a billing arrangement for exported power. In Alberta, the framework is described in Alberta net metering, and the terms of such programs change, so check with the provincial energy ministry and your local utility for current rules.
Off-grid systems skip interconnection but still need electrical permits and inspection in most places.
How to decide
If you can connect to the grid at a reasonable cost, a grid-tied system is generally the economic choice, with a battery added only if outages matter to you. If the nearest line is far, a utility estimate for extending service is the figure to compare with an off-grid quote. Heat is a separate question: much of a Canadian home's energy goes into space heating, where options such as those in solar space heating or a heat pump may do more than extra electric panels. The Drake Landing community, an example in how it worked, stayed grid-connected for electricity and focused its solar on heat.
Whichever route you take, ask for the design assumptions in writing: expected annual production, the battery size if any, and the loads the system is meant to carry. Vague quotes hide the differences between these options, while a written design lets you compare like with like and gives you something to hold the installer to later.
Quick answers
Is grid-tied solar worth it if it shuts off in a blackout?
Yes for most households, since the value comes from everyday bill savings. If blackouts are a big concern, add a battery with backup capability.
Can I go off-grid later if I start grid-tied?
In principle, but the system would need a much larger battery bank and likely a new inverter. It is easier to plan for it from the start if independence is your goal.
Which is cheaper to maintain?
Grid-tied systems have fewer parts to maintain. Off-grid systems add batteries, charge controllers and a generator, all of which need regular attention and eventual replacement.
Do I get paid for extra solar power on a grid-tied system?
It depends on the province and utility. Some credit exports against your bill and some pay a set rate, so check current terms with your utility.