What Might An Off-grid System Cost

This is a list of materials and a cost without installation for a 6.4 kWh panel system. This is provided for a guideline only, and each customer's needs are different and each house is a custom design.

This example package is for the following application:

• Insulated home or cottage used year round, power required 24/7 even when unoccupied
• There is sufficient space for a ground mounted array of solar panels facing south
• Prepared Dec 2020

It features:

• 6.4kWh of solar panels (16 x 400W)
• 733AH 48Volt flooded lead acid battery bank. 28.15kW energy storage to 80% discharge
• 4 day without sunshine power rating 7.03 kWh per day, 5 day rating 5.63 kWh per day, with discharge depth = 80%
• 120/240VAC so standard house wiring techniques can be used. See our off-grid FAQ page for more detail on this topic.
• Propane powered automatic start backup generator
• Code compliant design
• Can be expanded efficiently without wasting any components
• It is ready if in the future a grid connection becomes possible, it is ready for net metering, or just using the grid to replace the regular use of backup generator, and only using the generator for long duration hydro outages.
• All of the parts are made in either North America or Korea
• Ground mounted metal frame racking system.

In the above table the red font indicates items that we do not supply. The generator is nearly 400lbs and requires mounting on a prepared slab or paving stones. Since it is propane we suggest you buy this from a specialist in generators who is licensed to hook it up to your propane distribution system. You can then tie this into your off grid modules. The Thermocube is intended to turn on a battery warmer and carburetor preheat when the outside temperature falls below 0C.

The generator is an essential part of an off grid system. I don't recommend a DC output generator such as the Kohler 6VSG even though the output of 6kW is about right. The reason is the charge management system is very basic and is not flexible for anything except lead acid batteries. When the generator is running and the sun is shining the generator does not take into account the charge coming from the solar charge controller. As a result sometimes it may charge at too fast a rate. With an AC generator and the Outback charge controller and inverter/charger they are programmable to suit a number of different battery types, and coordinates the charging from both the generator and from the solar panels. Unfortunately the lowest output generator with 240VAC is a 14 kW unit which is bigger than required. However I selected it as is still a good choice for this application. Also an AC generator can run in pass through mode. In this mode and with the generator big enough to handles loads greater than the maximum inverter output the generator supplies the load directly. This allows for the short term use of heavy loads such as woodworking power tools, welders, etc. In addition an AC generator can power your house if an inverter fails in pass through mode until you can repair the inverter. With a DC generator you will be in the dark.

Battery technology: This Outback equipment can handle some types of 48V Lithium Ion batteries that emulate lead acid batteries. They specifically support batteries by SimpliPhi and Blue Ion. However the same amount of energy storage using Lithium batteries is about 3.6 times the cost of the flooded lead acid batteries I have selected. The Lithium Ion batteries can offer longer lifetimes of 10,000 cycles vs 2800 cycles for the flooded lead acid batteries included in this kit.

Flooded lead acid batteries have been the gold standard for off grid electricity storage since the advent of photovoltaic panels and are still the lowest cost, but highest maintenance type of battery for this service. There are a number of types of sealed lead acid batteries that are suitable for off grid use. The next most popular type of battery is the lead acid AGM, which cost more for the same capacity. The benefit to the homeowner is that they do not need water to be added periodically, and they are sealed so that no vent fan is required. These come at an increased cost of about $2510 before taxes for the kit. The reference AGM battery has a lifetime of 250 cycles discharged to 80%. The selected flooded lead acid battery is rated for 2800 cycles discharged to 80%. Therefore it costs less and has about 11 times the lifetime of an AGM battery. It is far better value for this application.

Rodent mesh screening. The wiring on the back of the solar panels requires protection from rodents and people's fingers. A fence around the panels is one method to keep people and animals away. Another is using a pole mount and mounting them high enough that no animals can reach them.

The ground mounted array is a metal frame attached to the ground at the front and back of each triangular leg. The legs are placed about 60" apart. This must be constructed to face due south. A top of pole mounting with 2 panels on top of each of 8 poles would cost exactly the same for the solar parts, but it would need 3" schedule 40 pipe sourced locally.

4kW System Example Comparison

The major cost increase is due to larger and higher capacity batteries. Next there is the cost of 6 extra panels. Lastly there is a 2nd charge controller. This uses ground mounting for the panels as it is lower cost than roof mounting and collects more electricity since it can point in the ideal direction.

AFCI and Rapid Shutdown code requirements

These two code requirements add about $3600 before taxes to the cost of the 6K system. These are not required for a ground mounted system, and so this system cost is lower than a comparable roof mounted system, even though the ground mounting racking is more expensive than roof mounted racking.

AFCI is an automatic type of circuit breaker that monitors the DC circuit and if an arc or spark occurs it opens the circuit to stop the arc. This is one method to reduce the possibility of a fault from starting a fire. It is required in Ontario for all DC circuits operating above 80V. It is not required for a ground mounted solar system.

Rapid Shutdown is an automatic or manual means of opening the DC solar circuit(s) so that a fire fighter can chop a home in a roof and not have the risk of cutting a live circuit. It can be instigated manually by a switch operated by the fire department, or operated automatically if the AC side of the system is shut down. The system in this list uses the manual switch method to command a shutdown. When an off grid system is not serviced by a fire department or the local fire department has a policy that they never chop holes in roofs to fight fires this provides no benefit to the owner of the off grid system, while it increases the cost and complexity of the system and decreases it's reliability. Currently the Ontario electrical code requires this feature for all solar PV systems even if they have no fire department service. This is not required for a ground mounted system.

In the case of our 6.4k system the entire parts cost is about $2100 less than a roof mounted version. This is if you pour concrete mounting posts or piers yourself. Then there are some benefits of a ground mounted system in the winter. The panels can have a greater tilt and they can safely have the snow raked off them to maintain wintertime production. And if your home or cottage does not have a roof facing due south, the ground mount will face due south improving the amount of electricity captured with the same number of panels. There is more detail about the benefits of ground mounting on the ground_mount page.