Inexpensive and Simple

When many of us hear the term ‘off-grid’ in terms of our homes, it’s easy to think it must be difficult or costly to get a off-grid, however it is actually very easy to implement and not terribly expensive. When viewed in line with typical utility bills, it simply makes sense.

A typical off-grid system might range from $20-$30k to purchase, which is a significant upfront investment for most of us, but seen over the duration of a mortgage, it would actually translate into a very manageable monthly payment, e.g. $170 / per month. This is actually more affordable than many typical monthly utility bills for homeowners.

All change…or at least, a significant shift

At this point in time, almost every off-grid project requires a generator, because the sun is not always shining and the wind is not always blowing, and the capacity for storing the energy generated by these sources in batteries simply hasn’t developed sufficiently.

The problem with conventional off-grid systems is that they require propane or gas, which are petroleum based fuels. As we all know, this represents a simply unsustainable energy supply. Which is why we turn to biofuel.

Why not use readily available bio-fuel?

We recommend using a generator that can burn vegetable oil or bio diesel.  These are the fuels of the future as they are non-petroleum based and renewable.

A European company, Gelec Energy, has a great selection of generators, including ones engineered for use with vegetable oil/biofuel.

With this technology, no one is reinventing the wheel; they are simply making use of existing diesel technology developed over 100 years ago. After all, deeply concerned about the pollution that accompanied the age in which he lived, Rudolph Diesel originally designed his engine so that it could run off peanut oil…

As a fuel, bio diesel is also reasonably affordable, costing as little as $.60 per litre, compared to much closer to a dollar per litre for gas at the pump.

What this looks like

In the summer period (mid-March to mid-October) an off-grid house is designed to run off solar PV panels and batteries. In the winter period (mid-October to mid-March) it’s engineered to run off a combination of solar PV, batteries, and the generator.

On average, a full-size family home will use 24 kWh per day in the warmer months, and 30 kWh per day in the cold season. The house can run directly off solar PV when the sun is shining, but here are the factors to consider for overcast days:

• Battery storage is 15 kWh.
• Batteries experience on average .5 charge cycles per day during the summer period and one charge cycle per day during the winter period.
• Batteries cost $15,000 and are guaranteed for 3,000 charge cycles which equates to a battery lifetime of 12 years. This averages out to $1,250 per year.
• Generator cost is $15,000; with limited run time it should last approximately 30 years, resulting in an annual cost of $625.
• On average, the generator needs to produce 15 kWh per day during winter. The generator can do this with 1.5 L used vegetable oil or biodiesel: 1.5 L x 150 days = 225L x $0.60 per litre = $135/year.

Total annual costs

• Cost for bio diesel approximately $0.60 per litre = $135 per year
• Generator cost amortized over 30 years = $625 per year
• 6 kW solar array and inverter $15,000 to last 50 years or more = $300 per year
• Batteries amortized over 12 years = $1,250 per year

Total = $2,310 per year. We conservatively estimate that this is 50% less than what most full-size family homes cost to keep heated and cooled when connected to the grid.

Interested to know more?

We’re happy to answer questions about how to take your home off-grid, particularly if you’re building new and want to know the best decisions to make upfront to maximize energy saving potential. Give us a shout today.

Related reading:

Going Solar: the EkoModel Home
Your House Needs a Solar Engine, and We’ve Got It