I had a phone call from a mate today asking for advice on buying an off grid solar system for his new house in suburban Melbourne. He was pissed off about paying the daily grid connection charge when his solar system was easily going to produce more power than he used. A typical grid connection charge is about 50c per day.
So what is the extra cost of getting completely off the grid with your solar system in the city compared to a standard grid connect solar system?
Let’s take a 5kW system that would power an mid sized air conditioned house as an example.
On Grid Cost:
5kW of panels $7,000
5kW inverter $3,000
Racking and Cabling: $1000
Less Solar Rebate (STCs): -$,3500
Out of pocket cost to you approx: $9,500 (Jan 2013 prices)
Off Grid Cost:
5kW of panels: $7,000
5kW Off Grid Capable Inverter: $5,000
4 x 1350 Ampere hour 12V batteries: $18,000 (approx 50kWh of storage)
Racking and Cabling (you’ve gotta wire up and mount all those batteries remember!): $3,000
Installation and commissioning: $4,000
Integrated Diesel Generator (unless you don’t mind running out of electricity occasionally): $5,000
Less Solar Rebate (STCs): -$,3,500
Total Cost of Off Grid Solar System: $38,500 ($29,000 more than the grid connect solar system)
So if my mate is going to go completely
off his head off the grid, he is going to save 50c per day, or $180 per year.
But he is going to be paying $29,000 more for the privilege. That makes the payback for going off grid…. wait for it… 160 years!
My advice to my buddy: Get a grid connect solar system.
Please Note: These costs are for going completely off the grid for a typical Aussie home in the city. You can pay a lot less if you have a very energy efficient home and – but let’s be honest – most people don’t!
There is also a compromise solution and that is to connect your solar system to the grid, but still have a battery backup. This type of solar system configuration is a lot less expensive than the system described above, because you don’t need the generator or such a fancy inverter, or nearly as many batteries. This kind of hybrid arrangement is also sometimes called “grid-tie with power backup”, “grid failover” or “grid fallback”. I’ll run through the design and costings for these kinds of systems in a future blog post.