Solar Power Revisited – We Are Carbon Positive

At the start of this year I decided to install solar panels on my roof.

I posted about how I arrived at the decision HERE

Now I have around 6 months data, and the Feed In Rate (FIR) has increased I thought I would check on how well the investment is going.

Power Use

Currently we use electricity for lighting, space heating, cooling, some cooking and general domestic use.

Between our 3.3kw of panels being switched on in late January and the 15th July the following data has been recorded.

• Power generated by panels:   1,801 kwhrs
• Power fed into grid:  1,389 kwhrs
• Power from grid:  1,158 kwhrs

As you can see I have actually put 231 kw hrs more into the grid than I have taken out.

In a full year I should be putting around 460kw hrs more into the grid than I take out, so we are now ‘Carbon Positive’ in relation to electricity use.

Cost Benefit

To calculate typical ongoing annual savings I have based all rates on the latest rates from our supplier Powershop (From 1st July)

• Grid Power cost   \$0.271
• Feed In Tariff   \$0.118

Annual Grid Power Costs Saving = (1,801 – 1,389) x 2 x \$0.271  = \$223.30

Annual income from FIT = 1,389 x 2 x 0.118 = \$327.80

Total Annual Benefit  = \$223 + \$327 = \$550

Annual Return on our \$4,450 system = 12%     (Around 4 times better than we could get at the bank)

Edit

After a years operation I find that the actual amount generated has been 4,310kwhrs an additional 509kwhrs over my original estimated annual output.

As we were overseas for the three months of winter I don’t have a realistic figure for what a typical usage would be so I am assuming that the all the additional power would go to Feed in Tariff (FIT)

This would make the revised calculations:

Annual Grid Power Costs Saving = (1,801 – 1,389) x 2 x \$0.271  = \$223.30

Annual income from FIT = 3486 x 0.118 = \$411.34

Total Annual Benefit  = \$223 + \$411 = \$634

Annual Return on our \$4,450 system = 14%     (More than 4 times better than we could get at the bank)