(Firstly I apologise for the length of this, but I wanted to explain the whole situation just so there’s no ambiguity).

Here in Brisbane, Australia we get 7-8 sun hours per day on average (source: http://www.livingin-australia.com/sunshine-hours-australia/ ); our household uses ~20kWh per day based on the average of all the power bills for 2009. Using this calculator ( http://www.bdbatteries.com/panelcalculator.php … too lazy to crunch the numbers myself) it tells me the ideal system is 3.2 kW. Our house has a large north-facing roof so that is good enough for solar panels. For practicality (and to keep the numbers conservative) I sourced the figures for a 3.5kW system which is within the price range of -40k, but after selling RECs (Renewable Energy Certificates) and taking advantage of federal and state subsidies and offsets it is priced at ~-20k; I’ll assume a worst case (say, k) to keep it conservative.

With a Home Equity Line of Credit Loan we currently have 0,000 in debt overall. At ~6.5% interest the monthly repayments are ~,190. If we were to throw the ,000 for the entire solar setup onto the loan, the loan would increase to 5,000 and interest would be ~,330 per month, a 0 increase. Since we are currently paying 6 per month (.20 per day) in power bills, it seems it is not worth it. However, 3.5kW x 7.5 avg sun hours gives 26.25kWh daily, or ~6.25kWh more than is needed. When taking into account the 44c/kWh feed-in tariff that is a lowest possible return of ~.50 per month (I say "lowest" because it is real-time net metering, so if we have nothing running during the day it will send a lot of power priced at 44c/kWh to the grid; when we buy it back when we are back from work at night it will cost only 16c/kWh, so overall we will gain more than .50 per month).

So then if we had to pay 0 extra per month on the loan but that eliminates 6 per month in power costs and includes .50 at the minimum in feed-in credits, is that is effectively a saving of .50? I know it isn’t really a saving per se since simply paying loan interest doesn’t reduce the loan’s size, but to me it seems to be a saving since the power cost of 6 per month will always be there so it may as well be moved from one account (elec) to another (HELOC loan) without making much difference financially; also the HELOC loan can be paid off and thus interest repayments become lower, while the cost of electricity is only set to rise (on top of inflation-adjustment each year, we are expecting sharp rise when the carbon trading scheme gets passed, and the generators were granted a 16% increase for January 2010 anyway!!!). Additionally when the 3 kids have moved out of home the power use will drop, leaving more electricity for the grid (so more money returns) in addition to less expenses overall (so the HELOC loan will be easier to pay off) – seems like a double win!

There are two major downsides that I can immediately see: variable interest rate rises and home valuation. However for the latter, I am not sure whether it is really a problem. For all I know, solar panels would most likely increase the value of one’s home (seems to be logical anyway), which in turn means more flexibility regarding the floor of the HELOC loan if it is needed.

I am somewhat naive regarding how HELOC works so that is my main concern in this plan. So is this too good to be true, or have I missed something (I generally don’t believe in "too good to be true" hence why I am asking).
Naive re HELOC; I am one of the 3 kids mentioned in the question (19yo) so this is just for me to propose to my parents as an idea.

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