Counting the Cost of Passive Solar Installations

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Most, if not all, proponents of solar energy will exhort the long-term value of installing passive (and active) solar systems. The return on investment over the life of the installation is always impressive on paper and professional installers will happily spend hours explaining how the cost works out as a tiny percentage of your income. Then they'll just as happily bill you five figures!

So what is the real cost of installing a passive solar setup and how does the return on investment really look in the short and long terms?

Passive solar in new builds

Almost every year, building codes change to include more demands for better energy efficiency in windows, floors, foundations and ceilings. While this makes builders' jobs more complicated, it's great news for the passive solar enthusiast as it means the majority of the changes they want to implement are already included in standard construction.

Research shows that including passive solar options increases the cost of a new build by between 0% and 3%. On a home costing $250,000 to build, that means at most $7,500 extra. That's quite a lot of money, but the returns on that extra investment can be astronomical.

The National Renewable Energy Lab and the American Solar Energy Society have actually conducted a survey of passive solar homes across the US, from different states experiencing different needs and climates. Their study found that the annual savings in heating these homes ranged from $200 to $2,255 in 2002.

Over a 30-year lifespan, that meant savings of between $6,000 and over $67,000. And that was with fuel prices much lower than they are now, more than ten years after the survey! If you take an average fuel cost rise of only 5% a year (which is very low) and recalculate, you're looking at savings of between $13,000 and $150,000 over that same 30-year period. If energy prices rise by an average of 10% per year, you could save the cost of building the entire house.

Passive solar as a retrofit

It's more difficult to calculate the financial benefits of a retrofit, as the costs tend to be higher. Existing work has to be undone or demolished before the new systems can be implemented and the building layout and design, local codes, zoning restrictions and other factors can affect how much energy you can save.

However, even if your passive solar installation reaches the $10,000 mark in construction costs and only puts your savings at the bottom end of the scale, you are still likely to recoup the cost in less than the 30-year period outlined above, especially with rising fuel costs.

The good news is that modern passive solar options can be integrated into almost any existing home design – even such traditional options as Victorian homes or log cabins!

Other benefits of passive solar

There are additional benefits that come with adding passive solar to your home. Property value and marketability are directly affected, especially as fuel costs continue to rise – a property which boasts significantly lower heating bills is far more attractive