In a word: yes. It cost us $9K (or $6K out of pocket after taking into account the builder's allowance for insulation). We have only 3000 sq ft, but everything is electric except the stove top and the tankless water heater, and our electric bill has not topped $125 since we moved in. We did all the exterior walls and the roof decking. We have OC foam, full exterior wall OSB sheathing, and Tyvek.

From a financial standpoint I don't think it's worth it. It will take many, many years for you to get your money back. For my 2600 square feet house I calculated the payback is 20 years - so it's not worth the investment. Also, I don't think you would get your money back if you were to sell your house, since buying a house has an emotional element and people don't usually pay a premium for things they cannot see.

Too little information to give you useful advice.

Where is the project located, what R value is desired, what is the depth of the exterior wall studs, what kind of foam is being offered (open or closed cell), what is the R value per inch, and what is the exterior sheathing/air barrier/cladding/etc.?

You need to design the whole wall system rather than one element at a time.

is it worth it?

That's really two questions.

First, is this quote competitive with other spray operators in your area?

Secondly, what is the payback period vs. alternatives?

In Canadian Zone B (equivalent to US Dept. of Energy Zone 5 US) I've found alternatives that exceed Code and provide better value with our average home ownership period of 4 years before moving on.

In most cases, using spray foam will be a waste of money when you look at it from a return-on-investment point of view.

Foams can cost 5X more than more conventional methods while providing no added benefit.

Foams will therefore take up to 5X longer to simply pay for themselves before a penny is even seen on energy cost savings.

It's your money, but foams rarely ever pay for themselves in any climate.

Consider building your exterior walls (and roof if feasible) with SIP panels. Has the foam built right in, plus will give you a deep-set window profile, tight building envelope and some additional fire resistance if you use polyurethane SIPs. SIPs also add structural rigidity to the house - added benefit. If it's a house you're living in for the rest of your life, I think it's money well spent.

srg215, such a simple question with no specifics will not get you the answer you are looking for.

Tell us what you're trying to accomplish and where.

I would spray the attic as well, not much sense spraying the 4 walls and not the attic. Works best as an envelope!