Should I take the loan with the dealer fee or a separate loan?

The "dealer fee" (sometimes called a "buydown" or "origination") is a percentage added to the cash price of the system so the installer can offer a lower advertised interest rate. It can be 15–30% of the system price on longer/lower-rate loans. It is real money you pay, financed over the loan term. Before signing, ask the installer for the **cash price** and the **loan cash price** as two separate numbers. Then get a quote from your bank or credit union for a home-equity loan or personal loan at the cash price. Compare total cost over the same term. In many cases, a slightly higher rate on the cash price beats a "low rate" on a marked-up price.