What is a good APR for Solar Panel loans?

My electricity provider says that these are some of the options for Solar Panel loans.

3.9 percent APR for 24 months
4.9 percent APR for 36 months
6.9 percent APR for 48 months
7.9 percent APR for 60 months

I don't know a lot about this type of thing, but I thought that there is a usually a lower APR for longer term loans so that they end up making you pay more interest over the lifetime of the loan and they encourage you to do so by making the rate a bit lower.

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