The Amortization Formula
RV loans use simple-interest amortization, the same method used by auto loans and mortgages. Your monthly payment is calculated with this formula:
Payment = P × r / (1 − (1 + r)^−n)
Where:
- P = the amount financed (principal)
- r = the monthly interest rate (annual APR ÷ 12)
- n = the total number of monthly payments
The formula produces a fixed payment that, repeated over n months, will pay off the entire balance plus all interest owed.
Why Early Payments Are Mostly Interest
Even though your payment stays the same every month, the split between principal and interest shifts dramatically over the life of the loan.
In the first months, you owe interest on the full balance. As you pay down principal, the interest portion shrinks and more of each payment goes toward the balance. This is why the first few years of a long RV loan feel like you’re barely making progress, because most of your payment is covering interest.
Example: On a $50,000 loan at 7% APR for 180 months, your fixed payment is about $449. In month 1, roughly $292 goes to interest and only $157 to principal. By month 90 (halfway), about $186 goes to interest and $263 to principal. By the final months, nearly the entire payment is principal.
Daily Simple Interest vs. Fixed Amortization
Most RV loans are daily simple interest loans. That means interest accrues on your outstanding balance every day, not just once a month. Your scheduled payment amount is fixed, but the interest/principal split within each payment depends on how many days have passed since your last payment.
This has practical consequences:
- Pay late and more days of interest accrue before your payment is applied. A larger share of that payment goes to interest, and less to principal. Over time, this slows your payoff.
- Pay early (even by a few days) and fewer days of interest accrue. More of your payment goes to principal, which reduces the balance faster.
- Make extra payments and the principal drops, which reduces the daily interest charge going forward. Even small extra payments early in the loan have an outsized effect because they reduce the balance during the years when interest costs the most.
This is different from a precomputed interest loan (where the total interest is fixed upfront regardless of payment timing). On a simple-interest RV loan, your behavior directly affects how much interest you pay over the life of the loan.
How Term Length Affects Total Interest
Longer terms lower your monthly payment but increase the total interest you pay, often dramatically. The reason is that you spend more months at higher balances, where interest accrues fastest.
Here’s what a $50,000 loan at 7% APR looks like across common RV terms:
| Term | Monthly Payment | Total Interest | Total Cost |
|---|---|---|---|
| 120 months (10 yr) | $581 | $19,680 | $69,680 |
| 180 months (15 yr) | $449 | $30,880 | $80,880 |
| 240 months (20 yr) | $387 | $42,960 | $92,960 |
The 20-year term saves you $194/mo compared to the 10-year term, but you pay over $23,000 more in interest. That’s why stretching to 20 years costs so much more than most buyers expect.
What Happens When You Roll Costs Into the Loan
Every extra dollar added to the principal (sales tax, dealer fees, extended warranty, GAP insurance, negative equity from a trade-in) earns interest for the entire remaining term. On a 15- or 20-year loan, even a few thousand dollars of rolled-in costs can add up to significant extra interest.
Example: Rolling $3,000 of sales tax into a 180-month loan at 7% adds about $1,940 in interest over the life of the loan. That $3,000 really costs $4,940.
You can estimate the interest on your full deal by toggling individual costs in and out of the loan to see how each one changes your payment and total interest.
How Refinancing Resets Amortization
When you refinance, you start a new amortization schedule from scratch. Even if your new rate is lower, you go back to month 1 where interest dominates each payment.
This matters because if you’re several years into a loan, a growing share of your payment is already going to principal. Refinancing can lower your monthly payment but may increase total interest if the new term is longer, which is how refinancing resets your amortization clock.
The key question is whether the rate reduction saves enough to offset the cost of resetting. That’s what a break-even calculation answers.
Key Takeaways
- RV loans use simple-interest amortization: fixed payment, shifting principal/interest split
- Early payments are interest-heavy; equity builds slowly at first
- Longer terms lower payments but dramatically increase total interest
- Every dollar rolled into the loan (tax, fees, add-ons) earns interest for the full term
- Refinancing restarts the amortization clock - lower rate doesn’t always mean lower total cost
Sources
- Consumer Financial Protection Bureau - What is amortization? - Federal explainer on how amortization works on installment loans.
- Investopedia - Simple Interest - How daily simple interest accrual works on auto and RV loans.
- Investopedia - Amortization - Detailed breakdown of the amortization formula and principal/interest split over time.