A service maintenance agreement doesn't just need a good price - it needs added value. Though the agreement extends the life of a customer's system, prevents otherwise fatal mistakes, and is a good regular home practice, your customer wants more. More might mean providing services and products with a higher perceived value, but that will only cost you more time.
Aside from the 24-hour emergency service your business should already be offering, provide flexible hours (including nighttime and Sundays). Your customer will thank you over and over for accommodating his or her schedule.
System upgrade prices
Offer a discounted service maintenance agreement with upgrade - or vice versa. Be careful, however, to not price too low or short-circuit the actual value of the special package you offer.
Thank your customer
Is your customer still not convinced? Fear not. If they say "no" at first, send them a thank you note no more than a week after your house call, and remind him or her about the need for that maintenance agreement.
Value will keep your customer coming back and asking for more maintenance agreements.