As in the rest of Arizona, there is no SRP rebate for repairing or replacing a gas furnace — the state is heat-pump country and the electric utilities don't subsidize gas heat. For SRP customers in the East Valley, the genuine furnace-relevant incentive is Bring Your Own Thermostat: $50 to enroll a smart thermostat you already own and $25 per year to keep it enrolled, for up to two thermostats.
The thermostat is what makes this relevant to heating. A smart thermostat trims gas-furnace runtime in winter and AC runtime in summer; in return for letting SRP make brief, override-able adjustments during summer peak events, you collect the enrollment and annual credits. For a homeowner who just paid for a furnace repair, it's a small, fast way to offset some of the cost and lower the next bill.
Territory is the thing to verify first. SRP and APS interleave across metro Phoenix, and the two thermostat programs aren't interchangeable — BYOT is for SRP-metered homes (broadly Tempe, Mesa, Chandler, and Gilbert), while APS customers use Cool Rewards. Check your electric bill before enrolling.
Enrolling takes a few minutes: own a supported Wi-Fi thermostat — ecobee, Google Nest, and Honeywell Home models are generally eligible — connect it to your SRP account, and opt in. During a summer peak event SRP shifts your setpoint briefly and you can override it; the winter benefit is simply running the furnace on an efficient schedule, since the demand events themselves are summer-only.
SRP also runs Cool Cash rebates for high-efficiency air conditioners and heat pumps, which is the equipment-replacement incentive most Arizona homes can actually use, since they heat with a heat pump rather than a gas furnace. If your 'furnace' is in fact the heating side of a heat pump, ask about Cool Cash. For a true gas furnace, the repair-vs-replace decision rests on the unit's age and a combustion-analysis safety check, not on a rebate.