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Three quarters of residential water heater replacements happen because the old unit failed. Efficiency programs are rarely there when it does.
That first number is well documented, and the second half is visible in program data. Research from the Northwest Energy Efficiency Alliance found that roughly 75% of water heater replacements in existing homes follow a failure, split between sudden failures and units replaced just ahead of an expected failure, with plumbing contractors reporting the real share is higher still. A 2024 CalNEXT study of emergency replacement found the mirror image: in California's flagship heat pump water heater program, emergency replacements accounted for only about nine percent of installations.
The volume is in one place. The programs are in another.
What the emergency actually looks like
It is worth being precise about the moment itself, because program design tends to assume a shopper, and at the moment of failure there isn't one.
The tank fails. The customer calls a plumber. NEEA's research identified three drivers of what happens next: the customer wants a unit similar to the one they had, they need it now and do not want to research alternatives, and they are focused on upfront cost rather than long-term savings. The DOE's market profile for water heaters made the structural point plainly years earlier: installers and retailers are the primary points of influence, and often the sole source of advice for purchasers.
So the typical outcome is one installer, one product, one price. No comparison, no visible market, no efficiency conversation. In California alone, roughly 721,000 water heaters are replaced each year in single-family homes. About 87% of them are gas, and 85% of those gas units are replaced with gas.
None of this is a failure of the trades. It is a structural feature of an urgent purchase made once every ten to fifteen years, where the customer has no price reference and no time to build one, and where nobody in the transaction has a repeat-business incentive to supply one.
The uncomfortable finding about rebate levels
The instinct when a program underperforms is to raise the incentive. The CalNEXT study contains a finding that should give anyone pause before doing that.
Comparing project costs across California territories, the study team observed that higher, stackable incentives in one gas utility's service area correlated with installed project costs roughly $2,000 higher than in other parts of the state. They hypothesize, without claiming to have proven it, that higher rebate levels allow contractors to increase their quotes to customers.
Read that from the program side. In a transaction with no price transparency, part of the incentive can end up funding the price rather than reducing it. The customer's out-of-pocket cost does not fall as designed, the cost-effectiveness math weakens, and the program has less to show for the same money. The rebate was never the thing that was broken. The absence of a visible market price was.
Reach, not level
Consider how residential water heater incentives are typically delivered.
Post-purchase rebates ask the customer to file paperwork weeks after a purchase they made in a panic.
Coupon programs at participating retailers ask the customer to verify eligibility, obtain a code, and travel to a specific store that has the unit in stock, all before buying.
Midstream and distributor programs put the incentive into the supply chain, which is much closer to the moment, but leave two decisions with the person on the truck: whether to offer the efficient option at all, and whether to pass the discount through.
Each of these can be an instant discount at the point of sale. None of them is reliably available at the point of panic. That is the design gap, and it is not solved by adding dollars to the incentive. Reach and transparency matter more than rebate size, and they are really one problem rather than two.
The second constraint nobody budgets for
Suppose you fix reach. A customer whose tank failed this morning can now see the whole market, with the incentive already netted out of the price, and a monthly payment option if they cannot absorb the cost up front. That last piece matters more than it sounds: survey data continues to show that a majority of American households do not have $1,000 available for an unplanned expense.
You have created demand at exactly the moment it exists. Now you have to deliver installed units, in volume, in days. Equipment availability, professional installation, permitting, haul-away. In our experience, this is where water heater programs actually stall. Incentive design is the easier half of the problem. Fulfillment at volume is the half that decides whether the program is real.
What happens when a program is there
Last program year, a large natural gas utility in Southern California ran a marketplace program with us, designed against the replacement moment: the full market visible with an efficiency score on every model, the instant rebate applied at checkout, low-APR financing embedded, and fixed-price professional installation scheduled in the same flow.
A single customer email produced 557 efficient water heater orders in one day. Sustained volume ran at dozens of orders per day for months. About one in six participants came from a disadvantaged community, and for anyone carrying equity targets, that is the number worth watching, because affordability at checkout is what moves it. The program committed its entire annual incentive budget by the end of the first quarter.
That last fact usually gets reported as a problem. It is better understood as a measurement. Demand was never the constraint. The constraints were the rebate level, and a budget sized to participation rates from a channel that never reached the failure moment.
A design checklist
If you are evaluating your own water heater program, five questions get you most of the way.
- Can a customer whose unit failed this morning access your incentive today, without a store visit, a form, or a contractor's initiative?
- Is your incentive visible against a market price the customer can verify, or is it applied to a quote they cannot check?
- Can a customer who does not have $1,000 on hand still choose the efficient unit?
- If participation tripled, would the fulfillment chain deliver installed units, or would the program stall below its incentive budget?
- Is your budget sized to demonstrated demand at the replacement moment, or to historical participation from a channel that never reached it?
The last question is the one that tends to reshape a filing.
We built a model that answers the sizing question with your own numbers. Enter your territory, your fuel path, and your rebate level, and it projects installs, energy savings, and the incentive budget your program would actually need, including the month the funding would run out. Every assumption is editable, including per-unit savings from your own technical reference manual.