HVAC Contractor Demand Letter (With State-Aware Template)

What to include in an HVAC demand letter

An effective HVAC demand letter goes beyond the standard template. It should include your contractor license number and any HVAC-specific certifications (EPA 608, NATE), the property address where work was performed, a detailed description of the work including equipment model numbers and serial numbers, the original estimate or proposal (attached), any change order documentation, permit numbers and inspection results if applicable, the total owed including late fees, and a specific payment deadline.

Equipment serial numbers are particularly important for HVAC demand letters. They prove that you installed specific, traceable equipment in the client's home. If the dispute goes to court, you can demonstrate that a $3,200 Lennox condenser with serial number XYZ is currently sitting in the client's backyard.

Include a reference to your state's prompt payment act. Every state has one, and many have specific provisions for construction trades including HVAC. For example, Texas prompt payment requires owners to pay within 35 days of receiving your invoice. California requires payment within 30 days of completion. Florida gives 20 days for progress payments on residential construction.

If you installed equipment, mention that you retain a security interest in the equipment until paid in full (if your contract includes this language). While repossessing a furnace is rarely practical, the legal concept of a security interest in installed equipment adds leverage.

Demand letter for AC installation disputes

AC installation disputes typically involve price disagreements after the emergency has passed. Your demand letter should emphasize: the emergency nature of the call (date, temperature, client's description of the situation), the options you presented (repair vs. replace, different equipment tiers), the client's selection and approval, and the work timeline.

For example: 'On July 14, 2025, you contacted our office requesting emergency service for a non-functioning air conditioning system at [ADDRESS]. The outdoor temperature was 97 degrees. Our technician diagnosed a failed compressor in your 15-year-old Goodman unit and presented three options: compressor replacement ($2,800), mid-range system replacement ($6,200), and high-efficiency system replacement ($8,400). You selected the mid-range replacement and signed the attached proposal.'

This level of detail makes the demand letter much harder to dispute. The client cannot claim they did not approve the work when you have documented the options presented and the selection made. If you presented options via text or email, attach those communications.

For the $6,000-$8,000 range that most residential AC replacements fall into, a demand letter produces payment roughly 60-70% of the time without needing to file a lien or go to court.

Demand letter for furnace replacement disputes

Furnace replacement disputes follow a similar pattern to AC disputes but with a winter twist. The client approved the work during a cold snap, the furnace was replaced within 24-48 hours, and now they want to negotiate the price after they have been warm for two months.

Your demand letter should document: the date and circumstances of the service call, the diagnosis (cracked heat exchanger, failed ignitor on a 20-year-old unit, etc.), the safety implications of the existing condition (a cracked heat exchanger is a carbon monoxide risk), the options presented and selected, and the equipment installed with model and serial numbers.

Safety language adds weight to furnace demand letters. If you condemned a furnace due to a cracked heat exchanger, state it plainly: 'Our technician identified a cracked heat exchanger in the existing furnace, creating a carbon monoxide risk. In accordance with building code and manufacturer guidelines, the unit was condemned and could not be restarted. Replacement options were presented and you selected the [MODEL] furnace.' A client disputing a safety-driven replacement looks unreasonable to any judge.

Furnace replacement invoices typically range from $3,500-$7,000 for standard residential units. At these amounts, small claims court is accessible if the demand letter does not produce payment.

Demand letter for maintenance contract breaches

Maintenance contracts are recurring revenue, and when clients cancel mid-term after receiving services, you need to recover the value delivered. The demand letter approach depends on your contract language.

If your contract includes an early termination fee, reference it directly: 'Per Section 4 of the Service Agreement dated [DATE], early termination within the first 12 months requires payment of [AMOUNT] to cover services already rendered at their non-discounted rate.' A common structure is that the two annual tune-ups are valued at $149 each at non-contract rates, so a client who received one tune-up and cancels owes $149 minus whatever monthly payments they have made.

If your contract does not have termination language, you can still recover the fair value of services rendered. A spring tune-up that would cost $149 a la carte was provided as part of a $39/month plan. If the client cancels after 3 months ($117 paid), they owe the difference of $32 plus any other services used at their non-contract rate.

The amounts in maintenance contract disputes are usually small ($100-$500), but pursuing them sets a precedent. If you let clients cancel mid-contract without consequence, word gets around. Send the demand letter on principle.

State prompt payment act references for HVAC contractors

Your demand letter gains legal weight when it references specific statutes. Here are the key provisions HVAC contractors should cite:

Texas: Property Code Chapter 28 (mechanics liens) and Government Code Chapter 2251 (prompt payment). Owners must pay within 35 days. Interest on late payments accrues at 1.5% per month.

California: Civil Code Sections 8000-9566 (mechanics liens). Business and Professions Code Section 7159 (home improvement contracts). Payment due within 30 days of completion. Preliminary 20-day notice required to preserve lien rights.

Florida: Chapter 713 (Construction Lien Law). Owners must pay within 20 days (residential) or per contract terms (commercial). Interest at 1% per month or the contract rate, whichever is higher. Notice to Owner required within 45 days of first furnishing labor or materials.

These references signal to the client that you know your rights and are prepared to enforce them. Most homeowners have never heard of a prompt payment act, and seeing a specific statute cited in your demand letter changes the dynamic from 'contractor asking for money' to 'contractor exercising legal rights.'

After the demand letter: HVAC-specific next steps

If the demand letter does not produce payment within 10-14 days, your next step depends on the amount and situation.

For residential AC and furnace installs ($3,000-$8,000): File a mechanics lien on the property. The lien attaches to the real estate and prevents the homeowner from selling or refinancing. For an HVAC system that is physically attached to the home, lien rights are well-established in every state. Filing costs $50-$200 in most counties.

For commercial HVAC work ($10,000+): If the project is bonded, file a payment bond claim in addition to or instead of a mechanics lien. The bond exists specifically to protect subcontractors and material suppliers. Bond claims are especially effective because the surety company processes the claim and pays you directly.

For maintenance contract disputes (under $1,000): Small claims court is the most cost-effective option. Filing fees are $30-$75, and you can typically get a hearing within 30-60 days. Bring your signed contract, records of services performed, and your demand letter.

For all scenarios, InvoiceFlows generates demand letters that automatically include the correct prompt payment act references for your state, your HVAC license number, and equipment details from your original invoice. This saves the 2-3 hours it typically takes to research statutes and draft a letter from scratch.