Two homeowners posting about nearly identical projects on the same weekend found themselves quoted $5,250 and $8,709 respectively for what sounds like comparable tankless installation work. Understanding why that gap exists is more useful than any single average number could be.
Budget $2,500 to $9,000 for total installed cost of a Rinnai RXP199iN or similar high-capacity condensing tankless unit, with the wide range driven primarily by whether you’re converting from a tank system (requiring new gas line work) versus replacing an existing tankless unit, plus regional labor rate differences documented across real homeowner quotes. The unit price itself (approximately $1,735.53 for the RXP199iN) represents only a portion of this total, often less than a third of the overall project cost for a first-time tank-to-tankless conversion.
Breaking Down Where the Money Goes
Based on real quotes and cost breakdowns found across multiple sources, a typical tankless installation budget splits roughly into three categories: the unit itself (a fixed, known cost), gas line and venting work (the most variable cost, ranging from minimal if infrastructure exists to several thousand dollars for a full new gas line run), and general labor for removal, plumbing connections, and system testing.
A Bogleheads forum post specifically itemized one real quote as “$3,168 for tankless, gas work, and labor” as a single combined figure, illustrating how these categories often get bundled into one number by contractors rather than itemized separately, another reason it’s worth asking for a detailed breakdown before accepting any quote.
Tank-to-Tankless Conversion: Budget Toward the Higher End
If you’re switching from a traditional tank system to a Rinnai RXP199iN for the first time, budget toward the higher end of the range, commonly $6,000 to $9,000 based on multiple real reports including a specific $8,709 quote documented on Reddit and Endless Energy’s own published $5,999 to $9,000 range for Massachusetts installations. This reflects the genuine additional work required: new gas line sizing to support the unit’s higher BTU demand, and new venting infrastructure that a tank system never needed.
Tankless-to-Tankless Replacement: Often Meaningfully Cheaper
If you already have an existing tankless unit (including a previous-generation model like the discontinued RU199iN) and are simply replacing it with a current RXP199iN, your installation cost should land considerably lower, since the gas line and venting infrastructure required for tankless operation is typically already in place. This is the scenario reflected in the lower end of documented reports, historical figures like the $2,500 quote from 2012 in Oxford, Mississippi likely reflect this simpler replacement scenario rather than a full conversion.
Regional Variation Is Real and Significant
A Facebook thread specifically discussing a $6,300 quote in Franklin, Tennessee drew a comment attributing part of the cost to a regional “upcharge,” a reminder that identical work can carry meaningfully different price tags depending on your specific local market and cost of living.
How to Budget Responsibly
Start by determining whether your project is a tank-to-tankless conversion or a tankless replacement, since this single factor most reliably predicts which end of the cost range you should expect. Then get at least two to three itemized quotes specifically breaking out unit cost, gas line work, venting, and labor, so you can identify whether a low quote is genuinely competitive or missing scope that will surface as a change order later.
For the complete overview of installation steps and what’s typically involved, see our full installation guide.
Rinnai RXP199iN Condensing Tankless Water Heater with Built-In Recirculation Pump - View on Amazon
The Bottom Line
Budget $2,500 to $9,000 for a complete Rinnai RXP199iN installation, with tank-to-tankless conversions landing toward the higher end due to new gas line and venting work, and tankless-to-tankless replacements often coming in considerably lower since that infrastructure already exists.
Frequently Asked Questions
How much should I budget for a Rinnai RXP199iN installation? Based on real homeowner reports, budget $2,500 to $9,000 total, with tank-to-tankless conversions landing toward the higher end and tankless replacements often costing considerably less.
Why is a tank-to-tankless conversion so much more expensive? It typically requires installing a larger gas line to support the tankless unit’s higher BTU demand, plus new venting infrastructure that a tank system never needed.
Is replacing an existing tankless unit cheaper than converting from a tank? Yes generally, since gas line sizing and venting infrastructure are typically already in place from the previous tankless installation.
What’s a normal price range for this type of installation? Real reported figures range from $2,500 to over $8,700, with Endless Energy publishing a $5,999 to $9,000 range specifically for full conversions in Massachusetts.
Does location affect installation cost? Yes significantly, one Facebook discussion specifically attributed part of a $6,300 quote to a regional cost upcharge, confirming real geographic price variation.
Should I be worried if I get a very low quote? Not necessarily, but request an itemized breakdown to confirm the quote includes all necessary gas line, venting, and labor work, rather than assuming scope that might surface as an added cost later.
What percentage of total cost is the unit itself? For a full tank-to-tankless conversion, the unit price (around $1,735.53 for the RXP199iN) often represents less than a third of the total installed cost once gas line and venting work are included.
How can I get a fair, accurate quote? Get at least two to three itemized quotes specifically breaking out unit cost, gas line work, venting, and labor, and confirm whether your project is a conversion or a straightforward tankless replacement.
Does the RXP199iN’s built-in recirculation pump add installation cost? It may require additional dedicated wiring or plumbing for the pump function depending on your setup, worth confirming directly with your installer during the quoting process.
Is it worth shopping around for installation quotes? Yes, given the documented 3x+ variation for seemingly comparable work found in real reports, getting multiple quotes is a genuinely worthwhile step before committing to an installer.
References
- Reddit r/askaplumber and Bogleheads Investing forum discussions of real Rinnai tankless installation costs, accessed July 2026
- Endless Energy, “The 2025 Cost of Tankless Water Heaters in Massachusetts,” accessed July 2026: https://goendlessenergy.com
- Facebook community discussions of regional tankless installation pricing, accessed July 2026