A. O. SMITH TK-510U-E 2**
0.81 UEF DOE CCD · 2026-09-19Grade G: where this UEF sits among the 397 models in its class, lowest (G) to highest (A). A position, not an official label. How the grade is set
A gas tankless unit, high draw pattern (a larger household, or one where showers and laundry overlap).
If you are verifying the A. O. SMITH TK-510U-E 2**, it uses 209 therms of natural gas a year. That figure is for the high draw pattern, the standard daily hot-water usage DOE tests against. It sits 27 therms above the 182 therms median of the 397 gas tankless models registered at that pattern.
Energy use per year
209 therms a year
Computed by this site from the registry's UEF and the federal test's daily hot-water draw for this draw pattern. What it costs depends on the natural gas rate where you live.
That is above the median of 182 therms for the 397 models registered in the same heater type and draw pattern; it ranks 323 of 397, lowest energy first.
Solid line: this model (209 therms). Dashed line: the class median.
Min 173 therms Median 182 therms Max 209 therms
What it costs to run where you live
What the registry files
- UEF (Uniform Energy Factor) how much hot water you get for each unit of energy the heater uses
- 0.81 DOE CCD · 2026-09-19 Compared only with other models registered as a gas tankless unit at the high draw pattern.
- Draw Pattern the standard daily usage profile DOE tests the unit against
- High DOE CCD · 2026-09-19
- Maximum Gallons Per Minute how many gallons a minute it can heat while running continuously
- 5 gal/min DOE CCD · 2026-09-19
What it costs to install
$1,698–$2,632 installed
Not a quote — a modeled range of what installers have charged for this class of unit; your price will vary with labor rates, access, and local code requirements.
Escalation indexes: equipment (BLS PPI) latest available: August 2026; labor (BLS ECI) latest available: April 2026 to June 2026.
NLR REMDB (BLS PPI/ECI escalated) · 2026-04-01Safety record
No CPSC recall names this model.
Checked against the CPSC recall database. CPSC does not publish a model-level match for this product category, so this list is curated by hand from the manufacturer's recall filings.
CPSC · 2026-09-24What these figures mean
How this compares
The closest models in the same class — same fuel, type and draw pattern.
Keep going
How every figure on this page is calculated
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Find what replaces your water heater
Enter the model number off your old unit and see what is on file today, with the yearly cost difference.
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Find a water heater that fits
Three questions — fuel, hot water need, install space — narrow every model on file to the ones that fit.
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What a water heater costs to run
Prices a unit's efficiency against your own utility's filed tariff for your ZIP code.
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How to size a tankless water heater by GPM
Answered from what models in this size actually file.
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Water heaters
Every model on file with the Department of Energy, by heater type.
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All gas tankless water heaters
Gas-fired instantaneous units, sized by flow rate rather than tank gallons.
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Every A. O. SMITH model on file
What this brand files, by heater type.
UEF 0.81 · Grade G Price it on your ZIP
This site calculated the 209 therms figure. The registry does not publish it. The calculation combines the registry's UEF, the ratio of hot water delivered to energy used, with the daily hot-water draw in the DOE test for the high pattern. This model's UEF is 0.81, from the DOE Compliance Certification Database, retrieved 2026-09-19. The figure therefore holds only at that test draw. A home drawing more or less hot water each day will use a different amount of gas. The registry also lists a maximum flow rate in gallons per minute of 5 for this unit. The annual figure does not use that flow rating, so the rating does not change it. The steps are set out on the page explaining how the annual cost is calculated.
Within its class, the A. O. SMITH TK-510U-E 2** ranks 323rd lowest energy use of 397 gas tankless models at the high draw pattern. That puts it in the highest quarter of its class for energy use. Every model ranked ahead of it uses less gas at the same test draw. The high pattern stands for a larger household, or one where showers and laundry overlap. For a home like that, 209 therms is the closest registry reference for yearly gas use. For a smaller household, the figure does not apply directly, because its daily draw would differ from the test draw. The registry data here do not cover comfort, noise or service life, so this page cannot say anything about them. To compare it with other units in the same class, use the tool to find a same-class replacement by model number.
This text does not state a running cost. It depends on your state's average residential gas price, which the registry does not record. The page calculates it from your ZIP by applying that price to 209 therms a year at the high draw pattern. The 27 therms gap to the class median converts to cost the same way, on the same rate. For a figure based on your own rate, use the cost calculator for your own ZIP. The installed price range appears in its own block on this page, with its source and date. It is a modeled range, not a quote. The registry does not show what any single home will pay to run this unit.
DOE CCD · 2026-09-19