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ThermoMate 27 kW Electric Review

Name: ThermoMate 27 kW Electric
Brand: ThermoMate
SKU: B0H2P7NHYJ

6.2Fair · out of 10Not in our top-5 rankings

Written from the listing and 36 buyer reviews, not from our own use · How we rate

If you're after a 6.6 GPM maximum flow, the ThermoMate 27 kW Electric delivers, with 27 kW at 240 V and an element that only draws what it needs on top. A good match for two showers at once where gas is not an option, with 36 buyer reviews averaging 4.7/5.

Price$446.49Price on Sep 30, 2026 · may have changed

Check the price on Amazon ↗Affiliate link · price and stock on Amazon

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Specifications

Brand	ThermoMate
Category	Electric tankless water heaters
Fuel	Electric
Stated maximum flow	6.6 GPM
Stated heating power	27 kW
Stated voltage	240 V
Temperature range	80 to 140 °F
Total current	150 A
Wire gauge	8 AWG
Stated weight	16 lb
Buyer reviews	36 · 4.7/5
ASIN	B0H2P7NHYJ

Full listing title: ThermoMate 27kW Tankless Water Heater Electric Max 6.6 GPM ETL Certified

Listing evidence

Fuel	27kW Full listing title
Stated maximum flow	6.6 GPM Full listing title
Stated heating power	27kW Full listing title
Stated voltage	240V Listing text

Updated October 2026

Exact listing, ASIN B0H2P7NHYJ

Rating from a published formula

Compared with its closest rivals

Two electric tankless heaters of about the same power, closest to it on our rating, each with a dated price.

Compare side by side ↗

ThermoMate 27 kW Electric

6.2Fair · out of 10$446.49 Price on Sep 30, 2026 · may have changed

Stated: 6.6 GPM · 27 kW · 240 V
36 buyer reviews
Electric tankless water heaters

This product ↑

Garvee 27 kW Electric, 240V

6.3Fair · out of 10$192.99 Price on Sep 30, 2026 · may have changed

Stated: 27 kW · 240 V
4 buyer reviews
Electric tankless water heaters

See the review ↗

Bosch Tronic 6100, 27 kW

6.6Good · out of 10$636.60 Price on Sep 30, 2026 · may have changed

Stated: 27 kW
Electric tankless water heaters

See the review ↗

27 kW at 240 V

The heating power the listing states. At 240 V it draws about 113 A, on 8 AWG wire per the listing. Show that to your electrician first. Whether your panel has the room is the whole question, and the shower comes second.

What it has going for it

What changes in the morning shower rush

6.6 GPM max. That is the headline figure, usually at a modest temperature rise. Our calculator counts a shower at 2 GPM, so think two showers and a kitchen tap on paper, less when the water comes in cold.

Self-modulating. It draws only the power the flow and the setpoint need, instead of slamming every element on. Steadier temperature, and no wasted amps on a summer afternoon.

Warm tap water or a cold January?

Warm tap water: where it comes in around 62 °F (much of the South), 27 kW gives about 4.3 GPM of 105 °F water on our calculator's maths. That's two 2 GPM showers at once.

A cold January: where it comes in at 42 °F, it's about 2.9 GPM, one 2 GPM shower at a time. Up north, that's the figure to size against, and it's why the honest answer is sometimes a second unit or gas.

Great for you if…

You run one shower and the kitchen tap at once, rarely more
Your house has no gas and a 200 A panel with room to spare
You want the shower temperature to stay put

Skip it if…

Your panel is 100 A or already busy: 27 kW at 240 V is about 113 A on its own
You want a long review record: only 36 buyer reviews so far

Power, wiring and what's in the box

What the ThermoMate 27 kW Electric listing names:

27 kW
240 V
150 A total draw
8 AWG wire
Up to 6.6 GPM
Self-modulating
80 to 140 °F setpoint
16 lb
CSA, ETL or UL mark named

Breakers and wire gauge are in the installation manual, and it overrides anything above; your electrician reads it first.

Price and cost per kW

$446.49 Price on Sep 30, 2026 · may have changed

At the price on Sep 30, 2026, each kW of stated heating power works out at about $16.54 (price ÷ stated kW, our arithmetic). That puts it around the middle of the 27 whole-house electric tankless heaters we have a price and a stated power for.

Budget for the electrician as well: new double-pole breakers, thick wire from the panel and, if the panel is full, an upgrade.

The button opens the exact listing (ASIN B0H2P7NHYJ), where today's price, stock and seller apply.

A better fit for your house and panel?

Colder tap water where you live? The WINTEMP WN-36kW Electric, 240V (8.1/10) is rated 36 kW.

Panel short on spare amps? The Rheem 18 kW Electric, 240V (9.3/10) is rated 18 kW, about 75 A at 240 V.

Only one sink far from the heater? The ThermoMate 14 kW Electric, 240V (7.9/10) is a 14 kW point-of-use unit.

Our take

The verdict

What we'd buy the ThermoMate 27 kW Electric for is a 6.6 GPM maximum flow, with 27 kW at 240 V as a bonus. Only 36 buyers have rated it so far (4.7/5), so treat the score as an early read. The one thing that bugs us: the heater is the cheap part next to the panel work an electrician may need. We'd pick it if you run one shower and the kitchen tap at once, rarely more; otherwise, put it next to the Garvee 27 kW Electric (240V) first.

Check the price on Amazon ↗Affiliate link · price and stock on AmazonAll electric tankless water heaters →

Living with it

Install day

New breakers, 8 AWG wire, the unit on the wall next to the old tank's spot, water in and out. An electrician does the panel side.

The first shower

Hot in a few seconds once the water in the pipes has passed, and the power steps up and down with the flow (self-modulating, per the listing). Set it between 80 and 140 °F.

The first winter

With 42 °F water coming in, 27 kW gives about 2.9 GPM at 105 °F on our calculator's maths. Low-flow shower heads stretch that further.

Upkeep

Clean the inlet screen and flush out scale on hard water. Our flushing and descaling guide has the routine.

What buyers say

Buyers give it 4.7/5, an excellent record, well above our ranked picks' 4.3 average. Only 36 reviews so far, and our formula damps averages built on fewer than 50.

The numbers

Buyer rating: 4.7/5
Reviews: 36
Ranked picks' average: 4.3/5

The one thing we'd check first

Before you order the ThermoMate 27 kW Electric, check your panel: it draws 150 A, so an electrician should look at the panel first.

Before you buy

Your panel

Take a photo of the panel label (main breaker size and free slots) and send it to the electrician with the listing. Our electrical requirements guide explains what they will look for.

Your winter flow

On our calculator's maths, 27 kW gives about 2.9 GPM with 42 °F winter water and 4.3 GPM with 62 °F water. Our flow-rate calculator does it for your region.

The install

Hardwired 240 V work needs a licensed electrician and often a permit. Our install cost guide shows what usually ends up on the quote.

Scale

Hard water still builds up on the elements and the inlet screen. Our flushing and descaling guide covers the routine.

How it compares

How the ThermoMate 27 kW Electric stacks up against the closest alternative, the Garvee 27 kW Electric (240V).

Criterion	ThermoMate 27 kW Electric	Garvee 27 kW Electric, 240V
Our rating	6.2/10	6.3/10
Max flow	6.6 GPM	Not stated
Breakers	150 A total	Not stated
Buyer reviews	36 · 4.7/5	4 · 4.7/5

Pick the Garvee 27 kW Electric (240V) if you want our higher-rated option (6.3/10); stay with the ThermoMate 27 kW Electric for more stated flow (6.6 GPM).

Compare side by side ↗See the Garvee 27 kW Electric, 240V review →

The score in detail

How we rated it

Our score: 6.2/10

Buyer rating (45%)

30.5 / 45

4.7/5 average, confidence-damped (36 reviews < 50)

Review volume (35%)

14.8 / 35

36 buyer reviews

Documented specifications (20%)

17.2 / 20

86/100 listing documentation score

Our rating is an evidence index on a 0–10 scale. It is not a buyer star rating, and we have not used the product ourselves.

Buyer rating (45%): the captured average for this exact listing, damped when there are fewer than 50 reviews.
Review volume (35%): more reviews mean more reliable evidence, on a logarithmic scale up to 5,000 reviews.
Documented specifications (20%): how completely the exact listing documents the attributes that matter.

Our editors then look at how it compares with the other heaters we rate. A commission is never an input to the rating. Read the full methodology.

Read the methodology →

Frequently asked questions

Is the ThermoMate 27 kW Electric any good?

We rate it 6.2/10 (fair). It is based on 36 buyer reviews averaging 4.7/5 and the specifications stated in the listing.

How much hot water can the ThermoMate 27 kW Electric deliver?

The listing states a maximum flow of 6.6 GPM and a heating power of 27 kW on 240 V. The headline flow is a mild-weather number: with cold winter water coming in, the same unit gives you less. Read the maker's flow chart at your winter rise, or let our flow-rate calculator do the sums.

What electrical service does the ThermoMate 27 kW Electric need?

The listing states 240 V and 27 kW. At 240 V, that is roughly 113 A. A licensed electrician checks the panel, the breakers and the wiring before it goes on the wall.

What do you get with the ThermoMate 27 kW Electric?

Its listing states up to 6.6 GPM, 27 kW of heating power and self-modulating power. These are the seller's figures, not our measurements: how steady the temperature is in your shower and how it copes with your winter water can't be read from a listing.

What should I check before ordering the ThermoMate 27 kW Electric?

Your panel: take a photo of the panel label (main breaker size and free slots) and send it to the electrician with the listing. Our electrical requirements guide explains what they will look for. Your winter flow: on our calculator's maths, 27 kW gives about 2.9 GPM with 42 °F winter water and 4.3 GPM with 62 °F water. Our flow-rate calculator does it for your region. The install: hardwired 240 V work needs a licensed electrician and often a permit. Our install cost guide shows what usually ends up on the quote. Scale: hard water still builds up on the elements and the inlet screen. Our flushing and descaling guide covers the routine.

Where can I buy the ThermoMate 27 kW Electric?

We link to the exact listing on Amazon, where today's price, stock and seller apply. It is an affiliate link, and it has no effect on the rating.

Have you used the ThermoMate 27 kW Electric yourselves?

No, we haven't used it ourselves. Everything on this page comes from its listing and 36 buyer reviews, read line by line and weighed with our published formula.

Electric tankless water heaters ↗All ThermoMate products Comparison tool All product reviews