Product images: Amazon listings
Written from the listing and 266 buyer reviews, not from our own use · How we rate
On paper, the SIVUATEK 18 kW Electric (240V) gets the important things right: up to 4.3 GPM, 18 kW of heating power and self-modulating power. Rated 7.7/10, it suits a smaller home or one main bathroom on electric.
| Brand | SIVUATEK |
|---|---|
| Category | Electric tankless water heaters |
| Fuel | Electric |
| Stated maximum flow | 4.3 GPM |
| Stated heating power | 18 kW |
| Stated voltage | 240 V |
| Wire gauge | 8 AWG |
| Buyer reviews | 266 · 4.4/5 |
| ASIN | B0BBT4ZR9R |
Full listing title: 18kW Tankless Water Heater Electric 240V,Self-Modulating
| Fuel | 18kWFull listing title |
|---|---|
| Stated maximum flow | up to 4.3GPMListing text |
| Stated heating power | 18kWFull listing title |
| Stated voltage | 240VFull listing title |
Not in our top-5 rankings
What it's made for: a smaller home or one main bathroom on electric.
Two electric tankless heaters of about the same power, closest to it on our rating, each with a dated price.
The heating power the listing states. At 240 V it draws about 75 A, on 8 AWG wire per the listing. That's the line to show your electrician before anything else: the panel decides whether this fits, not the shower.
What it has going for it
4.3 GPM max. That is the headline figure, usually at a modest temperature rise. Our calculator counts a shower at 2 GPM, so think one shower at a time.
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: where it comes in around 62 °F (much of the South), 18 kW gives about 2.9 GPM of 105 °F water on our calculator's maths. That's one 2 GPM shower at a time.
A cold January: where it comes in at 42 °F, it's about 1.9 GPM, less than one 2 GPM shower. Up north, that's the figure to size against, and it's why the honest answer is sometimes a second unit or gas.
What the SIVUATEK 18 kW Electric (240V) listing names:
For the SIVUATEK 18 kW Electric (240V), the installation manual settles the breakers and the wire.
At the price on Sep 30, 2026, each kW of stated heating power works out at about $13.67 (price ÷ stated kW, our arithmetic). That puts it in the cheaper third 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 B0BBT4ZR9R), where today's price, stock and seller apply.
Colder tap water where you live? The WINTEMP WN-36kW Electric, 240V (8.1/10) is rated 36 kW.
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 SIVUATEK 18 kW Electric (240V) earns its place with up to 4.3 GPM and 18 kW of heating power. 266 buyers give it 4.4/5, which is a solid sign. Our main reservation: no word on the breakers it needs. Before you decide, put it next to the Stiebel Eltron Tempra 29 Plus.
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.
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, then leave it.
With 42 °F water coming in, 18 kW gives about 1.9 GPM at 105 °F on our calculator's maths. Low-flow shower heads stretch that further.
Clean the inlet screen and flush out scale on hard water. Our flushing and descaling guide has the routine.
Buyers give it 4.4/5, a strong record, above our ranked picks' 4.3 average. 266 reviews is a fair sample, enough for the average to mean something.
Before the SIVUATEK 18 kW Electric (240V) goes in your cart, check your panel: 18 kW at 240 V is roughly 75 A, so an electrician should look at the panel first.
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.
On our calculator's maths, 18 kW gives about 1.9 GPM with 42 °F winter water and 2.9 GPM with 62 °F water. Our flow-rate calculator does it for your region.
Hardwired 240 V work needs a licensed electrician and often a permit. Our install cost guide shows what usually ends up on the quote.
Hard water still builds up on the elements and the inlet screen. Our flushing and descaling guide covers the routine.
How the SIVUATEK 18 kW Electric (240V) stacks up against the closest alternative, the Stiebel Eltron Tempra 29 Plus.
| Criterion | SIVUATEK 18 kW Electric, 240V | Stiebel Eltron Tempra 29 Plus |
|---|---|---|
| Our rating | 7.7/10 | 7.9/10 |
| Heating power | 18 kW | 28.8 kW |
| Max flow | 4.3 GPM | Not stated |
| Breakers | Not stated | 200 A total |
| Self-modulating | Stated | Not stated |
| Buyer reviews | 266 · 4.4/5 | 451 · 4.4/5 |
Pick the Stiebel Eltron Tempra 29 Plus if you want our higher-rated option (7.9/10), with more power (28.8 kW); stay with the SIVUATEK 18 kW Electric (240V) for more stated flow (4.3 GPM) and self-modulating power.
We rate it 7.7/10 (very good). It is based on 266 buyer reviews averaging 4.4/5 and the specifications stated in the listing.
The listing states a maximum flow of 4.3 GPM and a heating power of 18 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.
The listing states 240 V and 18 kW. At 240 V, that is roughly 75 A. A licensed electrician checks the panel, the breakers and the wiring before it goes on the wall.
Its listing states up to 4.3 GPM, 18 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.
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, 18 kW gives about 1.9 GPM with 42 °F winter water and 2.9 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.
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.
No, we haven't used it ourselves. Everything on this page comes from its listing and 266 buyer reviews, read line by line and weighed with our published formula.