Service
Electric tankless water heater installation
Whole-house electric tankless units draw more current than most other appliances in a home. The wiring decides whether one fits.
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Written by HyreElectrical Research Desk Primary-source research and fact checking
The short answer
Electric tankless water heater installation is a job for a licensed electrician and often a plumber: whole-house units can need two to four large 240-volt circuits, so the panel and service must have room. The heater’s manual sets the breaker and wire sizes. The first step is a load calculation, not a purchase.
Why the electrical side is big
A tank heater warms water slowly. A tankless unit heats it as it flows, so it draws a lot of current at once. Manufacturer manuals specify the number and size of circuits; whole-house models often need several.
Many older 100-amp services cannot carry that load on top of HVAC and a range. An electrician runs an NEC Article 220 calculation to check. Try our load calculator for a rough look.
What the job includes
New two-pole breakers and heavy-gauge cable for each circuit, a disconnect where required, and connection to the unit. The plumber handles water lines. If the service is short, the job grows into a panel upgrade.
Point-of-use units under a sink are smaller and may need only one circuit.
Permit, time and what changes the price
Expect electrical and plumbing permits.
Price drivers: number and size of circuits, distance from the panel, panel spaces, service upgrade if needed, and permits. No price ranges are published here until we hold enough sourced, dated quotes; see cost guides.
Ask before you buy
Check the manual for the circuit list and compare it with your panel and service. Ask the electrician whether your house can carry it with existing loads.
Heat-pump water heaters are another electric option with smaller circuits. Check the license on your state board before anyone starts: how to check an electrician license.
What a fair written quote lists
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A person reads it and replies, free and with no obligation. Matching is not live yet, so this is not a quote or a dispatch line. If you smell burning or see sparks, stop using the circuit and call a licensed electrician now.
Find a Local Electrician
A person at HyreElectrical reads the request and replies. Matching is not live yet, so this is not a quote or a dispatch line.
Questions
How many circuits does a tankless heater need?
Will I need a panel upgrade?
Can I reuse my old water heater circuit?
Do I need a plumber too?
Written and audited by
HyreElectrical Research Desk
Primary-source research and fact checking
We read the model code, the federal safety notice, the municipal fee sheet or the utility tariff ourselves, and we publish the figure with the document it came from and the date we retrieved it.
Where a number cannot be traced to a primary source, we publish the shorter page and say what we could not verify. HyreElectrical does not perform, supervise or warrant electrical work. Authorship is organizational: this desk, not a named persona.
- 16
- original research studies published
- 5
- states with verified license records
- 16,369
- electrical companies in those records
- 74%
- of the store is Florida — disclosed first, not footnoted
How this desk works
- Primary sources only. Code statements come from NFPA 70 as the model code. Safety statements come from CPSC. Permit fees come from the city or county fee sheet. Utility charges come from the filed tariff. We do not cite a blog that cites a source; we open the source.
- Our contractor store is five states, and 74% of it is Florida. Any figure built on that store is titled to those states and names the concentration in the first screen. It is not a national sample of electricians.
- Load calculations on this site are a published simplification in the shape of NEC 220.82 — first 10 kVA at 100%, remainder at 40%, HVAC at 100%, EVSE at 125%. They are labeled as not a stamped calculation. A licensed electrician using the adopted edition does that work.
- No national price for a panel upgrade is shipped. Labor rates, the adopted code edition, whether the utility is involved, and the state of the existing wiring move the invoice too far for a roundup to help. The cost pages publish named permit fees and the variables that move the price instead.
- We do not perform electrical work, and we take no payment for placement, ranking or a favorable mention. Nobody buys a position on this site.
Authorship on this site is organizational: the analysis belongs to the desk rather than to a named individual, and we do not publish credentials we do not hold. Our editorial policy sets out how we source, date and correct what we publish.
Sources & retrieval dates
HyreElectrical is a publisher. It does not perform, supervise, inspect or warrant electrical work, holds no electrical license, and matching is still being built, so an inquiry is not a service call.
This page is general information, not a diagnosis or a quote. Code rules vary by the NEC edition your state or city adopted and its local amendments.