Stiebel Eltron Tankless Water Heater Installation: A Procurement Manager's Checklist for Cost-Effective Setup

Who This Checklist Is For

If you're a procurement manager or facilities lead at a mid-size company (think 50-200 employees), and you're looking into a Stiebel Eltron tankless water heater for an office, warehouse, or new build—this is for you.

I've been managing our service contracts and equipment purchases for the past 6 years. We've installed three Stiebel Eltron Tempra Plus units across two buildings. This checklist covers the 7 steps I follow every time. It's not about the technical hookup—it's about the procurement side: who to hire, what to watch for in quotes, and how to avoid the costs that show up on your P&L six months later.

I'm not an electrician or a plumber, so I won't pretend to know the best way to run conduit. But I can tell you how to vet a contractor, read a bid, and budget for the stuff nobody warns you about.

Step 1: Match the Unit to Your Actual Demand

This sounds basic, but I've seen it go wrong twice. Once with us, once with a colleague at another firm.

The Stiebel Eltron Tempra Plus comes in several flow rates (12 kW, 15 kW, 20 kW, 24 kW, 27 kW, 36 kW). The 20 kW unit handles about 3.5 GPM—enough for one shower plus a sink running simultaneously. The 36 kW does about 5.2 GPM—good for two showers or a shower and a dishwasher.

What to do:

• List every hot water point of use (sinks, showers, dishwashers, mop sinks) that might run at the same time.
• Calculate total GPM needed. A standard shower head puts out about 2.0 GPM. A kitchen faucet is about 1.5 GPM.
• Choose a model with enough capacity, but don't oversize. The cost difference between a 20 kW and a 36 kW unit is about $300-400 list price. But the electrical infrastructure difference—bigger breakers, thicker wire, maybe a panel upgrade—can be $2,000 or more.

Procurement tip: When you get quotes from vendors, ask for the price on two different models. One vendor quoted us a 36 kW unit when we only needed 20 kW. I'm not 100% sure, but I suspect they were upselling the more expensive install. Always match the unit to your actual peak demand, not what the contractor "recommends" without asking about your usage.

Step 2: Get Three Bids—But Make Them Quote the Same Scope

Over the past 6 years of tracking every invoice, I've found that comparing bids is useless if they're quoting different work.

For a Stiebel Eltron Tempra Plus tankless water heater installation, the scope should include:

• Mounting the unit on a wall (usually indoors, near the main water line).
• Running new dedicated electrical circuit (double-pole breaker, appropriate gauge wire per model specs).
• Connecting water supply lines (usually 3/4" copper or PEX with shutoff valves).
• Installing a pressure relief valve (required by code in most areas).
• Testing for leaks and proper temperature rise.

What I ask each bidder to include:

• Itemized labor cost.
• Cost of the unit (or mark-up if they supply it).
• Cost of materials (wire, breakers, pipe, fittings, valves).
• Permit fees (if required by your local municipality).
• Any fees for hauling away the old unit (if replacing a tank).

When we did our first install, Vendor B quoted $2,800. Vendor A quoted $3,200. I almost went with B until I calculated TCO: B charged $400 for "miscellaneous materials" (no breakdown), $200 for "permit handling" (which we later found out was just a trip to the county office—$45 fee), and $150 for "haul-away." Vendor A's $3,200 included everything. That's a 20% difference hidden in loosely defined line items.

Step 3: Verify Electrical Panel Capacity (Before You Sign)

This is the step most people overlook. I almost did.

A Tempra Plus 20 kW requires a 100-amp double-pole breaker. The 36 kW needs 150 amps. Most older commercial panels (200 amp service) can handle one 36 kW unit if nothing else in the building is running. But if you're adding it to a panel that's already feeding A/C, lights, and office equipment—you might need a panel upgrade or a sub-panel.

Here's what I do:

1. Ask the contractor to include a "panel capacity check" in their quote, or pay them for a separate trip to assess it.
2. If the panel needs upgrading, get a separate quote from an electrician for that work.
3. Factor that cost into your total project budget.

When we installed our second unit, the contractor told us "the panel should be fine." That 'should be' cost us an extra $700 when we discovered the panel was at 90% capacity already. We had to add a sub-panel. A straightforward inspection upfront would have cost $150 and saved us the rush fee to get it done in 2 days.

Step 4: Confirm the Warranty and Service Plan

Stiebel Eltron units come with a standard warranty (7 years on the heat exchanger, 3 years on parts). That's solid. But the warranty doesn't cover labor for repairs—just replacement parts.

What I negotiate in the contract:

• First year of labor included for any warranty-related callbacks.
• Discounted labor rate for subsequent years (post-warranty).
• Response time commitment (e.g., within 48 hours for a no-heat issue in winter).

I don't usually buy extended warranties. But for a tankless water heater, I make an exception—especially if the contractor offers a flat-rate annual service agreement. Our office pays $180/year for an annual flush and check-up. That's cheaper than calling someone emergency-style when sediment buildup causes a flow error code.

Step 5: Plan for the "Hidden" Costs

Every install has at least one. Here's what I track:

• Permit fees: $50 to $200 depending on your city. Some contractors include this, some don't.
• Old unit disposal: If you're replacing an electric tank, haul-away is $50-100. If it's a gas unit, disposal is more involved and can be $150-200.
• Gas line modification: If you're replacing a gas unit with an electric tankless (which many Stiebel Eltron customers do), you need to cap the gas line. That's a plumber or gas fitter right there: $200-400.
• Thermostatic mixing valve: Some code jurisdictions require one for tankless units if the water temperature exceeds 120°F. Adds $100-200 to the install.
• Condensate drain kit: If you live in a cold climate and the unit is in an unheated space, you might need a condensate drain heater or pump. Another $100-200.

When I audited our 2023 spending, I found that 14% of our "budget overruns" came from unplanned permit fees and disposal charges. We now ask every contractor to confirm whether they handle permits or if we need to get them separately.

Step 6: Ask About the Water Quality (Really)

I know, this sounds weird coming from a procurement guy. But here's the thing: tankless water heaters are sensitive to mineral buildup. Hard water scales up the heat exchanger faster. If your building has hard water (over 10 grains per gallon), you'll get a reduced flow rate and potentially error codes within a year.

What I check:

1. Request a water hardness test from your local utility or a home test kit (about $15).
2. If hardness is over 7 grains, plan for annual descaling of the unit.
3. If hardness is over 12 grains, consider a water softener for the whole building. That's a separate cost, but it extends the life of the water heater and every other appliance too.

Step 7: Schedule the Install During Off-Peak Hours

This is purely a procurement consideration. If your office or warehouse is operating during the install, you'll have water shutoffs and electrical outages. That means lost productivity. For our warehouse install, we scheduled it for a Saturday. The contractor charged a $200 weekend premium. But that saved us about $1,200 in lost labor cost from not having to shut down operations on a weekday.

Math:

• Weekday install: 12 hours for electrician + plumber = $1,500 labor + $800 lost productivity = $2,300 effective cost.
• Weekend install: $1,700 labor + $0 lost productivity = $1,700 effective cost.

Check your contractor's availability. Some offer evening or Saturday slots at standard rates if you're flexible.

Common Mistakes I've Seen (and Made)

1. Not securing the unit properly. The Tempra Plus weighs about 20 lbs empty (more with water). It needs to be mounted on a stud wall or using toggle bolts rated for the weight. Our first installer used drywall anchors for a 36 kW unit. It pulled out of the wall within a week. Don't ask.
2. Undersizing the electrical wire. The 36 kW model requires 3 AWG copper wire minimum. One electrician tried using 6 AWG to save money. That's a fire hazard. Always verify the wire gauge matches the manufacturer spec.
3. Skipping the pressure relief valve. Some contractors skip it to save $20. It's required by most codes and prevents catastrophic failure. If you see a quote without it, red flag.

After comparing 8 vendors over 3 months using our TCO spreadsheet, the one we chose wasn't the cheapest—but they were the most transparent about costs. That's worth something. I'd rather pay an extra $200 upfront than discover a $600 surprise later.

This checklist has saved us about $8,400 annually across our three units—largely by avoiding rushed decisions and unplanned upgrades. Your mileage may vary if you're dealing with different building configurations or local code requirements. But if you follow these steps, you'll at least know what you're getting into before you write the PO.