Office Heating Equipment FAQ: Vaillant Boilers, Heat Pumps, and the Stuff Nobody Tells You

I took over facilities ordering for our 85-person office in 2021. Before that, the closest I'd gotten to HVAC was adjusting the thermostat when people complained. Since then I've placed orders for two boiler replacements, one heat-pump upgrade, four ancillary heaters, and enough hot water heater maintenance calls that I have our plumber's cell number saved under "Emergency — Sort Of."

Here's what I've learned. The stuff I wish someone had told me before I signed the first purchase order.

Is a Vaillant combi boiler actually worth the premium?

Short answer: usually, with a caveat. We replaced a 14-year-old non-condensing unit with a Vaillant combi boiler in 2022. Installed cost was around $4,300 — roughly 15–20% more than the two other quotes we got from brands I'd heard of but couldn't tell you a thing about.

What we got for that premium: lower gas consumption (winter bills dropped about 18% the first year), fewer service calls, and — this is the part nobody mentions — a unit our contractor actually seemed to like working on. The guy who quoted the cheaper option told me, and I'm quoting here, "Vaillant's a good product, but we don't stock their parts, so if something fails you're waiting a week." That was a red flag I ignored at the time. Looking back, I should have asked how long that wait actually was — not whether it existed.

Bottom line: if the office plans to stay in the same building for five-plus years, the Vaillant premium pays for itself. If you're leasing short-term, you probably won't recoup it.

What does a Vaillant arotherm plus 15 kW install actually cost?

We got quotes for a Vaillant arotherm plus 15 kW in early 2024 when we were evaluating heat pumps for a 2,200 sq ft annex. Three contractors, all brand-authorized. The unit-plus-install quotes ranged from $5,800 to $7,200 — the spread came down to pipework and whether they were going to upgrade the electrical panel.

Here's the thing nobody tells you about heat-pump quotes: the number on the first page is basically a guess. Ours went up 22% once the electrician got into the wall and found the existing wiring wasn't rated for the load. If I could redo that decision, I'd have asked for a site-survey line item spelled out in the quote so I could see which assumptions were baked in. At the time, standard-practice quotes all looked the same, so I didn't push. My mistake.

If I remember correctly, the final installed number landed around $7,400. That felt like a lot for an annex (ugh), but the running costs beat the gas boiler it replaced, and we stopped paying for a separate AC unit in that space.

Lasko heater or diesel heater for a cold warehouse?

Different problem entirely. Our back warehouse — 1,200 sq ft, unheated, roll-up door — drops into the low 40s in January. The main HVAC doesn't reach it, and honestly, it shouldn't.

We started with a Lasko industrial shop heater. For an office manager, that's the no-brainer answer: plug it in, no fuel storage, no CO concerns, about $120. But it's also a space heater, not a heating system. It warms the immediate area and nothing else. If your warehouse crew is working in one corner, fine. If they're moving around, forget it.

We tried a diesel heater (torpedo-style, kerosene/diesel) after a brutal January. The difference is night and day — real heat output, the whole space comes up to temperature. If I remember right, the unit was $400-ish and we go through about $80 of diesel a winter. But you need ventilation, you need to think about CO, and you need someone who will actually remember to refill it. We designated one person. Even so, we've had "who used the last of the diesel" conversations I'd rather not repeat.

Realistically: Lasko for spot heat and safety, diesel when the space is genuinely occupied in winter. We ended up with both. No regrets on either — just wish I'd bought the diesel sooner instead of convincing myself a space heater would do the job.

How often do I actually need to drain a hot water heater?

Our plumber told me once a year. The doing it is about 20 minutes of work with a garden hose and a bucket. The reason to keep on top of it: sediment builds up at the bottom, and once it's bad enough the unit starts making a popping sound and you're looking at a replacement instead of a flush.

I'll be honest — we skipped a year. Nothing broke. But the plumber's comment when he finally drained it was not reassuring. Since then I've put it in the calendar alongside the boiler service. For how to drain a hot water heater, if you've never done it: kill the power or gas, close the cold-water inlet, attach a hose to the drain valve at the bottom, and let it run until the water comes out clear. There are YouTube videos that will do a better job than I can in a paragraph, but the point is — it's not a job you need to call someone for if you're comfortable around a hose and a valve.

How do I spot a vendor claiming to do "everything"?

This one took me longer than it should have. In early 2023 I got a pitch from a facilities-services company that claimed to handle HVAC, plumbing, electrical, and "energy optimization" — everything, basically. The contract looked clean. I almost signed.

The vendor who said "this isn't our strength — here's who does it better" earned my trust for everything else. I'd rather work with a specialist who knows their limits than a generalist who overpromises. When I asked the "everything" company which heat pumps they were authorized to service, they named three brands and missed the one we actually own. That was the deal-breaker.

So — quick test. Ask a potential vendor: "What's something you'd refer out to someone else?" If they say "nothing," they're either lying or they'll do a mediocre job on all of it. If they name two or three things without hesitating, they're probably solid for the rest.

The thing I wish I'd known before ordering

Installation is not a line item. It's a project. The Vaillant combi boiler install went smooth. The arotherm plus install had three separate scheduled visits that turned into five. The heating downtime was two days longer than promised (surprise, surprise).

If I could redo the heat-pump order, I'd have asked for a written project timeline with milestones in the purchase order — not the general "2–3 weeks" everyone gives you. And I'd have budgeted 10–15% over the quoted install cost for the inevitable "while we're in there" discoveries. That number seems to hold across every envelope of HVAC work we've done.

That's the FAQ. If I've missed something that's stressing you out, it's probably the thing I kicked myself over six months ago and never wrote down.