The heaters we spec
into every greenhouse.

It comes down to three things: your structure size (width, length, peak height), your glazing type (single poly, double poly, polycarbonate), and your location. Our sizing wizard above runs the heat-loss math and gives you a specific model in about 60 seconds. If you want to talk it through, call us — we size heaters for greenhouses every day and a wrong-sized unit is a problem on your coldest night.

Most manufacturers advertise input BTU — the amount of fuel the heater burns per hour. What actually heats your greenhouse is output BTU: input × efficiency. The PTP series runs at 80% efficiency, so a PTP 400 consumes 400,000 BTU/hr and delivers 320,000 BTU/hr of usable heat. The Effinity PTC runs 93–97%, so nearly everything you burn becomes heat. Always size to output, not input.

The PTP is the right call for most operations: solid construction, 80% efficiency, 10-year heat exchanger warranty, and meaningfully less expensive. The Effinity PTC makes sense if you run year-round — the jump from 80% to 93–97% efficiency compounds into real money over a full heating season. If you are heating October through April every year, the PTC pays for the price difference. If you run a shorter season or have a tight budget, the PTP is the better value.

Yes — with the right model. The PTP is power-vented: combustion gases exhaust outside, but it draws combustion air from inside the space. That is fine for most greenhouse applications. The Effinity PTC has separated combustion: it draws fresh air from outside and vents combustion gases outside, so nothing from the burner enters your growing environment. For sensitive crops or tight sealed greenhouses, the PTC is the cleaner choice. The Hot Dawg draws combustion air from inside the space, so it is not recommended for enclosed greenhouses with plants.

Yes. Above 2,000 ft elevation, reduce rated output by 4% for every 1,000 ft. A PTP 400 at 4,000 ft delivers roughly 307,000 BTU/hr instead of 320,000. We carry the Modine High Elevation Conversion Kit to compensate. If you are above 5,000 ft, call us before ordering — you may need to size up.

All gas-fired models — PTP, Effinity PTC, and Hot Dawg — run on either natural gas or propane. Units ship configured for natural gas. Propane conversion is a field adjustment on most models. The HER series and Amp Dawg are electric — no gas required, no venting required. If you are on electric only, those are your options and they work well for the right size space.

Yes. Modine requires professional installation on all gas-fired models — doing it yourself voids the warranty. Gas connections, venting, and electrical hookups need a licensed HVAC technician. This is not a guideline, it is a warranty condition. Call us if you need help finding a qualified installer in your area.

All gas-fired Modine models — PTP, Effinity PTC, and Hot Dawg — carry a 10-year heat exchanger warranty and a 2-year parts warranty when installed by a licensed professional. The stainless steel heat exchanger option on the PTP extends corrosion resistance in high-humidity environments. The HER and Amp Dawg electric models carry a 2-year parts warranty.

The high elevation conversion kit adjusts the gas valve to compensate for thinner air above 2,000 ft, restoring output closer to the rated BTU. Below 2,000 ft you do not need it. Above 2,000 ft, order one with your heater. It fits all PTP, Effinity PTC, and Hot Dawg models.

Absolutely — this is what we do. Getting the size right matters: an undersized heater will not maintain temperature on your coldest night, and an oversized unit short-cycles and wears out faster. Run the sizing wizard above for a starting point, then call us to confirm before you order. Five minutes on the phone is a lot cheaper than buying the wrong heater.