Most greenhouses run perfectly well with neither power nor plumbing, and plenty of owners never add either. 🌱 But if there is any chance you will want them, the time to plan is before the base goes down, because a trench is cheap when the ground is already open and expensive once it is not.
Here is what each utility actually buys you, what it costs, what it triggers in permitting terms, and how to leave the door open without spending anything now. 🔌
💧 Water: the one almost everyone wants
Carrying watering cans is charming in April and grim by July, when a full greenhouse in hot weather wants attention every single day. 🪣
The options, cheapest first
- 🚿 A hose from an existing spigot. Free if the spigot is close. Fine for a season while you learn your habits.
- 🌧️ Gutters into a rain barrel: $80 to $200. A greenhouse roof sheds a surprising volume, rainwater suits most plants better than treated tap water, and it solves a drainage problem at the same time.
- 🚧 A dedicated frost-proof spigot near the structure: $50 to $200 if the plumbing run is short, considerably more if it is not.
- ⏲️ Drip irrigation on a timer: $80 to $250, and the single thing that makes a summer vacation possible without recruiting a neighbor.
💡 If you do only one of these, make it gutters into a rain barrel. It costs little, needs no trade, requires no permit, and it handles roof runoff that would otherwise soak the base you just built.
Frost is the constraint
Any buried water line has to sit below your local frost depth, which varies enormously across the country, or be designed to drain down each fall. A shallow line that freezes and splits is a spring excavation nobody enjoys. Ask your plumber or building department for the local figure. ❄️
⚡ Electricity: think hard about whether you need it
Power opens up real capability, and it is also the utility that most often gets installed and then barely used. 🔌
What it genuinely enables
- 💨 Circulation fans, which reduce fungal problems and even out temperature far more than people expect for the cost.
- 🌱 Heat mats and propagation domes, which are the most efficient heating in a greenhouse because they warm the root zone rather than the air.
- 💡 Lighting, which mainly extends when you can work rather than how plants grow.
- 🔥 Space heating, if you intend to hold temperature through winter.
- ⏲️ Timers and automation for irrigation and vents.
What it does not require
Ventilation. This is worth stating plainly because it is the one function people assume needs power. Automatic vent openers work on a wax cylinder that expands with heat, need no electricity at all, and cost $30 to $70 per vent. They are the highest-return purchase in the entire greenhouse and they run on sunshine. ⚙️
📜 The permitting reality
This is the section that changes plans, so it goes here rather than at the end. ⚠️
Running electricity or water to an outbuilding almost always triggers a permit of its own, regardless of the structure's size. A greenhouse that needed no building permit because it sits under the footprint threshold can still require an electrical or plumbing permit the moment a cable or a pipe crosses the yard.
What that involves, typically:
- 🔌 Electrical: a permit, work by or inspected against code, correct burial depth, conduit or direct-burial rated cable, GFCI protection, and usually a small subpanel or a dedicated circuit. Damp, earthy, metal-framed buildings are treated as a demanding environment for good reason.
- 🚰 Plumbing: a permit, correct depth below frost line, a backflow prevention device on any irrigation connection, and an isolation valve so you can shut it down for winter.
📞 Raise both on the same call you make about the structure itself. We listed the questions worth asking in our permits guide, and "am I likely to add power or water later" belongs on it even if the answer today is no.
🧱 Why sequencing saves real money
The trench is the cost, not the cable. 💰
If you are already excavating for a base, adding a trench alongside it is incremental work. If you decide two years later, you are cutting through established lawn, possibly through a paved path, and paying for the whole excavation as a standalone job. The base decision itself is in what foundation does a greenhouse need.
The cheap insurance, if you are undecided: lay an empty conduit while the ground is open. A run of plastic duct with a draw string costs very little, needs no permit on its own because nothing is energized, and turns a future installation into pulling a cable rather than digging a trench. 🧵
💡 Run separate ducts for power and water rather than sharing one, keep them a sensible distance apart, and photograph the route before backfilling. A photo with a tape measure in it is worth a great deal in five years.
🌞 The alternatives worth considering first
Before committing to a trench, check whether these cover what you actually need: 🔋
- ⚙️ Automatic vent openers for ventilation, no power required.
- ☀️ Solar-powered fans and lights, adequate for circulation and working light, not adequate for heating.
- 🔋 Battery-powered propagation domes and rechargeable lights for occasional propagation.
- 🛢️ Thermal mass instead of heating: black water barrels, bubble insulation on the north face and a frost cloth tunnel inside typically buy five to ten degrees for a one-time cost under $150, with no utility at all.
- 🌧️ Rainwater harvesting instead of a spigot.
For a large share of owners, that list covers everything they would have used power and water for, at a fraction of the cost and with no paperwork. 🤝
🧮 What heating actually costs, if that is the plan
Worth pricing before you trench, because it is often the deciding number. ⚡
Holding a 100 sq ft greenhouse just above freezing through a cold winter runs roughly $40 to $120 a month in electricity, varying enormously with climate, glazing and local rates. Holding it at tomato temperatures runs several times that, and for nearly every home grower exceeds the value of the harvest.
Which is why glazing choice matters more than the heater. A well insulated structure costs meaningfully less to hold at temperature. 🌡️
❓ FAQ: greenhouse utilities
Do I need electricity in a greenhouse?
No. Most owners run without it. Ventilation, the one genuinely essential function, is handled by wax-cylinder openers that need no power at all. ⚙️
Can I run an extension cord instead?
Only temporarily, for a specific task, with an outdoor-rated cord and a GFCI. A permanent extension cord to an outbuilding is a genuine hazard in a damp, metal-framed environment and is not a substitute for a proper circuit. ⚠️
Does adding power need a permit?
Almost always, regardless of the greenhouse's size, and the same is generally true of a buried water line. Ask about both on the same call you make about the structure. 📜
How deep does a water line need to be?
Below your local frost depth, which varies widely across the country. Your building department or a local plumber holds the figure. The alternative is a line designed to drain down each fall. ❄️
Is rainwater good enough for a greenhouse?
Better than good enough. Most plants prefer it to treated tap water, a greenhouse roof collects a substantial volume, and it costs a fraction of a plumbed supply. 🌧️
What if I am not sure yet?
Lay empty conduit while the ground is open. It costs very little, needs no permit on its own, and converts a future trench into a cable pull. 🧵
🌿 The decision, simplified
Assume you will need neither. Fit automatic vent openers and gutters into a rain barrel, which cover the two functions that genuinely matter. Then, while the ground is open for the base, lay empty conduit so the option stays available. 🧭
That approach costs almost nothing today and removes the expensive version of this decision entirely.
An automatic vent opener is where we would start, and every structure in the Prime Greenhouses range publishes its vent configuration alongside footprint and ratings, so you can see how much passive ventilation you already have before deciding whether power adds anything. 📊