Quick answer

Yes. Rainwater collection is fully legal in New Hampshire, with no state limits on how much you can collect from your roof.

What New Hampshire law says

New Hampshire places no state-level restrictions on residential rainwater harvesting. You can install as many barrels or cisterns as your property supports, and no permit or registration is required. No state restrictions. As always, check for HOA covenants or local ordinances before installing a larger system.

How much water a New Hampshire roof can collect

New Hampshire averages about 44 inches of rain per year. On a typical 1,200 square foot roof at 85% collection efficiency, that works out to roughly 27,900 gallons a year currently running into your storm drain. A single one-inch storm delivers about 635 gallons, enough to fill 13 standard 50-gallon barrels.

44"

Average annual rainfall in New Hampshire.

27,900

Gallons per year from a typical 1,200 sq ft roof.

$335

Approximate annual value at municipal water rates.

Your roof and rainfall will differ; run your exact numbers in the rainwater calculator.

The right setup for New Hampshire’s climate

At roughly 44 inches of rain a year, New Hampshire is a wet-climate state; your barrel will refill constantly. Prioritize a sealed, mosquito-proof design and plan the overflow path. A 50-gallon barrel with a diverter that returns excess water to the downspout is the right call.

Our pick for New Hampshire

Rain Wizard 50 + Diverter Kit, reviewed against our independent testing criteria. See all six models side by side.

Common questions

Is it illegal to collect rainwater in New Hampshire?
Yes. Rainwater collection is fully legal in New Hampshire, with no state limits on how much you can collect from your roof. This is educational information, not legal advice.
Do I need a permit for a rain barrel in New Hampshire?
No. New Hampshire requires no permit or registration for residential rainwater collection at any scale.
Does New Hampshire offer incentives for rainwater harvesting?
New Hampshire has no statewide incentive program at this time, but some utilities and municipalities offer local rain barrel rebates. Check with your water utility.

Sources

  1. Rainplan, 50-State Rainwater Collection Guide (2026)
  2. State statutes and water agency guidance for New Hampshire
  3. NOAA National Centers for Environmental Information, annual precipitation normals
  4. US EPA WaterSense, Outdoor Water Use fact sheet

Educational content, not legal advice. Laws change; confirm current rules with your state water agency.