Can I run a Space Heater off one 400W panel?

Usually not continuously. With ~5 peak sun hours and ~20% system losses, most setups need around 5 × 400W panels for the daily energy shown.

What if it’s cloudy or winter?

Production drops. Add 20–30% extra panel capacity and consider a battery for cloudy stretches.

How Many Solar Panels for a Space Heater?

Rule-of-thumb estimate using typical wattage and usage hours. Fine‑tune with our calculators.

A typical Space Heater uses around 1500 W. If you run it for 5 h/day, that’s roughly 7.5 kWh/day. With about 5 peak sun hours and a realistic 20% system derate, you’d need approximately 5 × 400 W panels (≈ 1.88 kW of array).

👉 Try the Panel Sizing Calculator to plug in your exact sun hours and system losses.

Check battery & charging time

Battery Runtime Calculator — see how long a battery will run your Space Heater.
Charge Time Calculator — estimate how long your panels take to recharge.
Inverter Size Calculator — make sure your inverter handles startup and continuous load.

Quick math

Daily energy = watts × hours ÷ 1000 = 7.5 kWh
Array kW ≈ daily kWh ÷ (PSH × (1 − derate)) = 1.88 kW
400W panel count ≈ array W ÷ 400 = 5

Tips

Panels rarely output full nameplate — 70–80% in good sun is common.
Cold panels perform better; heat and clouds reduce output.
Angle panels toward the sun and keep them clean for best results.