Brian When I first installed my greenhouse I had placed black plastic 5 gallon pails with lids along the south facing edge under the benches. Each held 5 gallons of water. It is calculated that for every one degree F rise in the water in the pails it represented 8 BTU's. So each 5 gallon pail would hold 45 BTU's for every one degree rise in temperature. At night was the exterior temperature dropped the heat would radiate to the greenhouse away from the pails. With our lows here in dead of winter at 8-11 F it was enough to keep the greenhouse at a minimum of 42-45 F. Arnold -----Original Message----- From: Brian Whyer via pbs <pbs@lists.pacificbulbsociety.net> To: Pacific Bulb Society <pbs@lists.pacificbulbsociety.net> Cc: Brian Whyer <brian.whyer@btinternet.com> Sent: Mon, Nov 1, 2021 6:06 am Subject: Re: [pbs] Greenhouse Heater Issue I am using a 30/40 year old electric fan heater (permanently on) to keep my 8'x8' greenhouse at 6C min. On it's second thermostat now. Oil the bearing every few years ;-) High iron content brick storage heaters were popular for "central" heating here some years back. Powered at night only. Greenhouses with pit type concrete filled "underfloor" storage was suggested here, with a fan circulating 24 hours. Storing during the day, releasing at night. A contact had a large-ish pond under his staging for the same purpose. Full of frogs when I last saw it. I have 2 water butts inside that get warm to the touch in summer. Looked at solar power and ground source when this house was built. Too long a repayment time unfortunately, and poor roof exposure for panels. Brian Whyer SE UK no frosts, yet. Does anyone use a solar powered greenhouse heater? _______________________________________________ pbs mailing list pbs@lists.pacificbulbsociety.net http://lists.pacificbulbsociety.net/cgi-bin/… Unsubscribe: <mailto:pbs-unsubscribe@lists.pacificbulbsociety.net> _______________________________________________ pbs mailing list pbs@lists.pacificbulbsociety.net http://lists.pacificbulbsociety.net/cgi-bin/… Unsubscribe: <mailto:pbs-unsubscribe@lists.pacificbulbsociety.net>