Re: efficiency of electric furnaces.... new vrs old
Hello ndemge - you've certainly got a number of opinons but let me set you straight.<br /><br />ALL eletric heat old or new has a COP of 1. (well talk about COP in a minute.) That means it's a 100% effiecient - no loss from mechanical sources, friction etc. OLD or NEW you will see NO savings ever in cost of opperation with some VERY minor caveats. Remember your stat cycles on temp - I promise you, whether you have a 5 KW strip run for 1 hr to heat yor home or a 10KW for 1/2 hr - the KW consumption is the same. Temperature rise is the only differance -- more strips - more temp rise or better quality heat form your vents.<br /><br />Newer electric furnaces have some control features that can help in a very very small way by stageing the heat strips & allowing the blower to stay on a 30-90 seconds after the heat cycles off -- this improves life expectancy of the strips from heat fatigue & delivers a couple of BTUs vertually for free if the furnace is outside of the conditioned space -- if it's in the conditioned space - no savings is appreciated. Newer furnaces can also employ ECM motors that use less electricity - but this is not a varible of the heat source. Keep in mind the Florida Solar Energy center has vaidated the biggest energy loss in homes is duct loss / gain, either leaking ducts or ducts that are picking up cold or heat from the attic. As a rule, contractors have to add 15% capacity just to overcome this loss issue -- (so next home desigh the ducts IN the living space)<br /><br />Lets address your A/C 1st --- if you changed your outdoor unit (the condensing unit) w/o changeing the indoor coil (the evaporator) you did yourself a huge injustice. While systems can be made to run, you'll never have the enginnered performance of the A/C without matching the coil. So if & when you're ready to change the indoor unit --- go to ARI.org w/ your model # from your new cond. - you'll find every rated unit that is approved to run w/ your unit the BTUs & the SEER.<br /><br />I know I'm too late w/ this news flash -- but heres a big heads up. The DOE has changed Federal Law that mandates 1/06 all manufactures produce no less than 13 SEER (Effiecnacy)- this absolutly mandates you change the indoor & outdoor system as old metering devices just wo'nt work with a new 13 SEER condensor. And if life just was'nt intresting enough.... in 5 short years (1/2010) the EPA has mandated that the freon we use today will be phased out of production..... this will make for a whole new set of issues as NO old refriferant (R22) & new refrigearnt (R410A) is compatable. Just call me Mr Sunshine.<br /><br />Now heat pumps --- here's the FACTS:<br /><br />All heat pumps (assuming they are installed properly, charged properly and have the control systems set up properly will outperform ALL electric heat systems - for HEAT, not necessarly the A/C side. At least to the balance point and most down to 10 degrees.<br /><br />Perfromamce of heat pumps in measured in COP (Coeffiecient of Perfromance) the worst heat pump made has a COP of 3.5.... in other words it WILL deliver 3.5 times more BTUs of heat for the exact KW consumed - some go well up to 5+ COP.<br /><br />Now this is the important part - All heat pumps drop in perfromance when it gets cold - funky huh - just when you need more heat the worst - it starts falling off in performace - but thats how it is unless you go geothermal. Various parts of the country employ heat pumps differnly, IE in some areas a heat pump is used until the ambiant temp drops to 30-18 degrees (the balance point) then switch over to gas, oil or strip heat. A lot of varibles need to be addressed IE ultility rebates, KW cost, Gas cost, initial investment etc.<br /><br />From a pure service prespective.... heat pumps are not the chosen favorite of most mechanics. It's a fact they do have more moveing parts, have more controls (defrost etc) and don't enjoy the terrific temp rise that is enjoyed by gas & oil heat in terms of quality heat. I would strongly suggest that if you go heat pump ask for the extended warranty.<br /><br />I'd also like to mention - before you go to far down this road - spend a few extra dollars on a quality air filtration system (Aprileaire 2200 / 2400) to protect the new equip & your family.<br /><br />Be sure to get 3 bids, ask for referrals, mandate the contractor pull a permit & don't let them start until a CURRENT workers comp & liability insurance certificate is in your hands - this won't offend a legitamate contractor - if this offends sombody tell them to pack salt. - do not go low bid.<br /><br />PS - have them put in writting that your duct work has a max statis pressure of .5" - let them show you with a manometer.<br /><br /><br />Got any questions I did'nt cover?<br /><br />Dave B.
