Questions on heatpumps vs. electric baseboard and an a/c question (for small room)
I work from home, and have an office that’s about 20′ X 8′. It’s a converted front porch, that does have some fiberglass insulation, but with a lot of window light (five 4X4 double-pane sliders — about 80 square feet of glass, plus an exterior door). It is northeast facing.
There is no a/c out here, but I need it. July and August get unworkable. The heat in the porch is electric baseboard (4 baseboard units). This is in the NE US, with the heating season running Oct – April, and sometimes it can get to below freezing outside, especially Dec – Feb.
For the downstairs part of the main house, we are looking at installing a ducted a/c solution (the Mrs. says no to ductless mini splits). While we are doing that, I want to solve the a/c need for my office, too. But, my office has a really different eco system then the rest of the house. I am therefore thinking of putting it on it’s own a/c.
I need quiet as I spend a lot of time on the phone, so I’m thinking a ductless mini split, but it’s a lot of money for one room.
If I put in a heat pump ductless unit for a/c, would I get any ROI on using the system for heat over my electric baseboard? If there’s a good ROI on it, it might help justify the cost of the mini-duct system. If there is no ROI (or if it’s a 10 or 15 year return), then that becomes less attractive than just running a single a/c duct to the office, and putting up with the oddities of being off-zone. Another option is a fan in the doorway, but I want to be able to shut the kids out so I can work.
Any help, pointers, general impressions or links to on-line calcuators is much appreciated.
Replies
A heat pump is roughly 3-5 times more efficient than resistance heating in your environment. However, in most situations you tend to need a larger heat pump for heating than you need for cooling, so to "balance" the size of the unit better it's sometimes best to use both heat pump and resistance heating.
A lot of electric utilities, etc, have online calculators that will allow you to estimate the operating cost of the heat pump. But of course you also need to figure in up-front cost and maintenance/depreciation costs.
My 2cents
I believe mini-splits cost about $1500 installed after a lot of incentives (in my NW region). For that money, you could buy a lot of insulation. If you have an infrared thermometer (about $50, I use Ryobi), you can verify where your cold spots are. I'm betting the roof and the floor are both poorly insulated.
Of course, the better insulated the space is, the less you'll spend on A/C and heat. So your ROI will change. If you need, for example, 5,000 BTU/hr in winter to heat it as it is (a wild guess), then your higher energy costs will drive you towards a more efficient system in order to keep costs down. If, however, your space stayed cool in the summer until, say, 2 PM, would a high quality window a/c unit be acceptable?
You might try asking the same question on the Green Building Advisor boards. They have some tremendous resources toward answering your question.