[RE-wrenches] Electric boiler usage?

[Ian Woofenden]

Hi Jesse,

If your client were mine, I'd be recommending a heat pump, which 
would lower the electrical load significantly. It will be a larger 
up-front investment, but will likely have a positive economic return, 
and an immediate reduction in grid fossil fuel use. Whether 
air-source or ground-source would depend on the climate and budget. 
If they were willing to let go of the radiant floor delivery system, 
a couple of mini-splits might do the job (depending on the climate). 
An HVAC contractor I work with recently speced a single mini-split 
for a 1,000 sf home in our moderate climate -- installed cost was 
$1,000. I'm putting a kWh meter on it, so someday I'll have data.

I strongly recommend that you have your client add a reconditioned 
kWh meter (available for less than $50 from a couple of sources), so 
that they have a measure of actual ongoing performance of whatever 
heating system they decide on.

Projecting your electrical usage for boiler or heat pump will be 
tricky, since it will be based on your heating degree days and the 
overall R-value of your house. Local heating contractors _should_ be 
able to give you an estimate based on generalized tables. Sometimes 
they only work in dollars, but converting to kWh is easy. But I don't 
think their estimate will be specific to the heat gain/loss of that 
specific house, but just based on an average and the cubic footage.

I'll be interested to see what decisions are made and how it plays out.

Ian

>Wrenches,
>
>I am working with a family that wants to install a grid tied system 
>that will offset, as close as possible, 100% of it's electrical 
>usage.  We have calculated for almost all the loads except the 
>electric boiler. 
>
>  Problem, they don't know which boiler they will be using. The home 
>will be 1800sq ft, it will have the in floor heat between the floor 
>joists and the joists will then be insulated with foil-faced 
>insulation. 
>
>Has anyone calculated a boiler like this out for annual electrical usage?
>
>
>Thanks as always,
>
>Jesse

-- 
Ian Woofenden <ian.woofenden at homepower.com>, Senior Editor, Home Power magazine
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