Is the electric rate the same for your previous home and new home?

What fuel did you use in each house for heating?

Is the circulation of the radiant hot water constantly running?

Your general location please.

What is the living area size of the lower level?

Is lower level at or partially elbow grade?

15 KW equals about 51 KBTUs, not an insignificant amount.

Is this actually a new home, new construction?

Home is all electric? What is your electric rate?

What size home overall?

How do you heat other area of home?

Post example of recent electric bill, both KWHs and total amount.

IMO

Well some of the important information is missing like the living area size of lower level or the continuity of the circulation. It could not be the only reason. A bit from other appliances must be adding, as it is a new home it should have some different appliances.

In answer to some of the questions:

Electric rate is the same and the square footage of the home is the same - 3200 square feet.
Living size of the lower level is about 1600 square feet, the same as in our old home.
The lower level in the old home was a full basement (entirely below grade), the new home has a walkout basement.
Heating is irrelevant - our furnace was gas in the old home and is gas in the new. Our new home is about 20 miles from our old home; thus, our location is irrelevant. Additionally, the increase in our electric bill began when we moved in this summer, before we needed to heat the home.
The new home is new construction.
We have the same type of appliances in the new home (e.g., washer, dryer, range, microwave, water softener, refrigerator, air exchanger, and TVs). They are supposedly more energy efficient than in our old home. One difference is that the water heater in the new home is electric while it was gas in the old home; the increase cost of an electric water heater should not be $300 a month, which is the amount that our new electric bill increased.
We had four bathrooms in the old home, while the new home has three, but there are only two of us living in the home.
The way that in floor radiant heat works is that a boiler heats water which is always circulating through pipes installed in a concrete subfloor.

You said that the boiler for the floor heat is electric, and 15kw. If it runs for an hour, that's 15kwH. If your electric rate is $0.15/kwh, that's $2.25/hr or $54/day or $1620/month.

A duty cycle (ratio of time on to time off) of %20 would still be $324/month.

It makes no sense to have an electric hot water heater when you are using gas for your boiler.

Do you have a 75 gallon hot water heater? You are using a fair amount of electricity just to maintain the water temperature. What temperature have you set for the hot water heater?

"Our new home is about 20 miles from our old home; thus, our location is irrelevant."

no one wants to know your address, but location is relevent. different winter needs in different parts of the
country.

are efficiencies of gas furnaces & size the same?
age of gas furnaces the same?
(as in previous house 20 miles away)

what size water heater & age?
elements in water heaters go out and
can cause increases in utility costs.

best of luck.

If your summer cooling bills immediately went way higher; I would suspect a leak from the attic or garage, or some unconditioned area into the Return-Air to the blower chamber.

That unconditioned air can be very hot in summer & very cold in the winter which would run your bills way-up.

During the hot days in summer, you should have been checking the indoor humidity level along with the supply-air & return-air temps, & the temp-rise off the outdoor condenser. Those checks will tell you/us what the problem is apt to be.

Now, in winter you can check the run-time of the furnace burner, then the time when it restarts; divide the time between starts into the Burner-Run-Time, then multiple that percentage by the OUTPUT Btu/hr of the furnace.

Also, check the temp-rise above the return-air-temp; multiple the temp-rise by 1.08 & divide that number into the Btuh Output of the furnace to get the CFM airflow of the blower.

Then Do a Free load-calc on your home...compare the results to what your furnace, during the coldest days/nights shows you are using; probably at a higher temp than the winter design used by the calc.

Here is a link that might be useful: Free Online whole house load-calc

Thanks for the ideas on what to check. Why check out the furnace? It is gas, and we have no problem with our gas bills.

You said your summer electric bills were high when cooling your home...therefore A/C & air flow has to be checked.

You can check air flow CFM in heating mode of furnace.

OK, so only the blower is using electrical power.

If you have an A/C condenser, then in the summer when the A/C runs the condenser uses a lot of electricity!

In the winter in heating mode then mainly only the blower motor uses electricity...

And one more time, I want to be clear. You said you have an ELECTRIC boiler/hot water heater circulating water to your basement floor. You stated it was 15kw/62.5A. That's pretty big for a hot water heater.

We are wondering if the culprit is the hot-water circulating in-floor radiant heat in the lower level, a feature our previous home did not have. Is that likely? (The heater is rated at 15Kw and 62.5 amps, whatever that means.) As was stated another previous reply, it means that the in-floor heating system uses 15,000 watts (15kW) of power for every hour it runs.

The electric company bills for kWh of power used ... kilowatt hour ... which is 1,000 watts of power consumed for a time period of 1 hour.

500 watts (five 100-watt light bulbs) running for an hour is half a kWh. Two hours (500 x 2 = 1,000) is one kWh.

Your radiant heater is equivalent to 150 100-watt light bulbs.
It consumes 15kWh (15,000 watts / 1,000-hour = 15kWh

A typical electric clothes dryer is 5,400 to 5,600 watts.
So your radiant floor heat is also equivalent to approx 2.7 electric clothes dryers.

Amperage (amps) is a measurement unit of electric power.
Amps and volts.
Amps X volts = wattage.
62.5 amps x 240 volts = 15,000 watts, or 15kW

You can calculate the effective rate you pay for electric power by getting the kWh used for the billing period and $-amount billed from your last electric bill.
$-amount billed / kWh used = kWh rate billed

kWh rate X 15 = how much your radiant floor heater costs for every hour of continuous run time. Of course, it may not run 100% of the time ... presumably the heating element(s) cycle on/off to maintain a target temperature on the circulating water. Don't forget the pump motor is also part of the cost, which may or may not be included in the 15kW figure.

I agree with last post.

Unless there are malfunctioning appliances, everything points toward the electric boiler for downstairs radiant heat as the culprit.

2 questions must be answered.

Is the boiler working properly?

And if so, is it sized correctly for the jobs it is intended to perform?

IMO

Great help. I suspect, too, it is the in floor radiant heat. We're contacting the installer to have it checked.

Regarding the summer & heating bills, my point was there was no difference between summer and winter...they are both high!

Thanks again.

I still think the hot water heater is playing a role in this. Did you check the size of the tank?

You may be right about the water heater. It is a 50 gallon, which is the same size as the one in our last home, only that one was a gas heater. There are just two of us, so it may be sized OK, but in the old home we didn't run out of hot water and here we have a couple times.

I still think the hot water heater is playing a role in this. Did you check the size of the tank?

electric 50 gallon water heater Mike_Home.

as I alway start with cheapest thing to fix first
I'd be making sure both elements worked and
not just one element heating the water..
which would cause the hot water to run out sooner.

Two people should not be running out of hot water with a 50 gallon hot water tank. It sounds like the tank is not running efficiently.

I would recommend replacing it with a 40 gallon gas fired model with a 40,000 BTU input. That should be plenty for two people. The shower heads should be the low flow type. They allow you to take a long hot shower without draining the tank.