Indirect water tank

depends on your relative cost of gas and electricity. unless you are using a ton of hot water i kind of doubt that the hot water is the source of your high electricity usage.

What is your electric rate $ per kWh? Time of use?

gas rate? $ per therm?

How many gal is your current electric tank? do you ever run out of hot water?

so you have about 120,000 for DHW production. With a plate HX assembly you get 3 gpm at a 77 degree rise

Incoming water at 43 to 120F for example

Here is a fuel cost calc

Use electricity at 100%, gas at 87%

https://coalpail.com/fuel-comparison-calculator-home-heating

Your GV90+ boiler operates at a lower cost per BTU than the oil boiler it replaced. Am I correct that the old oil boiler used a tankless coil for DHW, which proved problematic, leading to the addition of an electric water heater in 2021?

Most of your savings from switching to gas come from the GV90+ being a cold-start boiler. The old oil boiler likely maintained a minimum temperature for DHW even when hot water wasn’t being used. When a separate water heater is added, the oil boiler is often not converted to cold-start, so it continues wasting energy. Now you are using electricity—the most expensive fuel—to maintain DHW temperature.

I believe an indirect water heater would be a better solution. It’s a dedicated, well-insulated tank with no vent connection, reducing standby heat loss, and it uses the more efficient gas boiler as its heat source. An indirect tank can typically hold hot water for 16–20 hours with minimal temperature drop before needing to recover, whereas electric and vented gas or oil water heaters lose heat more quickly and often reheat every 4–5 hours.

In my opinion, based on over 40 years of oil and gas service and installation experience, indirect water heaters are the most efficient and reliable way to produce and store domestic hot water. Unless you are like @ethicalpaul and decide to install a heat pump electric water heater. I guess that will cost about the same as the Indirect job, but I'm not sure how long those tanks last. I don't believe that they have a lifetime tank warranty like my indirect does.

The answer is no, an indirect is not a good option. If you think your electric bills are high, wait until you see the parts and labor to install an indirect.

And plus, I strongly doubt that your electric bill woes are due to your 40 gallon water heater. The cost to run that should be in the $600/year range.

But if that is more than you want to spend, you should look at a heat pump water heater. You may have incentives to install one from your state or utility or both, and they are almost free to run.

if you use an indirect or a hydrobooster, you need to size it such that it mostly just runs with big loads, it doesn't fire the boiler 10x a day just for hand washing and losses because although the boiler is maybe 20% more efficient at putting the energy in the water, the boiler has significant standby losses every time it starts and stops and that will quickly eat up your gains over a direct fired or electric water heater if it happens a lot.

Here are a few options EK still offers with explanations on how they work.

Yes, these kits are still valid part numbers. I'm not exactly sure when we first offered them but I found a cut sheet dated from 2000. The modified dip tube is a key feature when converting an electric tank for storage and we actually sell them as a replacement part.

@szwedj with a modified dip tube can they still be used in electric mode as backup?

@szwedj Would running the hot water in at the t&p valve get the same effect as modifying the dip tube?