solar hot water backup

[antonvanduuren]

Anyone have experience with using a propane tankless hot water heater as backup for a primary solar DHW system? Is there a best model to look for, for example, one with a low BTU kick-in to allow the tankless to minimally boost the solar water? Are electric tankless heaters better than gas for this purpose?
Thanks.

[SolarGary]

Hi,
I've not had direct experience with this, but have been told that its a good way to go.

As you say, you need one that can modulate the flame so it only adds as much heat as is needed. I know that at least one of the Bosch ones does this -- they mention boosting water for solar water heating. I think its the one with a "B" in the model number.
I believe that Takagi also makes one that modulates the flame -- they have a good reputation.

Gary