Quick question…we’ve just got a heat pump and we’re not sure whether to just run it off the grid or use up the cheap juice in the battery? We’re on IOG with gen 1 5kw, 9.5 battery, 6.24 east/west panels and a Tesla. Pre heat pump we were in negative bills. Any thoughts?
SimonClarke if you didn't use the energy from the battery, what would you do with it instead?
Export only earns 15p, whereas daytime import is around 23p.
How much use does Tesla get? I'm in a similar position and am considering switch from IOG to cosy (maybe agile), but I don't use EV all that much, so heating costs are likely to dwarf EV costs.
DD we do about 10k miles so it is a noticeable amount. We currently fully charge the battery and export solar and do a 2 hour timed export. We very rarely run out for at least 6 months of the year and time shift what we can in the winter. IOG day rate here is 0.2439 so we are trying to understand what is for the best now with the ashp. It will heat water on the 7p rate so it is just the heating. I think the oil worked out to be 8500kw input for heating only which would have cost approximately £550 so the ASHP would be about £700 for the same at a cop of 3 (hoping for better).
We run two heat pumps with an A2A set up and 19kwh of batteries. Batteries, charged on IOG, keep us going on all but the 4 or 5 coldest days of the year - for those it's more cost effective to run the gas boiler which we also use for hot water. However, A2A allows us to heat selectively and very efficiently so we don't heat all rooms all the time. Plus we have an A rating for the energy efficiency of the house. If you are using an A2W system, you will likely use a lot more than this due to the "always on" operation. The first year of use is one of discovery for sure. There is also the Octopus Cosy tariff which now has triple dip at low rates which may be worth a look. Given the tail off in the last 10% of charging on the newer battery firmwares, that's something we may also need to look at. Good luck with it.
I realise that the battery can’t supply enough power in the winter but just wondered if anyone had found an advantage in saving it for the house use rather than ashp using it all or if there was any saving in using it for the ashp. We always ran the oil boiler 24 hours as once up and running there was not much difference
SimonClarke Electricity is electricity - I can't think of a reason to distinguish using it for heating or something else. The only case for saving battery is if your tariff has a particularly expensive period (eg 4pm to 7pm).
I'd say it was better to use the battery than to save it - if you end up not using it all, you've lost out.
Best way to run the heat pump is low and slow, on all the time at a constant (weather compensated) temperature so that the heat pump supplies enough heat to replace heat lost on a continual basis. This’ll give you a warm and comfortable house and the least electricity usage from the heat pump.
If you are on IOG then no point in saving the battery for ‘later’ as it’s a flat rate during the day. Other tariffs may be better but you’ll need to understand your daily ASHP, home and car consumption to figure out what is best for you.
For me my ASHP uses more than my battery so I wanted the cheapest way of buying electricity and went for Agile for last winter. I’ll check the figures again for the new 3-period Cosy tariff but likely I’ll stay on agile.
We are going to stick with IOG for the moment and run the heat pump from the battery and grid and see how it goes. We always ran the oil on 24/7 as we have done comparisons between using it on timer or full time and there was little difference except that the house is more comfortable on full time. We’ll just use the heat pump in the same way.