Most efficient way to use solar?

YorkshireJames

I'd really value some help. We've just moved and bought a property with a 'C' energy efficiency rating, with solar panels, solar hot water, and a ground source heat pump.

Because of that, I thought the new house would be a lot cheaper on energy than our old house which was 'F' on the efficiency scale, 20% bigger, and had no solar or ground source. Even talking into account the 54% price hike, the estimated bill we have been given for the new house is 10% higher than our old house.

Was I being overly optimistic? Will solar power, solar heating, and a ground source heat pump not actually save us any money on our energy usage? Have I been sucked in by the hype? Also, are there any tips for using these systems more effectively to save money?

Second question, we're now on a feed in tariff. What's the best way to maximise income from that? Is it the same across all suppliers? 

Petriix

The first thing you can do is ensure that you have clear monitoring to show you exactly how the energy is flowing: how much the panels are generating, what's being used in the house and how much is flowing from/to the grid. If nothing else, a smart meter IHD will show you when you're importing, and some show export.

The trick with utilising solar is to try to match your usage with your immediate generation. That means running appliances in series and getting to know when they use the heating element in their cycles.

You can just about decipher from my usage today (below, recorded by my Zappi EVSE) that the three purple spikes on the lower graph are when the washing machine then dishwasher used their heating elements. Because I'm familiar with the cycles, I know that the washing machine is only heating for a short period at the start so I can switch both on at the same time.

We were out for 3 hours so couldn't put the dryer on until a little after 1pm and we ended up exporting much of the peak generation, but timed it perfectly so that the washing was dry before the sun moved too far round. The blue is the car charging, which will start automatically whenever there's sufficient surplus, as long as it's plugged in and the house isn't using too much.

I go so far as to pause the dryer to boil the kettle to avoid importing unnecessarily (when I get my battery fitted then I'll be able to worry less about such things). Unfortunately, with a heat pump, you can't really turn it on and off with the sunshine. But, if you become familiar with how much power it draws and when, you'll be able to minimise your imports as much as possible.

Definitely look at getting onto a tariff with a cheap off-peak rate. And once you understand your usage, look at adding some batteries to help minimise how much peak rate electricity you need to import. You mentioned FIT. If you are on actual FIT payments (not the SEG which replaced the older scheme) then you're almost certainly on deemed export payments which means that you can use everything you generate without penalty.

Thrugelmir

How often does the sun shine when you need your heating on? 

YorkshireJames

Wow, that's really helpful. Thank you.

We're on economy 7 with Scottish Power. Never had a smart meter before but you graph looks really helpful. Can I just ask for a smart meter? Are they all as good as the Zappi EVSE? Any recommendations?

Verdigris

EPC's, generally, aren't worth the pixels they're displayed on. Having said that, you should be an A rating on that set-up.

When you say "new", do you mean newly built? If so, it sounds like your GSHP is not set up properly, for a start. It should be costing on a par with gas central heating.

Is it underfloor heating or radiators? Do you know what the flow temperature of the system is?

The solar PV may not have helped you too much as the output is lowest when you need it most for the heat pump. The addition of a battery, and going on a Time of Use (TOU) tariff may be helpful.

Water heating can markedly reduce the efficiency of a heat pump system, but I assume the solar thermal is supposed to overcome that. Sadly, in the winter, it will only make a marginal difference. In the summer, it will probably meet most of your needs. The GSHP should be set to raise the hot water to 50 degrees, most of the time, and only up to 60 degrees, once a week, to mitigate any legionella risk.

When you say "feed-in tariff", I'm assuming that is a SEG, if it is a new house. You may want to investigate Octopus's Agile tariffs, which are currently giving good returns. If you have an EV the Octoipus Go tariffs may suit you better.

QrizB

YorkshireJames said:

I'd really value some help. We've just moved and bought a property with a 'C' energy efficiency rating, with solar panels, solar hot water, and a ground source heat pump.

Because of that, I thought the new house would be a lot cheaper on energy than our old house which was 'F' on the efficiency scale, 20% bigger, and had no solar or ground source. Even talking into account the 54% price hike, the estimated bill we have been given for the new house is 10% higher than our old house.

Was I being overly optimistic? Will solar power, solar heating, and a ground source heat pump not actually save us any money on our energy usage? Have I been sucked in by the hype? Also, are there any tips for using these systems more effectively to save money?

Second question, we're now on a feed in tariff. What's the best way to maximise income from that? Is it the same across all suppliers? 

Petriix has given you some good advice on how to optimise your solar PV system (the Zappi EVSE is an electric car charger, and quite an expensive one at that, but you will get some information from a smart meter).

If you want to get into the nitty-gritty of optimising your heat pump, you could do a lot worse than read this thread.

Petriix

YorkshireJames said:

Wow, that's really helpful. Thank you.

We're on economy 7 with Scottish Power. Never had a smart meter before but you graph looks really helpful. Can I just ask for a smart meter? Are they all as good as the Zappi EVSE? Any recommendations?

EVSE = Electric Vehicle Supply Equipment (an electric car charging point). The Zappi needs to monitor solar generation and grid use to divert the surplus solar to the car; as a byproduct it records clear data and shows near-real-time usage via its app.

My smart meter IHD simply shows how much I'm importing at any given moment. The half-hourly readings show exactly what I'm being billed for, but are only available the next day via the Bright app or on my Octopus account.

There are various other solar energy monitors depending on your equipment.

Verdigris

If you want to get into the nitty-gritty of optimising your heat pump, you could do a lot worse than read this thread.

Also read Heat Pumps For The Home by John Cantor. A good read, pitched at many levels, that will help you to run your system more efficiently. However, if this is a new build, then it will also arm you to nail the builders into putting everything right under the NHBC (or whoever) guarantee.

YorkshireJames

Thanks all. It's not a new build l, it's 15 years old and on the original feed in. So I think we would get 50% of our generated energy back through that regardless of our exported amount - am I right? 

QrizB

YorkshireJames said:

Thanks all. It's not a new build l, it's 15 years old and on the original feed in. So I think we would get 50% of our generated energy back through that regardless of our exported amount - am I right? 

Yes, the FITs use deemed export - you're assumed to export 50% of everything you generate, whether you use it or not.

YorkshireJames

Thrugelmir said:

How often does the sun shine when you need your heating on? 

Probably not that often. I'd estimate we need the heating on majority of the time when it's dark. We're on economy7, so that should make things cheaper, or should we buy a solar battery for evening heating?